Note 8 — Chapter III · ON THE CONSTRUCTION OF LIGHTHOUSE TOWERS.
Reading edition
This reduction seems to be warranted by the results of some experiments of Bossut.
[9] This is the product of 240 tons, by the ratio of 2·5.
[10] L’art de bâtir.
[11] The number 168 is ⁷⁄₁₀ths of 240, which is the weight of the cylinder, reduced by the weight of an equal bulk of salt water; and 74 is the excess of 242 tons, the pressure of the waves, above 168, the amount of friction.