Vifton. — Military Worhs.—Inflrununts. 8g 



ipreflure Is greatefl; and that, contrary to the obfervablc motion in a wheel, the part$ 

 neareft the axis in the prefent cafe move the fwifteft *. 



XI. On vlfion. — ^The invcrfion of images formed in the darkened chamber by rays ad- 

 mitted through a fmali hole in a plate of metal are explained by a diagram, and applied 

 to the phenomena of vifion. It is alfo remarked, that the apparent magnitude of remote 

 obje£ts may be enlarged by rendering the pencils of light more convergent. This is 

 iliewn by a figure, but the means are not pcrfpicuoufly explained. 



XII. On military architeiTlure. — Under this title the author gives diredlions for con^ 

 ftru£Ving military works ; and confiders their relative properties with regard to attack and 

 defence. He exhibits, as his commentator remarks, a fketch nearly complete of the art 

 of fortification, and, the attack and defence of places, at the commencement of the fix- 

 teenth century. We obferve platforms, buttrefies or counterforts, ravelins, the glacis 

 furrounding the ditch, trenches, advantages of the ricochet, mines and countermines, and 

 in fome defigns of de Vinci there are even counterguards. It muft however be remarked, 

 that Leonardo was much fuperior to tlie engineers of his time ; in proof of which his ob- 

 fervations in this feflion may be compared with what Machiavel delivers on the fame 

 fubjedt in his Art of War, and what Albert Durer has written upon fortification f. 



It is pretended that the baftions of Verona % were the firft which were conftrufted with 

 right-lined faces, fianked in the modern fafliion ; and the merit of this invention has been 

 afcribed to San Michel. The baftions of Verona were however conftruded after the death 

 of Leonardo, who had explained the necelTity of that difpofition, and has marked embrafures 

 in each flank of the baftion in one of his figures. 



Geufs, in his Theorie de PArt du Minetir ||, reproaches Valliere for having robbed Peter 

 Navarro of the glory of the invention of mines, to attribute it without foundation to 

 Francis G eorgi §. Valliere may be defended by the tefl;imony of Biringuccio, who was the 

 countryman and contemporary of Georgi. He exprcfsly fays H, " that it was this en- 

 gineer who, being confulted by Navarro refpe£ting the means of taking the caftle of 

 Naples, propofed and executed the mines, and that the glory remained with the com- 

 mander General Navarro, becaufe renown difpofes itfelf on the fide of great men." But, 

 in faft, the invention of mines with gun-powder is more ancient than either of thefe per- 

 fonages. The Genoefe executed them in 1487 **. The manufcript N" 7239 of the 

 French National Library was written by an Italian who lived at the commencement of 

 the 15th century. The author explains very clearly (fol. 32) the manner of taking a 

 caftle fituated on a mountain, by the operation of mines ff. 



XIII. Concerning certain inftruments. — i. The proportional compafles. Its centre is 

 moveable ; and, as the author remarks, it may be ufed for the proportions of incommen- 

 furable quantities, and alfo to form an oval which (hall have a given ratio to a given 



* ProfelTor Vcnturi has treated this fubjeft in his Recherches Experimemales, &c. p. 5R, for an account of 

 vvhich work fee our Journal, I. 525. 



f De urbibus arcibus caftellis, fol. Paris, 1535. % MafFei Iftocia di Verona, part. 3, cap. 4. 



jl In 8vo. Maftricht 1778. § 21. § Folard, torn. iii. 



^ Pyrotechnia, !iv. ip. cap. 4. •» Guieciardini Iftoria, lib. vi. i 



t+ Mr.Venturi gives a more particular account of this manufcript and its contents in the notices at the end 

 of the prefent treatife. 



Vol, TL— Mat 1798. N circle. 



