^ Rotatioti of the Earth. — Proje^ihs, ^c. 



VIII. 



ExlraHs from the Manufcr'tpts if Leonard de Vinci. With Remarks, by J. B. V£NTVRi, 

 ', ' ProfeJJbr of Natural Philofophy at Modena, Member of the In/iiluie of Bologna *. 



I. V-/N the defcent of heavy bodies combined with the rotation of the earth, De Vinci 

 (hdws by a figure, that a body let fall from an emhience will continue perpendicularly over 

 the f.ime fpot, riotwithftanding the rotation of the earth, and confequently infer^ that 

 it will defcribe a fpii-al line. (It is an ellipfis.) 



It. was at the commencement of the j6th century that the works of Nicolas de Cufa 

 tpfete- printed, in which that author endeavoured to renew the ancient dodlrine of the 

 motion of the earth, though in a confufed and metaphyfical method. 1 he writing of de 

 Vinci is nearly of the year 1510, and fliows that this notion was in a ftate of difcuffion in 

 the minds of difcerning men before the time of Copernicus. It has been aflerted, that 

 Rcgiomontanus fupported this do£lrine j but he oppofes it direiSlly in a writing prcferved 

 by Schoner, and in his commentaries on the Almageft f. The doclrine of tlie motion of 

 the earth was publicly maintained for the firft time at Rome, in 1533, by Widmanftat|:, 

 who affirmed that he had learned it from Copernicus. The work of this lad did not 

 appear till 1543. Vinci was the only man at that time who was fufficiently acquainted 

 with mechanics to apply the theory of combined motion to the fall of heavy bodies, an 

 application of which Uie honour was afllimed by Gaflendi in the laft century§. In this 

 ftate the opinion of philofophers remained, until D'Alembert demonllrated, that heavy bo- 

 dies projcfled towards the zenith ought not to fall exaiSlly at the place wlience they ftt 

 omt. A fimilar idea has been taken up in my country. The .tower Afinelli in Bologna 

 is about three hundred feet high. A ball exaftly round being let fall from this height to 

 the earth, ought to deviate nearly fix lines from the perpendicular. J. B. GuUielmini made 

 the experiment in 1792 with great care. He could not avoid fome aberrations, of which 

 the mean refult, however, confirmed the truth of a izSt which had before been demon- 

 ftrated by aftronomy and mechanics ||. 



II. Concerning the earth divided into fragments. — L. de Vinci affirms, that if the earth 

 were curt into fragments, and difperfed through the furrounding fpace, a fingle fragment 

 being let fall would be carried to the common centre, which it would pafs to a nearly 

 equal diflance on the oppofite fide, and return again nearly to the place whence it fet out ; 

 and in this way the vibrations would continue : — that if all the fragments were fuftercd to 

 fall at different times, they would meet^ ftrike, and break each other, ,apd a tumultuous 



"* From the " Effhi fur les Ouvrages Phyfico-Mathcmatiques de Leonard dc Vinci, '' of which notice is taken 

 in Philof. Journal, I. 599'. 1 have abridged the palTageS in many inftances. All the remarks in the text are 

 by Proftdor Venturi. 



+ Schbii'eH Opera, pars fecunda, cart. 127. Rcgiomoutan. in Almageftum, 1. p. concluf. 5. 



J Marini Anchiatri Pontificii, torn. 2, pag. 351. 



§ De motu impreffo amotore tranflato. Paris 1642. 



H De diurno terrae motu expcrimentis confirmato. Bonon. 1792. — An experiment of this nature was propofej 

 to the Royal Society, and a difcourfe read thereon by Robert Hooke, who inferreii that the ball would in our 

 latitude fall to the S. E. This, on trial about December 1679, proved to be the cafe. See Ward's Lives of 

 the Greiham Prcfeffors, p. 184. N. 



:: ;>; commotion 



