257
Let us take the first two experiments in theTable VI. ; every circumstance remained thesame, except the wheels. The engine, witha like weight of fuel and load, travelled 48.8miles with 4-feet wheels, in the time that thesame engine travelled 36 miles with 3-feetwheels, or the quantity of fuel in travelling thesame distance was as 3439 : 2534.
Now, as the weight of fuel consumed willbe a measure of the quantity of steam, and,consequently, of the power expended in pro-pelling the load, we can then, from the quan-tity of fuel consumed in the different cases,determine the total amount of resistance.
With 4-feet wheels the weight propelled bythe engine was 731 cwt. and the quantity ofcoals consumed was 2534lbs.
With 3-feet wheels, the weight was 731cwt. and the coals 3439 lbs. Then, as 2534:3439 : : 731:992cwt. the load which would havebeen propelled by the 4-feet wdieels, with thefuel used by the engine with 3-feet wheels,—the load which the latter took was, however,731 cwt. ; hence, the adoption of 4-feet wheelswould admit of an increase of load equal to992—731=261 cwt. The friction of 731 cwt.,or 9 loaded carriages, is known to be 360 lbs.;therefore, as 731 : 360 : : 261 : 128lbs. the dimi-nution of friction by the use of the 4-feet, wheels.
This reduction, in the amount of friction, isr