which is the equivalent of the weight of a column of liquid whose height is equal to what we call the kinetic height. Apart from the tests on the plate submerged in the current of a river, he also proposed another one for plates in air flows, although he presents the apparatus by itself without any reference whatsoever to a measurement. On comparing the values of resis- tance in the air and water, he established that the effects were proportional to the densities, another rule which also would persist. On the other hand, in the tests in water, this impinges on the plate perpendicularly, while in the case of air, it does so at an angle of 45, thus breaking up the impinging force into two components.