spans, where the strains are great, necessitating a large area of section ( placed 
mostly in the above plates ) the centre of section approaches the plates very rapidly. 
27’¢ rivelted system has of necessity, so m'any inperfections of design } of workmanship 
an ^ ma ^rial f in contrast with the above [pin-connected], that, to obtain anything ap- 
pJOciching equal strength on the same specification t it should only he used with a higher 
factor of safety. It is probable that this difference is not less than 20 per cent; so 
tlmt when a pin bridge is called for, having a factor of five, a rivefcted bridge cannot 
bo considered as approaching the same strength unless it is proportioned with a fac- 
tor of siiv. The fact that a rivetted bridge is stiff or that its deflections may bo small 
under a test, is no evidence of strength, which last depends upon other considera- 
tions than those applying to stiffness n 
These remarks of Mr. Boiler's are intended for lattice bridges, in ■which the web 
members are rivettod to the chords, but they ai*c most of them applicable to the 
lower chords of the Japanese bridges, which are made continuous from end to end of 
span by rivefcting. Tlie Japanese truss bridges, although Warren girders, are not 
wliat may be properly termed pin-comiectetl bridges, for the office of the lower chord 
pins is merely to transfer the web stresses to the chords. 
The inspector would next turn Lis attention to details and would notice the apo- 
logies for stay plates containing one rivet at each end and spaced about three feet 
apart, which connect the opposite flanges ou the under sides of the top chords ； the 
lieads on the main diagonals formed by rivet ting a piece of plate on each side of the 
bar at the eye ； aud the smallness of the connecting plates and the pancity of rivets 
at; tlie joints in the chords. 
There is one tiling that he would be sure not to overlook, and that is the absence 
^ a S uarc ^ rail or any arrangement to prevent a derailed car or locomotive from go- 
ln o through the bridge. This is indeed a grave fault, for derailed cars have been 
lvnown to go long distances before the accident lias been found out : the reason that 
no Japanese bridge has as yet been destroyed in this way is probably due to the ex- 
cellent quality of the road bed and to the absence of severe frost. 
Tlie trouble with most English bridges and consequently with those of this 
country is tliat they aro designed by railroad engineers, wlio have not made a special 
study of bridge designing, and are therefore incompetent to do the work entrusted to 
them. 
Although I have made many inquiries I liavo been unablo to ascertain anything 
certain concerning the designing of the Japanese bridges, in respect to either the as- 
sumed loads or the intensities of working stress, tlio invariable answer to my ques- 
tions being that u the bridges are made according to designs prepared by foreigners.* 5 
One engineer did tell me that 4.110 assumed live load for all cases was one ton ( 2240 
pounds ) per liueal foot. If sucli be the case, the short spans aro too weak. 
Thanks to tlio courtesy of Mr. Takanobu Köno. M. 1^, and Mr. Yoshimura of the 
ICöbu Daigaku, I have been able to obtain the actual weights of iron in a number of 
t lie «I apanese bridges. Of these I have chosen the following for tlie purpose of com- 
p arison "witii tlie bridges designed for this treatise. 
A single track lattice girder of sixty- seven feet span on tlie Kobe and Osaka line 
