VOL. XLV.j PHILOSOPHICAL TRANSACTIOXS. 537. 



with them. It was by the knowledge of the various weights of gold and silver, 

 that Archimedes is recorded to have detected the noted fraud committed in Hiero's 

 cro^vn, as Vitruvius has at large related in his Architecture, 1. ix, c. 13; and it 

 is from the same great philosopher that we have derived the demonstration of 

 those hydrostatical rules, by which the proportions are best to be known, of the 

 several weights or densities of different bodies, having the same bulk or magni- 

 tude: as may be seen in his tract De Insidentibus Humido, lost in the Greek 

 original, but retrieved in great measure, as it is said, from an Arabic translation. 

 It was published in Latin, with a commentary by Frederic Commandine, at Bo- 

 nonia 1565, 4to, and the substance of it by Dr. Barrow in his Archimedes, 

 printed likewise in 4to, at London 167 5. 



Pliny, in the 18th book of his Natural History, has set down the proportional 

 weights of some sorts of grain, among which he says that barley is the lightest. 

 And the same author, in his 33d book, speaking of quicksilver, observes that 

 it is the heaviest of all substances, gold only excepted. Which Vitruvius had 

 also taken notice of, and had mentioned besides the weight of a known measure 

 of it, that of 4 Roman sextarii. 



Again, Q. Rhemnius Fannius Palaemon, in his fragment De Ponderibus et 

 Mensuris, has given an observation, of the proportional gravities of water, oil, 

 and honey; stating that the sextarius of either water or wine weighed 20 oz. 

 the same measure of oil 18, and of honey 30. Their specific weights were 

 therefore in proportion as 1.0, O.Q, and 1.5, exactly agreeable to what Villalpandus 

 determined about the beginning of the last century; yet was this author himself 

 sensible that these were not to be considered as very nice experiments. After 

 which he proceeds to describe a pretty good instrument for readily finding the 

 different specific gravities of fluids; and shows how those of solids also may be 

 hydrostatically discovered. 



Francis Bacon, Lord Verulaixi, &c. in his Historia Densi et Rari, has given a 

 table, which he calls, Tabula Coitionis et Expansionis Materiae per Spatia in Tan- 

 gibilibus (quae scilicet dotantur pondere) cum Supputatione Rationum in Corpo- 

 ribus Diversis. This tract does not appear to have been published till after his 

 death, which happened in the year 1626, but was probably written several years 

 before , and the experiments were, as he tells us, even made long before that. Hanc 

 tabulam multis abhinc annis confeci, atque ut memini, bona usus diligentia. It 

 is probably therefore the oldest table of specific gravities now extant. The ex - 

 periments there mentioned were not made hydrostatically, but with a cube of an 

 ounce weight of pure gold, as he says, to which he caused cubes of other mate- 

 rials to be made equal in size: as he did also two hollow ones of silver, and of 

 equal weights, the one to be weighed empty, and the other filled with such liquid 

 as he wanted to examine. He was himself sensible that hLs experiments of this 



VOL. IX. 3 Z 



