“sol tific American, established 1845 mY 9 ; - { Scientific American Supplement. $5 a year. eetific American ne Vol. XLIII. No. 1103. 5 NE W YOR K, FEBRUARY 20, 1597. ? Scientific American and Supplement, $7 a year.






OF the many diffieult problems which tax the in gepuity and call up all the resourcefulness of the civil engineer, there are none greater than those which arise in railroad bridge building. Bridge building itself is an art which appeals strongly to the imagination on account of the daring forms to which it gives rise, but it is specially in the field of railroad work that its most brilliant achievements have been recorded. The great weight and the high speed of the moving loads which



have to be carried call for a rigidity and massiveness of porary roadbed or trestles during the buildin,

structure far in excess of the requirements in the bridge for highway travel.

A feature which has rendered the task of the railroad bridge builder specially difficult has been the frequent necessity for erecting a bridge on the line of a railroad without any disturbance of the existing traffic. This has been achieved sometimes by building the new

trusses by the side of the existing trusses and putting |

in the new floor piecemeal ; sometimes by building the entire bridge beside the old structure and transferring it bodily into place in a single night ; in other cases the tracks have been carried around the site on a tem-


1, Mott Haven station. 2. Work in progress near Harlem bridge. 3. Completed structure. 4. Harlem bridge. 5. erection by means of wooden trusses. 8

new bridge.

One of the most brilliant feats of bridge buil record has just been completed on the fan track road of the New York Central Railroad neighborhood of the Harlem River, New Yor where a complete four-track elevated steel st over two miles in length has been built over th of way of the existing tracks without causing a: delay to the traffic.

The tracks of this railroad leave the Grand ( Depot by way of Park Avenue, which forms t) tinuation of Fourth Avenue, and run in a

Fesrvary 20, 2897,


f the

< on 'our-

the Ulty,

False work near 110th Street.

The old and the new.


6 and 7. Work of

< on our. the City, ture ight ur's

( ontral con unel

Feprvary 20, 1897.



_ ———— LS =

yout Fiftieth Street to Ninety-eighth Street,

i. this part of the avenue practically unencum bere \t Ninety-eighth Street the street grade falls rapi and before the present improvements, the trac ere carried on a stone and earth viaduct. They the: idually fell below the street grade and continued ina pen cut until the Harlem River was reaehed. Thi is crossed on a low level bridge which was pro- vick th a center swinging draw, supplemented with an i iary hinged lifting draw. On the far side of

the mvcr the tracks ran through Mott Haven at the stre rade

TI xistenece of a four-track road in the center of Park \venue from 106th Street to the Harlem was a


the lattice girder draw, 106 ft. in span.

The line of travel of the tower having been decided on, rows of piles were driven ; caps were placed on them, and on these 12 X 12 longitudinal timbers were placed. Rails were then spiked down on the timbers so as to form a horizontal sliding way. The tower was jacked up bodily 3 ft. after being stripped of counterweights pete other material so as to make it as light as possible. It is calculated that 100 tons weight were thus removed, of which 85 tons were represented by the counterweights alone. Even when this was done, the residual weight was in the neighborhood of

| 180 tons. When the tower was thus elevated, slideways

hindrance to traffic, and the low level bridge! in continuation of those laid on the outside were placed | about One Hundred and Fifteenth Street.





across the Harlem was an equal obstruction to trave by water. It was accordingly decided conjointly by the city and the railroad that the tracks should be car- ried from 106th Street across the Harlem and for seve- ral blocks into Mott Haven upon an elevated steel structure.

This would restore Park Avenue to the publie use, and in consideration of this the city agreed to contri- bute $750,000 to the cost of the undertaking, the total cost of which has reached over $3,000,000,

It will be seen at onee that the carrying out of such an extensive alteration on a road with the enormous traffic of the New York Central was a work of extreme difficul- ty. The traffic of both the railroad and the river had to be left unobstructed during a period of several years, and it is a tribute to the skill of Colonel Katte and his




corps of engineers that this has been done with com- We present a series of views showing the progress of this work and the various expedients Which were resorted to in keeping the traffic and the hew construction going at the same time.

One of the first things to be done was to builda temporary bridge across the Harlem River pending the erection of the present noble structure. The temporary bridge had to be provided with a draw, and the Federal engineers called for a width which necessitated trusses 106 ft. long. The old trusses of the lifting draw spanned but a little more tha 90 ft. To provide the hew (raw for the temporary bridge, it was determined

plete success.

lirst to move the tower bodily ito position in line with | this was then the only drawbridge, hoisting machinery , outer rollers being 24 in. in diameter, the inner ones

under it. The rails were lubricated with Dixon's plumbago lubricator and the tower was lowered upon them. A six spool hoisting engine with falls of very large size, with great sheave blocks, being 18 in. in diameter, was arranged to draw the tower away from the bridge along the line of the slide. Some apprehen- sion was felt as to the success of the operation, but it was found that the tower might be moved a distance of 8 ft. without interfering with traffic. so it was decided that here, at least, was room for experiment. Accord- ingly, before the final operation, the tower was moved back and forth to distances of a few feet to test the practicability of the operation. When everything was ready the final operation of moving was executed. It was done at night, in order to avoid interruption to traffic. At 12:30 A. M., tte tracks were cut by the rail-


|road company, and the way was cleared for the tower to be drawn out from its position. The foreman in charge of the work, as a signal code, arranged at one motion of his hand to indicate one revolution of the engine. When all was clear, the engine was started, first slowly, and then more rapidly, and in 21 minutes the great mass was moved 54 feet. The railroad com- pany replaced the tracks, and by 3:20 A. M. all was ready for traffic once more. There was absolutely no interruption to traffic. The tower was moved along on its present course until the line of the new tempo rary bridge was reached, when it was moved forward into position and the lattice girders put in position. As

|insure rapid operation. The two bridges, the tower and the temporary slideways are clearly shown in the lower front page illustration.

The methods adopted for carrying out the work on the viaduct without interference with the traffic will now be described. In the upper front page engraving and in Fig. 5 are given views of the work of erection looking north from One Hundred and Seveuth Street. Here the operations included removal of the viaduct carrying the roadbed and its replacement by the new structure. Temporary wooden trestle work was built on each side of the present viaduct and on this the trains were run, reaching the grade of the old road at

This left the ground clear for the demolishing of the old and erection of the new viaduct. When One Hundred and Fifteenth Street was reached, where the'tracks began for part of their. extent to be depressed, another system was adopted. The side columns were put in place, as shown in Figs. 6 and 7, but the tracks being all oceu- pied, it was impossible to put in the center columns. Accordingly wooden trusses were thrown across from the lines of the side columns, and resting on the old retaining wall, and these trusses provided a center bearing for the center ceaieudings girder. In this way, as also shown in Figs. 6 and 7, the full permanent flooring was sustained by side columns and temporary transverse trusses. Now that the new viaduct is in use and the old tracks are abandoned, the center piers will be built, the columns will be erected on them, and after the columns are in place the wooden trusses will be removed.

This procedure, it will be observed, was adopted to keep four tracks in use. But the temporary Harlem

| bridge was a two-track structure. For a short distance | below it, therefore, the four tracks were merged into two lateral ones, as shown in Fig. 2. This left the scene unobstructed, and the viaduct was built at this place without any special methods of construction. | In Fig. 8 we show the relations of the old to the new. |The locomotive is on the old tracks. Along the line are seen the side columns, Ww hose bases are on the street grade, and the side girders, marking the viaduct bed, are seen resting on the columns.

The roadbed is carried on three rows of lattice steel columns, each row supporting plate girders. The in termediate cross trussing is provided by the flooring, besides which there is a transverse lattice girder for each set of columns. This is arranged on the solid floor system, now in extensive use by the New York Central Road on its bridges. <A cross section of it is shown in Fig. 6. It virtually consists of a series of three sided box girders built up of steel plates and angle irons. The plates are 3g in. thickness, and the depth of the vertical plates averages 18 in., with a width of 14 in. The channels thus formed are open alternately above and below, and cover the entire area with a water- tight floor. From center to center of cross space the | distance bridged by the girder floor is 28 ft., giving a | total width of floor of 56 ft.,a plate girder running lalomg each side and one through the center. The | girders are 7 ft. 2 in. deep, and the webs are of steel for the side and , for the center girders. From center | to center of columns is 65 ft. | The trussed flooring is riveted by means of angle clips to the longitudinal central and side plate girders. The rails are clipped to the flooring without sleepers, sound insulating or deafening pads being placed be- neath them. | The great 400 ft. high level four-track drawbridge over the Harlem River is the most monumental feature lof the whole work. The Harlem River is a legal water- way whose importance has been greatly enhanced by |the opening of the Harlem Canal into the Hudson River. A low drawbridge, such as was formerly in use, was not only an obstacle to vessels, but the necessity for its periodical opening interfered with the running of the trains. The new bridge is so high that the ma- | jority of vessels using the Harlem River can pass under it. Thus, while it can be opened, it will be rarely that | the necessity for doing so will arise. The bridge, by its high level, will at once improve the conditions of railroad and river traffic.

To the north of the draw span there are two fixed en the one farthest north being 131 ft. 444 in. and the next 185 ft. 44¢ in., these trusses being respectively 26 ft. 3\4¢ in. and 30 ft. 103¢ in. high. The draw span, measured from center to center, has a length of 389 ft., its length over all being about 400 ft. Its breadth is 58 ft. 6 in. from center to center of the outside trusses, being carried by three trusses, one central and two lat- eral ones, the center one being the heaviest. These trusses provide two clear ways across the bridge, each 26 ft. wide, and in each of the trackways are two tracks. At the center the draw span is 64 ft. high and at the ends 25 ft., all measurements being taken from center to center.

The 131 ft. span weighs 475 tons and the 185 ft. span 850 tons, while the great draw span weighs 2,500 tons. It is of the pinned truss construction, and some idea of its dimensions may be obtained from the fact that the principal top pin of the hip, next to the tower, is 11 in. diameter, while the bottom pin of the center truss next the tower is 12 in. in diameter. These pins are all steel forgings, turned to shape. Other dimen- sions are worth citation.

The bottom chord of the bridge, which chord has a double role to fill—acting at once as a truss member when the bridge is open and also as a girder between the successive panel points, to support the weight of passing trains—is 48 in. deep, The tension members, extending from the top of the tower tothe hips of the girders, consist each of eight bars of steel 10 in. by 154 |in., representing in the aggregate a cross section of |nearly a square foot of steel. One could easily go through the whole structure and quote the dimensions, but we are merely giving enough to afford an idea of its great size. The floor of the bridge, which is ear- ried direetly by the bottom chords, is of the same solid floor system as that used in the elevated way, the troughs being 18 in. deep. The rails are laid direetly on this floor.

The draw span of the bridge is carried on two con- eentric drums 4 ft. apart, the outer one being 54 ft. in diameter, the inner one 46 ft. in diameter. Under each of these drums is a circle of seventy-two cast steel rollers turned to a perfectly true conical alignment, the

| the temporary bridge, and to use it to raise and lower |of double the power of the original was put in, so as to )




20/7, in. in diameter, and both being 10‘, in. face entire weight of the draw span when open rests upon these 144 rollers The outer circle of rollers can be seen very clearly in the different cu(s representing the bridge especially in the « the center bearing. Of only the outer can be The drums are staved together radial lattice struts, and the rollers, although journaled, so that they appear to be wheels, really act as true rollers in the operation of the bridge On top of the drums is a eight steel beams, parallel and of varying length, represent ing chords of the circle of the drum, and on these beams the draw span, when open carried, so that there are provided thirty-two bearing points on the two drams for this set of and for the draw span All this is clearly shown in the view of the bridge and in the small view of the bearing Phe drums feet high.

Merely to keep the bridge bearing in position ter pivot casting is supplied, but the entire weight of the draw span, when open, comes upon the rollers. The center casting will no work to do in earrying weight turned by steam, the engine house being situated the tracks within the central tower of the Here are installed two oscillating, double eylinder en made by Edwards & Company, of New York. The cylinders are 10 in. in diameter and have 7 in. stroke :

The weight of the draw span is only partly taken up by the central bearings when it For each end there are levers arranged somewhat like toggle joints, which are operated from the center tower by steam power When closed the levers are drawn together so as to take of the weight of the ends so that when the draw span is closed and the bridge is ready for the passage of trains the draw span acts partly as two through trusses and partly two can tilever arms. When the draw span is to be opened,

showing drum sixt

me course seen

by een

series ot

is girders are


have absolutely The bridge is above structure


is closed







1103. Fesrvary 20, 1897 ,

representation by interested parties who seek to retard | simply a steam pipe from the boiler to the comp!

the progress of a competitor of superior merits.

The upon a general discussion ofthe applications of com pressed air to thecity and suburban service, but will confine himself to an effort to answer some prominent objections.

The late Franklin Leonard Pope, after thorough in vestigation, expressed the opinion that electricity could not compete with compressed air for traction purposes in city and suburban service ; but compressed air does not invite antagonism, but rather seeks co-operation with electricity. Both systems can be track, and economy can be secured by compressed air motors at night and at hours of light traffic when the electric plant cannot be worked to full capacity, and the same remark is applicable to the cable lines

Specialists who are thoroughly saturated with electricity that they cannot perceive merit in any other constantly affirm that the trolley is less expen both in installation and in operation, than com pressed air. The writer has no right to give to the apes actual figures of cost which might interfere with the A merchant is under no obligations to publish to the world the cost of his goods and sell them with no addition to the price to cover ex penses, services, interest, rent, depreciation and profits : but comparisons can be made to show that a com pressed air equipment can be provided at a cost not ex ceeding that of the trolley, and with such evidence in vestors should be satisfied in view motors are independent and furnish a much better ser than any other system now or heretofore in use.

Power Required.—Ordinary electric ears are usually provided with two twenty-five horse power motors; but the allowance at the central station is twenty-five horse



svstem sive,

business of the licensees


writer, in this article, will not attempt to enter

used upon the running

of the fact that air |

and all shafting, belting and other mechanical ances are dispensed with.

The colupressor and boilers would offset the and boilers in the electric system, and it would possible to furnish any good reason for the that the power plant of a compressed air system cost more than that of an electrie system for equi, service; but, if any doubt should be still entert; and claims for superior economy of electricity cont to be asserted, a complete answer can be given ir fact that responsible parties will consent to furn compressed air plant at as low a price as partir equal responsibility will agree to furnish the ek plant for the same service, and it is understood the proper parties will give proper and sufficient antees as to the amount of air used by their cars w! will remove any element of uncertainty and unnecessary to give detailed figures to superior economy of the svstem

As to operating expenses, an estimate made by a competent engineer, familiar with both systems, gives a difference ot over three cents per car mile in favor of compressed air, after allowing for interest on plant, taxes and general expenses.

The comparison has been made with the cheapest the electrical systems, the trolley If it desired to secure the highest efficiency combined with the great est economy, no intelligent engineer who has made a eareful examination of relative merits could think recommending any underground electric. If the object is to inflate expenses as a basis for the maximum possible issue of bonds, then the anderground elect: will fulfill requirements ; but every dollar expended in conduits, insulators, conductors and street construe- tion is absolutely thrown away, and the late blizzard in New York has demonstrated that snow falling


rende prove




iis ili

kil 3

Fie. 11.—NEW FOUR

inches clearance not all that is

lso to be swung used to secure a

the levers are moved so asto give 3 for the ends of the bridge. This needed, The ends of the rails have a upward to clear the alignment ¢ perfect joint for the passage of trains

The reverse of these operations is carried out when the span is closed. A structure is shown at the end of the viaduct it meets the bridge. This represents architecturally a abutment, but really it is of little utility, having placed there almost entirely for architectural reasons

The draw span, turntable and fixed spans were built by the King Lron Bridge Manufacturing Com pany, of Cleveland and New York

The steel viaducts were built by the Company and the New Jersey [ron any, at a contract price of $1,500,000. The Harlem ~aa crossing has

about $1,000,000, the work at Mott Haven, $500,000, the work of the via duct piers, $100,000, the tracks, $100,000, making an aggregate cost two miles of work of over $3,000,000.



masonry where stone


Elnira Bridge and Steel Com

cost masonry temporary for the whole


A LEARNED judge, at a the clatter of tongues of some at an adjoining table, when he turned to them with the remark, ‘Young gentlemen, | am really astonished that men of your tender should have accumulated such a vast amount of ignorance as vou have exhibited on the subject von have been attempting to diseuss.”

The ignorance that has been accumulated on the sub- ject of compressed air motors has been vast, and it is continually cropping out in newspaper articles as re ported in interviews and otherwise; but doubtless much of this gnorance has been due to mis

* Engravings of the Ha vated Railroada, New January 3, 1807,


Consulting Engineer


restaurant, was annoyed by students of a law school



apparent 1

as applied to the Ele SCIENTIFIC AMERICAN of

<i in

wrk | City, appeare


power for each car on the line, of transmission being five miles and the voltage being 300 volts at the ear.

The average power required for the propulsion of an electric car on a comparatively level road, as the West End Road, of Boston, was determined by Prof. H. G O'Neil, in a series of accurate tests, and found to be i24¢ horse power, rising at times, in overcoming great resistance, to 58 horse power.

Whatever the system, ear be the same for all when resistances are equal.

The loss in the transmission of the electric power from the prime mover to the rail is very great. A writer in the Engineering News of October 17, 1895, gives the loss in detail, with a resulting efficiency of s7°2 per cent.

An eminent English engineer, in a recent investiga- tion of one of the prominent electric roads of this coun try, found the figures given by the manager of the road to indicate that there was a net efficiency in the system of only 22 per cent.

In the transmission of compressed air there is no The efficiency at the end of 10 miles is as great as at the start, and there is practically no leakage. A reservoir charged to 2,000 lb. persquare inch was al- lowed to stand one year, when it was found to have lost in pressure 10 per cent., a loss which may have been due to the difference of temperatures, and not to leakage.

It should need no demonstration by figures, there- fore, to prove that a given amount of power at the power house can be transmitted to the car on the rail with at least as little loss by compressed air as by electricity.

The plant for the generation of an electrical horse power costs much more than for a horse power of com- pressed air.

The reason of this can be readily explained. An electrical horse power requires a prime mover, belting, shafting, dynamos, transformers, converters and other wachinery, while a compressed air plant



the maximum distance | through the slot destroys the insulation

: | the power required to run a must be sufficient to overcome resistance and must |

requires |


and blocks the track.

As to comparative danger in the two systems, it is unnecessary to refer to the deaths of men and horses caused by live wires and the conflagrations directly caused by electricity, or the damages increased by ob struction to the free use of fire apparatus, or the de struction of gas and water pipes by electrolysis. The

| daily press keeps the public fully informed in regard to

these casualties. On the other hand, it ean be confi- dently asserted that compressed air presents no ele ment of danger.

The newspapers published an interesting interview witha distinguished member of the traction compan) in which he is reported to have condemned the Hardi: system in consequence of the reservoirs under the floor charged with air at 2,000 Ib. pressure. This the favorite objection of parties who are interested in other systems, and no matter how completely it may have been answered, it continues to be repeated.

Paradoxical as it may seem, the fact is, that air sufficient for a run of a given distance, 2,000 pressure per square inch is much safer than 500 Ib.

The explanation is simple. It is the practice of a competent engineers to make a careful computation of strains and allow a margin of safety that will be saf under the most exacting conditions of service.

After an extended correspondence with manufactu rers of reservoirs in Europe and in the United State~ the contracts for Hardie reservoirs have been given ex elusively to one foreign establishment. The condition- required to be fulfilled were uniformity in thickness. homogeneity of metal, maximum ductility and an elas tic limit of about 35,000 pounds per square inch. Thes reservoirs are tested to 4,000 pounds per square inc within the elastic limit, but are not charged in ordinar service to more than 2,000 pounds. The strains whic cause ay re have been found to be over 6.000 pounds, and the elongation before rupture is of an inch in circumference of twenty-eight ine shes.


with Ib

The margin « safety is so great that the pressure would be requir to be increased to over 4,000 pounds per square inc

v6, I Sor, pli- ine th- . on ild \ “nt bi ed iT ue in the a le of ie ‘re if = ir- Which le it t he I a gives re f lant, est of d to reat hue a ik [ e 1h ie n zard ling re

| |

ae Pie

Fesrcary 20, 1897, SCIENTIFIC AMERICAN SUPPLEMENT, No. 1103. 17627 bef langer of rupture would be possible, and if rup- | supplied with a pet cock at its lowest points and; The cost of repairs of the Hardie motor has been es- ture wild occur, the air would instantly eseape, and, | drained off. timated by competent engineers at twenty-eight hun- in co: ~equenee of the ductility of the material, ne pieces| Considerable space has been given to this explana- | dredths of a cent per car mile, or at most one-third of eou e detached. If material of high tensile strength | tion to prove that the Hardie reservoirs are absolutely |a cent. The, general manager of the American Air wer ed, it would be more brittle, and in case of rup-| safe, and more safe under all conditions and risks of | Power Company, when asked what had been the ex-

ture im an excessive charge, pieces might become de- und cause injury; whereas, under the conditions

| 4 . a r | service than reservoirs would be if designed to work under a pressure of 500 pounds.

pense of the repairs on the Hardie motors, running on One Hundred and Twenty-fifth Street, during the five

tac! ~ - ; , . nal the Hardie reservoirs are absolutely safe. It is not to be expected, however, that the most con-| months of service, replied that he had not figured it W are reservoirs charged with 2,000 pounds pres-|clusive demonstration will prevent continued misre-| exactly, but that it did not begin to be as much as a sul wre safe against rupture rather than others| presentation by interested parties. quarter of a cent per car mile, which may be too low eharced with 500 pounds only ? Objections to the Hardie Motor on the Ground of | for an average in continued use. Siuply beeause the same factor of safety would be! Exposed Machinery.—It has been said that the motors! In the attempt to save a portion of this quarter of a q A= 4 - Bees -X) 3 ofS | =. 7 i ~ a i os ce | ~ A a ee ae ee, , DY | ) ba) SPS ee | used in both, and the lower pressure would admit of a of the Hardie and Mekarski type have exposed machin-|cent, which is less than one-fiftieth of the total car much lower limit of variations ery, outside rods and eccentrics exposed to dirt and| mile expenses, it is proposed to substitute geared On an ordinary motor car there is room for only 50 liable to wear. | motors, eubie feet of reservoir capacity, and while 2,000 pounds This objection will be considered. There is sucha} The attempt recently made to supersede the Hardie pressure would give, as is shown on 125th Street, arun thing as Jumping out of the frying pan into the fire, | motor by competitive geared motors has involved an

of seventeen miles with 400 pounds pressure in reserve, a reservoir under 500 pounds pressure would limit the run to about four miles

If reservoirs calculated for 500 pounds should, in order to increase the length of run, be charged 500 pounds more, the danger limit would be approached, but reservoirs designed to carry 2,000 pounds could have the pressure increased 500 pounds more and still be 1,500 pounds within the limit of perfect safety.

An air motor has ne.ther firebox nor boiler, which are the principal sources of eXpetise ln repairs ; the 1 eser- volrs are not exposed to any corrosive influences, and their duration should be indefinite. The interior is coated with a cOllposition recommended by x. P. Moore, of the American Society of Mechanical Engi neers, Who has given an exhaustive study to the sub- ject of the protection of iron and steel surfaces against corrosion, and who has presented four valuable papers on the subject, but, were there no protection, the oxi-!

and an imaginary evil may be avoided by introducing others of a far more expensive and serious character,

What is understood to be desired is a motor that can be substituted for the electric, using the same standard gearing, the same body, and the same trucks, simply adding reservoirs under the floor, and if such a motor cannot be secured, it is said the underground electric should be adopted.

Direct application of power is more efficient than |

indirect, and a long stroke reciprocating engine, cut off at an early point, and using air cr steam expansively, secures the greatest known efficiency with a given expenditure of the elastic fluid.

The full effect of independent motors attached to separate axles cannot be secured unless there is perfect synchronism. Franklin L. Pope states that in a test made by him the efficiency of one motor was greater than with two.

It is claimed by competent

mechanical engineers



dation of the interior surface, if any progress were | made, would be very slow, for the reason that air under Very hizh pressures carries no moisture with it. It is a property of air, not usually known, that the capacity

for moisture depends upon volume and temperature, and is independent of density; consequently, when 136 eubic feet of free air are compressed into 1 cubie foot, the resulting cubie foot can contain only the ;}, part of the

Water that the air contained before compression.

his moisture is collected into a separate receptacle

that ordinary gearing would reduce the efficiency of a locomotive from 15 to 20 per cent. as compared with the usual direct applications of the power.

When tens of thousands of locomotives have been running for half a century through dust, mud and sand, the objection to the Hardie motor on the ground of exposed machinery seems decidedly frivolous. But to meet the objections an attempt will be made to show what is the expense of keeping the exposed machinery in repair and the cost of the proposed remedy.

increased consumption of air of over 200 cubie feet per

|milerun, There is no rotary or short stroke recipro- leating engine or geared motor now known to the writer that could be substituted without a largely in- creased consumption of air.

The total cost of repairs of machinery of the Hardie motor for one year at three-tenths of a cent per car jimile would be $173. Geared motors would no doubt increase the cost of repairs and the consumption of air, and it is reasonable, therefore, that even if a saving could be effected in using inclosed gearing instead of ordinary locomotive machinery, it would be secured by introducing new elements of cost in inereased con- sulption of air that would greatly exceed the saving.

It is understood that if the attempt now being made to invent a satisfactory geared motor should continue to prove unsuccessful, then the adoption of the under- ground electric will be still more persistently urged. | If, as previously stated, the object should be to adopt

a system that will inflate cost to the greatest extent, allow the greatest number of bonds to be imposed upon a credulous public, and by expensive contracts secure the largest margin of profit for contractors, then the underground electric is that which will best fulfill these conditions, but if economy in cost of plant and of operation is desired, the underground electric will never be adopted.

No system that is dependent for successful and unin- terrupted operation upon the integrity of its connec-


a distant source of power, like the electric the advantages that uloption of independent mo

tion with and cable ean be secured tors

If underground electric construction is reeommended as a means of utilizing present trucks and motors, in stend of expending capital for new construction, the effect will a large expenditure to secure a small saving in plant with a large in cost of nain tenance

The cost of the Lenox underground electric is said to have been $140,000 per mile double track, and in an in terview with Mr. Vreeland, the president, by a Herald reporter some time it given his opinion that the system was not to a line doinga heavy business, that it required days to locate a fault that eould, when discovered, be corrected in a few minutes. In a blizzard in New York the underground electric was blocked by snow drifting through the slot, by which the insulation was impaired The cable lines blocked to some extent, while the compressed air motors on One Hundred and Twenty-fifth Street to schedule and gave satisfac tory and uninterrupted service

Returning to a former standard of comparison, if a double track of ten miles should be operated by the underground electric system, the cost of which will be taken at $1,000,000, the interest on this sum at 6 per cent. will be $60,000, the car 160 miles per ear per day 1,728,000 miles, and the interest ear mile 34 cents, Add to this the repairs i cents, and the repairs on line, 0°43 cent, and will be cents

If this expenditure should be made in order to utilize the present motors and avoid the necessity of the new motors and trucks required by the adoption of com pressed air, it is to be observed that estimates by com pevent engineers of the cost of trucks and machinery for air motors, omitting reservoirs, give a lower sum than for electric, and wheels and axles and some other por tions might be utilized in making the change; but if the change should involve a total loss of all parts of the eleetric motors except the bodies, and no credit be given therefor, a full estimate for tracks and machinery for 30 air motors would be $30,000, the interest on which would be $1,800, the annual mileage 1,728,000 miles and the interest per car mile | mill, Add for car repairs 3 mille, which repairs on air motors, from present experience, and the result is 4 mills, as against 5°58 cents per car mile under the underground electric syste.

This estimate

ean possibly

by the


be Increase

Was adapted sometines

ago is


were also



mileage at per cars, |

the total

on i


is in excess of

bas been based upon a small equip- ment of 30 cars. If 60 cars were run on the 10 miles, the interest account per car would be reduced. But Mr. Vreeland formerly said, in an interview published

in the Herald, that the system is not adapted to a line




been proved by years of trial to be a complete success, | and which has been examined, tested and reported upon by the best engineers and experts of the country without an unfavorable report in any instance.

If it be true that the fittest must survive, the time seems near at hand when the superior merits of com- pressed air for traction purposes will be recognized, but the greatest obstacles to success are probably found in the fact that the popular recognition of the merits of compressed air motors has induced inventors, with-