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Published online by Cambridge University Press: 27 November 2017
If one reflects on the great army of scientific men who are at present studying the subject of the motion of planes, at an angle, in fluids, it is very remarkable that the work of Avanzini on this subject should have escaped notice. All that appears to be known about this diligent experimentalist is in reference to what is known as “ Avanzini's law,” in relation to the position of the centre of pressure on a moving plate. This law is quoted by Professor Bryan and M. Alexandre See (to quote two only of the most eminent writers on the subject), but they omit to say from whence they get the formula. M. Alexandre See, in a private letter, has kindly informed me that “ je crois qu'on a appele ‘ Loid ‘ Avanzini ‘ une loi qu'il n'a jamais formulee lui mime., mais qu'il a etudiee.” Whatever Avanzini may have said on the subject is probably to be found in the Memorie della Academia di Padova, but the volume containing his memoir does not appear to be in England; in any case 1 have not been able to find it.
page 192 note * Experiments in Aerodynamics, 1891.
page 193 note † Il faut observer que le centre de pression du Fluide est ou doit étre censé au centre de gravitd de la Figure. (Essai d'une nouvelle Théorie de la résistance des fluides.)
page 193 note ‡ It appears doubtful if, in 1889—nearly another century later—Lilienthal was not ignorant of this ; though Colonel Duchemin in 1842 had "gone into the question very fully.
page 203 note * Da ciò segue di necessaria consequenza che il centro di resistenza mcontrata da un piano e sottil corpo rettangolare moventesi per Facqna o per l'aria tranquilla sotto un qualunque angolo acuto colla direzione del suo movimento, sarà tanto meno distante dal centro di grandezza delta superfcie anteriore del solido, quanto pin grande sarà la sna velocita.
page 206 note * Pei ragionamenti del § precedente ei manifesta che il centre di resistenza incontrata da un piano e sottil corpo rettangolare moventesi per l'acqua, e per l'ariatranquillasotto un qualunque angolo acuto sarà tanto meno distante dal centro di grandezza della superficie anteriore del solido, quanto piú sara grande il lato longitudinale della superficie medesima.
page 206 note † From what was said about the second law, the reader will easily see that the correct explanation is that increasing the length of the plate produces the mmc effect on the vortex at the rear of the lamina, as increasing the velocity. There appears to be no reason for supposing that the position of the “divide” is altered.
page 208 note * It will bo evident that, in this case, increasing the breadth of the plate tends, sensibly (though slightly) to shift the centre of the vortex behind the lamina, from o 1 towards l 1; after which it again returns to o 1. The rotation, in this case, beiag counter-clockwise in Fig. 6.
page 210 note * Whether Avanzini ever proposed this formula, or not, I am unable to say. I have never seen the paper, nor have I ever come across anybody who had; but in any case it does not agree with the results of the experiments which he undoubtedly published and which I have seen and studied.