262 MOTIVE POWER EMPLOYED

Comparing Experiments XXX. and XXXI., whicli wereperformed by the same engine, and under precisely thesame circumstances, except the load, which, in the former,was with 9 carriages, weighing 731Jcwt., and, in the latter,with 12 carriages weighing 975 cwt., the consumption waswith 9 carriages in travelling 85880 yards 2534 lbs., andwith 12 carriages 1546 lbs. in travelling 40680 yards.Then, as 85880 I 4680 1546 : 3263 lbs., which would

have been consumed in conveying 12 carriages 85880yards. Therefore, the relative consumption of fuel, with 9and 12 carriages, is as 2534 t 3263.

We have previously ascertained the friction of the engineto be 384 lbs., and the friction of each of the carriages tobe equal to 40 lbs. each.

Then 384 + 40 X 9 744 lbs., the resistance of the 9

carriages and engine. And 384 + 40 X 12 = 864lbs., thesame with 12 carriages, which makes the respective rcsist-' ances as 744 : 864. Now, as 2534 : 3263 :: 744 : 958 lbs.,so that the consumption of fuel is greater in the ratio of958 t 864 than the direct increase of resistance by the fric-tion of the additional load.

It was, however, before stated, that thetransmission of an increase of resistancethrough all the working parts of the enginewould create an additional degree of friction,and this will, perhaps, partly account for theconsumption of fuel increasing in a greaterratio than the simple resistance directly, thoughthe different states of the rail will frequentlyhave a greater effect than this upon the con-sumption of fuel.

Comparing these with the experiments on

-*rV".