ON RAIT.-ROADS.

253

eumstance remains the same, being as the spacepassed over; then, as 63280 yards, the spacepassed over in Experiment XXIX : 25341bs.the coals consumed : : 85880 yards, the spacepassed over in Experiment XXX : 3439lbs.the coals which would have been consumedin Experiment XXIX in traversing 85880yards; the relative consumption of coals willthen be

V 3-fect wheels / distance and load ( 2439 lbs. •

No. T. Engine < / the same in each <

f 4-feet wheels j Experiment, C 2534 lbs.

From which we have the relative consumptionof fuel by the same engine, with 3 and 4 feetwheels, as 3439 :2534, which is nearly in theinverse ratio of their respective diameters.

It may appear paradoxical to some, that, byincreasing the wheels, the engine was enabledto pass over a greater distance without any lossof effect; and might lead to a supposition, thatby making the wheels extremely large, itmight travel with very little pow er at all ; but,when duly considered, it will prove very con-sonant with reason, and what, from the natureof the action of these machines, we might havebeen led to expect.

Before, however, explaining this, it will benecessary to ascertain the amount of the wholeretarding forces opposing the motion of theengine, viz. the friction of the engine, and the