232 DISCUSSION ON 
The original form of the flange was shown, and the effect of 
curvature was to cut into it, reducing it (as shown by the dark 
section), rendering it unsafe for the road and apt to lift over the 
rail. ‘Tyres in that condition had to be brought into the shops 
and the flanges restored by turning off the metal of the tread in 
the manner shown by the lower section; the space between the 
two lines being absolutely wasted material. Sometimes the tyres 
had to be reduced more than an inch in diameter in that manner, 
and the loss was entirely due to curvature. He was afraid the 
idea that curvature did not destroy tyres was a phantom, often 
responsible for inducing the constructive engineer to adopt curves 
in many cases where, by a little extra expenditure, straighter lines 
might have been used. 
There was another remark by the author, which he scarcely 
understood. It was “an engine should be as like a snake as 
possible, using all its length for adhesion and propulsion.” But 
that statement seemed to be contradictory in itself. An engine 
which used all its length for adhesion and propulsion must 
necessarily be a coupled engine, all its wheels must be coupled, if 
_ they are used for adhesion ; and it must be without any bogie or 
flexible wheel base. But probably the author intended to direct 
attention to some of those abnormal machines, such as the 
‘‘ Fairlie” locomotive, which made some stir twenty or twenty” 
five years ago. That machine was really a double locomotive; it 
consisted of two complete engines, entirely independent of each 
other, except that they were pinned to one boiler. Such arrange- 
ments had been found to be deficient, and they were consigned to 
the scrap-heap long ago. The author incidentally referred to the 
engines used on the New York elevated railway as machines 
which possessed the virtue of being able to work readily round 
very sharp curves. They certainly could turn round very sharp 
corners, but then they were mere toys of locomotives, about as 
powerful as our tramway engines. They did not weigh seventeen 
tons in working order, which was less than the load on the driving 
axle of ordinary sized locomotives, and the adhesive weight of the 
