V.OL. XLV.] rHlLOSOPHICAL TRANSACTIONS. 53^ 



his death by Mr. Samuel Foster in 1626, having ocx;asion to mention the spe- 

 cific weights of the several fixed metals, quoted Ghetaldus, and made use of his 

 proportions, and so did also Mr. William Oughtred, in his Circles of Propor- 

 tion, first published in 4to, l633, with this only difference, as to the form, that 

 he changed Ghetaldus's unit into 210, by which he expressed all his relations in 

 whole numbers. It is likewise probable that D. Henrion took from the game 

 place the numbers he applied in his Usage du Compas de Proportion, printed at 

 Paris in l631, 8vo; though he has not given them all with exactness, for the 

 sake as it seems of using simpler vulgar fractions. 



Father Mersenne, a French minim, in his Cogitata Physico Mathematica, 

 printed at Paris in 1644, 4to, has given from the observations of his accurate 

 friend Petre Petit, a table of the specific gravities of the metals and some other 

 bodies, making gold 1 00, water 3-^, and the rest in proportion. These are here 

 reduced to the common form, and inserted under his name in the following 

 tables. The same were afterwards made use of by Father Francis Milliet de 

 Chales, Jesuit, in his Cursus Mathematicus, Mons. Ozanam, Professor Wol- 

 fius, and several others. Dr. D. has not seen Petit's own book, but it was enti- 

 titled L'Usage ou le Moyen de Pratiquer par une Regie toutes les Operations du 

 Compas de Proportion — augmentees des Tables de la Pesanteur et Grandeur des 

 Metaux, &c. had a privilege dated in l625, though it is said not to have been 

 printed till some years after. The same Father Mersenne has also taken notice, in 

 his general preface, of a table of 20 specific gravities, some time before published 

 by Mons. Aleaume, which he there sets down; but which he also observes are 

 very incorrect. Dr. D. has not therefore inserted any of them in this collection. 



Mr. Smethwick, one of the earliest members of the Royal Society, commu- 

 nicated to the same in July 1670, the weights of a cubic inch of several different 

 substances, said to have been formerly taken by Mr. Reynolds in the Tower of 

 London. This gentleman was the same who composed several tables relating to 

 the price of gold and silver, which were published in a book entitled the Secrets 

 of the Goldsmith's Art, at London, 1676, in 8vo. These weights are expressed 

 in decimals of an avoirdupois pound, are carried to 8 places of figures, and seem 

 to have been carefully and accurately collected. Dr. D. has therefore in the fol 

 lowing tables reduced them to the common form, in order to give them their 

 proper authority with the rest. He knows not whether these weights were ever 

 before printed or not, neither can he give any account, after what particular 

 manner the experiments were made, from which they were taken. They were 

 communicated to him from the register books of the Royal Society; and he 

 only observes, that the absolute weight here assigned of a cubic inch of common 

 water, does not differ more than a small fraction of a grain, from the weight, of 

 the same afterwards determined by Mr. Ward of Chester. ip 



