. The street railway review . and areseven inches deep. The drill is operated from 5 a. m. to9 p. m. by two shifts of men. The number of holes drilledper day varies from 300 to 700 according to the nature ofthe concrete. Each hole is loaded with one-tenth poundof 40 per cent Aetna dynamite. Common sand is usedfor tamping and from 8 to 12 holes are fired at once bymeans of a magnet. In order to prevent all danger fromflying particles, an old car especially prepared for thispurpose is placed over the holes before shooting. Thiscar has been strongly braced and floored with ties, and isprovided wi
. The street railway review . and areseven inches deep. The drill is operated from 5 a. m. to9 p. m. by two shifts of men. The number of holes drilledper day varies from 300 to 700 according to the nature ofthe concrete. Each hole is loaded with one-tenth poundof 40 per cent Aetna dynamite. Common sand is usedfor tamping and from 8 to 12 holes are fired at once bymeans of a magnet. In order to prevent all danger fromflying particles, an old car especially prepared for thispurpose is placed over the holes before shooting. Thiscar has been strongly braced and floored with ties, and isprovided with heavy side-boards which are lowered be-fore firing, thus forming a completely closed space overthe charge. Blasting with this outfit has been done inthe narrowest streets in the heart of the city and up tothis date no accident of any kind has occurred. Consid-erable experimenting was done in order to find out howdeep to drill the holes and how much dynamite to quantity adopted will just shatter the top of the con-. crete so that it may be picked out in large pieces, leavingthe concrete unbroken twelve inches below the surface,thus affording a solid and substantial foundation for theties. The bottom of the conduit is filled with fine, brokenconcrete, mashed in and thoroughly rammed, before theties are laid in the trench. Having prepared the roadbedin this manner there remains beneath the ties a solid blockof unbroken concrete, of the width of the track and overtwo feet in thickness. After excavating the trenchthe track is laid, joined together temporarily by fishplates, tamped, lined, .surfaced and completely finishedin every particular before the joints are cast. The ap-paratus for casting the joints consists of a cupola furnacemounted on a heavy truck. The cupola is two feet in di-ameter, brick lined, and the blast is furnished by a No. 5Sturtevant blower, driven at 1800 revolutions per minute,by a 5-h-p. motor, which receives its current from thetrolley. The cupola
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Keywords: ., book, bookcentury1800, bookdecade1890, booksubjectstreetrailroads
