The Resistance of the Air

Abstract

THE object of my notice was to give a general account of Le Dantec's and Canovetti's experiments, and certainly not to deliver judgment on those delicate questions of priority which are mainly of personal interest. The “law of perimeters” being so noticeably put forward as a new result, I could do no less than cite the views of Le Dantec and his referee, between whom and Hagen or his advocate “C. A.” the matter must rest. There is surely a contradiction of terms in your correspondent's expression, “that dissipation of energy that occurs in the ideal perfect fluid, and which has been called convective friction in the above-mentioned treatise and elsewhere.” A fluid which dissipates energy, especially by means of anything called friction, is not an “ideal perfect fluid” according to universally accepted definitions. As to the “scientific interest” of determinations, not only of the aërial resistance of a square metre, but also of the weight of a cubic centimetre of water, the so-called mechanical equivalent of heat, the electrical resistance of a copper wire, the E.M.F. of a Clark cell, or any other physical quantity whose value is affected by various conditions, this surely is a matter of opinion; but the great amount of attention which is now devoted to accumulating statistical data of this class is sufficient indication of a general consensus of opinion in favour of such researches being regarded as valuable from a scientific standpoint.