Memoirs of Benjamin Franklin · Benjamin Franklin
B. FRANKLIN.
After our return to England, as often as I happened to be on the Thames, I inquired of our watermen whether they were sensible of any difference in rowing over shallow or deep water. I found them all agreeing in the fact, that there was a very great difference, but they differed widely in expressing the quantity of the difference; some supposing it was equal to a mile in six, others to a mile in three, &c. As I did not recollect to have met with any mention of this matter in our philosophical books, and conceiving that if the difference should really be great, it might be an object of consideration in the many projects now on foot for digging new navigable canals in this island, I lately put my design of making the experiment in execution in the following manner.
Water 1-1/2 inches deep. 2 inches. 4-1/2 inches. 1st exp. 100 94 79 2d " 104 93 78 3d " 104 91 77 4th " 106 87 79 5th " 100 88 79 6th " 99 86 80 7th " 100 90 79 8th " 100 88 81 --- --- --- 813 717 632 --- --- --- Medium 101 Medium 89 Medium 79 I made many other experiments, but the above are those in which I was most exact; and they serve sufficiently to show that the difference is considerable. Between the deepest and shallowest it appears to be somewhat more than one fifth. So that, supposing large canals, and boats, and depths of water to bear the same proportions, and that four men or horses would draw a boat in deep water four leagues in four hours, it would require five to draw the same boat in the same time as far in shallow water, or four would require five hours. Whether this difference is of consequence enough to justify a greater expense in deepening canals, is a matter of calculation, which our ingenious engineers in that way will readily determine. * * * * * _To Oliver Neale._
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