304

MOTIVE POWER ON

more capacious one, induced the reporter togive the subject particular attention ; and, bymeans of experiments made with the dynamo-meter, so far as lie had an opportunity of car-rying the experiments into effect, the differenceappeared to be at least one-fifth in favor of thegreat canal.

Under these circumstances, I shall take theperformance of a horse equal to that of 30 tonsupon a canal, which is the greatest 1 have seenassigned by any one, and we have previouslyfound the energy of his power equal to 10 tonsupon a Rail-way; which will make the relativeperformances as 3 : 1.

I am not acquainted with any experiments,made on a practical scale, to ascertain the ratioof the increase of resistance, either with differentweights, or with the same load moved at dif-ferent velocities, upon a canal; but it is as-sumed, by all writers on the subject, as a lawof hydrodynamics, which appears unquestion-able, that the resistance at least is propor-tionate to the square of the velocity.

Taking these premises as sufficiently esta-blished, the Diagram III. (page 183) will re-present the resistances at different velocities :and the following Table will shew the relativequantity of work performed by horses draggingboats on canals, and carriages upon Rail-roads.