612 THE POPULAR SCIENCE MONTHLY. 



by Mr. Alvarado Mayer, a member of the Detroit Fire Depart- 

 ment, in 1809. Mr. L. D. Shaw, of Boston, also introduced a suc- 

 cessful valve in 187-4. Since then there have been a number of 

 different valves in use. Mr. Cornelius Callahan, of Canton, Mass., 

 perfecting one in the neighborhood of 1888. These three are 

 about the only ones in general use to-day. 



It has been seen that the first ladder trucks were introduced at 

 the beginning of this century, and the patterns then adopted have 

 been followed more or less to the present day. Portable escapes 

 were invented by the score, some in the form of extension ladders, 

 others as lazy tongs, and others in the form of cranes, by which a 

 bucket could be raised and lowered. None of these came into 

 general use, because they had not reached a stage of development 

 at which apparatus of that nature could be made light and strong 

 enough to be practicable. The ordinary ladder truck consists of 

 a long frame, with crossbars at different heights provided with 

 rollers. These are equipped with several ladders of different 

 lengths, and an extension ladder. The latter is a combination of 

 ladders that slide over each other by means of a chain and pulley. 

 The whole length is rested against a building, and the center is 

 supported by props. The Bangor Extension Ladder Company 

 and several others make ladders of this kind. The Gleason & 

 Bailey Manufacturing Company, the Stewarts, C. T. Holloway, 

 Seagrave & Company, P. J. Cooney, and some of the engine- 

 makers, manufacture ladder trucks that differ simply in minor 

 details too numerous to describe. 



The aerial truck consists chiefly of an extension ladder that 

 rests on trunnions on a turntable at the forward end of the truck. 

 The extension ladder is raised in much the same manner as is the 

 water tower, and when erect is capable of supporting itself with 

 several working firemen without resting against a building. The 

 Hayes, the Gleason & Bailey, the Arrow, and the Babcock are 

 among those well known. The aerial trucks carry a full comple- 

 ment of ladders. 



The largest ladder trucks are provided with a steering wheel 

 over the rear axle to facilitate the turning of corners, and Mr. 

 Steck, of Chicago, has invented a depressed rear axle which lends 

 stability to the truck, while a lever in place of a steering wheel 

 directs the rear wheels. 



In addition to the regular ladders, a variety of apparatus is 

 carried on every truck. The axes, or hooks as they are called, are 

 too well known to need description. In olden times large, heavy 

 hooks were used to tear down buildings, but these have since been 

 abandoned. It is interesting to note in this connection that as 

 late as 1857 the Scientific American published an illustration of 

 an enormous hook mounted on wheels. The hook was intended 



