CHAPTER IV. 
GENEEAL DESCRIPTION ÄND KEMARKB. 
If iu the last chapter or any other part of the book the reader encounter teclini- 
cal terms with wliicli lie is not familiar, lie can ascertain their meaning by turning 
to the Glossary and, if necessary, consulting the plate or plates thero referred to ; and 
he is strongly advised to thoroughly acquaint himself with the meanings of all the 
terms in tlie list of members before proccodiug farther. 
The object of this chapter is to give a general description of the bridges with 
which tliis treatise deals and an explanation of liow the different parts are connected. 
Tlie floor system proper (i. e. tho sliimp, tios, rails and guard rails with their con- 
nections) is described in the next cliaptei.. 
There are but four styles of bridge recommended viz. the plate girder for spoils 
below sixty feet in length, the pony truss from sixty to seventy or eighty feet, the 
single intersection or Pratt truss from seventy or eighty to one hundred and eighty 
feet and the double intersection or Whipple truss from one hundred and eighty to 
tlu’ee liuudred feet. 
The first stylo is so common in Japan that but little explanation is necessary, a 
leferencc to Plate VII rendering clear tlio dcsigu. The special foaturo of the girder 
チ here represented is the inclined stiffening anglo wlxicli bears ux^on the bed plate near 
its inner edge. Its object is to prevent a bending of tlio flange at tlie edge of the bed 
plate. That some such device as this is necessary the author was once convinced by 
inspecting some steel girders on tlio Atchison, Topeka and Santa FeE. E. : tliey had 
bent quite perceptibly at tlie bearings. 
The transverse bracing shown on Plate VII is different from that of the present 
Japanese plate girder bridges. Tho latter is sufficiently stiff for spans up to say 
twenty-fiye feet in length, but the diagonal bracing shown on that plate will be 
found to givo superior rigidity for rapidly passing loads on longer spans. Tlio pony 
truss of wliich some details are shown on Plate IX, is almost the only stylo of bridge 
except tlio plate girder which is usod in Japan. There is considerable difference, 
however, between tliose of this country and those here recommended. Tlio former 
are of the Warron type haviug bottom chords built in a trough shape of plates and 
au gles, and the diagonal struts of two very wide eye-bars trussed. There is no 
lateral system or even side bracing, and tlie passing loads produce bending in the 
0Wer c liords. The style liere recommended differs from the through bridge wliicli 
