290 KANSAS CITY REVIEW OF SCIENCE. 



ty-five feet with a width of 300 feet. The work is done with bucket and chain 

 ■dredges, exceedingly well adapted to the purpose. Some of the buckets are 

 armed with great steel teeth which excavate the solid rock (geologically, Utica 

 slate, but compact rather than slaty in its structure), detaching and bringing up 

 blocks sometimes containing several cubic feet. 



If anything of the kind could astonish us in this fast moving age, it would be 

 the rapidity with which, during the past half dozen years, the construction of 

 elevated railroads in New York, and to some extent elsewhere, has gone on. It 

 is of little use to find their aggregate length, for in a few weeks any such estimate 

 must be corrected. There may now be about thirty-three miles of such roads, 

 all double track. The average cost, including stations and equipment, has been 

 about $800,000 per mile. 



One of the cases in which a new contrivance effects a great revolution, is 

 that of the elevator. This has been in use for perhaps a quarter of a century at 

 the Continental Hotel in Philadelphia, and in a few other places, but is now 

 coming into general use, and is revolutionizing the mode of building in our great 

 cities, especially in New York. A block of buildings is not now extended along 

 a street as formerly, but is set up on end, and a highway to the different houses 

 or parts of the block, is not horizontally along the sidewalk, but vertically through 

 the elevator shaft. Sky-room is cheaper than earth-room. It is said that a lot 

 on the corner of Wall and Broad streets was recently sold for over $320 per square 

 foot, or at the rate of $14,000,000 per acre ! Equal to the surface covered with 

 silver dollars five deep. These stupendous buildings will give engineers and 

 architects much to look after in the way of foundations. 



This reminds us of the Holly plan, in limited use elsewhere for several years, 

 now going into extensive use in the city of New York, of dispensing with private 

 fires for heating, and private boilers for generating steam; and furnishing 

 heat and steam power for a considerable district from one great central set of 

 boilers, piled boiler over boiler, tier on tier, for 120 feet in height. This is one 

 of the operations most characteristic of the present time. Nothing is to be done 

 now by the individual, but everything by some institution, or corporation, or 

 central power, or great firm. Man has ceased to be a unit, and become only an 

 atom of a mass. With the disappearance of the things themselves, the dear old 

 phrases ''family fireside," and "domestic hearth," are rapidly disappearing. 



Mr. Shinn and the engineer, Mr. Emery, have kindly given me some par- 

 ticulars respecting this transportation of heat and power, but I can only refer to 

 one or two points. The first and most obvious necessity is to prevent the escape 

 of the heat. This is done by enclosing the steam- carrying pipe in a small brick 

 tunnel, with a flat cover on the top ; and fiUing the space around the pipe, from 

 the bottom of the tunnel to the flat covering above, with mineral wool, which is 

 found to be an excellent non-conductor. It is made by blowing a jet of steam 

 into a stream or jet of melted furnace slag. The arch and covering of the tunnel 

 are plastered over with asphaltum, to exclude all moisture. The loss of heat is 

 said to be very small. One of the great difficulties comes from the expansion 



