VOL. XLV.] PHILOSOPHICAL TRANSACTIONS. 341 



thought might be of service, he has here subjoined to the others in the following 

 collection, having also made an alteration in the form, the better to fit it for ge- 

 neral use, by omitting the absolute weights of the several bodies in summer and 

 winter, and placing instead of them, after the name of each body, a decimal 

 number, expressing the proportion of its weight in winter to its weight in sum- 

 mer, supposed to be every where represented by unity. 



Sir Isaac Newton, in his Optics, printed in 4to at London 1704, gave a table 

 of the specific gravities of several diaphanous bodies. The experiments were 

 made by him with a view chiefly to optical inquiries, and to enable him to com- 

 pare their densities with their several refractive powers, we may therefore be well 

 assured that they were made by the great author with the most scrupulous care 

 and exactness. The table consists of 22 articles. 



John Harris, d. d. in his Lexicon Technicum, first printed at London in 

 1704, fol. republished at large the several tables of specific gravities of the Ox- 

 ford Society and L C. from the Philosophical Transactions, and that of Mr. Boyle 

 from his Medicina Hydrostatica, to which last he also added some experiments of 

 his own, made as it seems with good accuracy. These are here extracted, and 

 placed under his name in the following tables. 



Mr. John Ward of Chester, in his Young Mathematician's Guide, first printed 

 it seems in 1706, acquaints us, that he had himself for his own satisfaction, 

 made several experiments on the different specific gravities of various bodies ; and 

 that he was of opinion, that he had obtained the proportion of the weight that 

 one body bears to another of the same bulk and magnitude, as nicely as the na- 

 ture of such matter, as might be contracted or brought into a less body, viz. 

 either by drying, hammering, or otherwise, would admit of. And he has ac- 

 cordingly given, in the said book, the weight of a cubic inch of 24 different 

 substances, both in Troy and Avoirdupois ounces and decimal parts of an ounce; 

 which he further assures us required more charge, care, and trouble, to find out 

 nicely, than he was at first aware of. This table appears to have been well-es- 

 teemed, and to have had the sanction of Mr. Cotes's approbation, by his taking 

 it, when reduced to the common form, into that collection, which he drew up 

 for his own hydrostatical lectures. 



Roger Cotes, m. a. and Plumian professor of astronomy and experimental phi- 

 losophy at Cambridge, first giving about the year 1 707 a course of hydrostatical 

 and pneumatical experiments, in conjunction with Mr. Whiston in that univer- 

 sity, drew up, for the use of that course, a very accurate table of specific gra- 

 vitigs, collecting from several places such experiments as he took to be most ex- 

 act, and the best to be depended on. And as the judgment of so great a man 

 cannot but give a general reputation to such experiments as he had so selected. 

 Dr. D. in the following tables, distinguishes all such by the addition of the letter 



