540 PriltOSOPHICAL TRANSACTIONS. [aNNO 1748. 



The Philosophical Society, meeting at Oxford, directed several experiments to 

 be made hydrostatically by their members, concerning the specific gravities of 

 various bodies; which being digested into a table, were by Dr. Musgrave com- 

 municated to the Royal Society the 21st day of March l684; soon after which 

 they were printed in the l6gth number of the Philosophical Transactions. These 

 experiments were, according to Dr. Musgrave, made by Mr. Caswell and Mr. 

 Walker; they are all originals, and are esteemed some of the most accurate that 

 are extant. 



The Hon. Robert Boyle, at the end of his Medicina Hydrostatica, first pub- 

 lished at London in 1690, Svo, subjoined a table of the specific gravities of se- 

 veral bodies, accurately taken from his own hydrostatical experiments. Besides 

 which, there are also in the same tract, and in other parts of his works, several 

 experiments of this excellent author's, which he has given occasionally, with 

 the uses resulting from them. To such of these in the following collection, as 

 were taken from the table just mentioned, his name is annexed ; but to such of 

 the others as occurred. Dr. D. has also added the volume, page, and column, 

 of the late folio edition of his works in 1744, where the same are be be found. 

 It may be noted, that in the first edition of the Medicina Hydrostatica, there were 

 several errors of the press. Such of them as he could discover by calculation, he 

 has corrected in the following pages. 



There is a table published under the name of J. C. in the IQQth number of 

 the Philosophical Transactions, anno 1 693 : and this is evidently a supplement to 

 that abovementioned of the Philosophical Society meeting at Oxford. The expe- 

 riments were, according to the initials J. C. made by the same curious person 

 Mr. John Caswell, and are therefore of the same estimation as the others. 



M. Homberg, of the Royal Academy of Sciences at Paris, read a memoir in 

 1699, where he noticed the expansion of all substances by heat, and the con- 

 traction of the same by cold; whence it must follow, that the specific gravities 

 of the same bodies would constantly be found less in the summer and greater in 

 the winter. And this he showed fi-om the experiments he had made on several 

 fluids, both in the summer and the winter seasons, by means of an instrument 

 he had contrived and called an araeometer, being a large phial, to which he had 

 adjusted a k)ng and slender stem, by which he could well determine when it was 

 filled with equal bulks or quantities of the several fluids he proposed to examine. 

 The result of his trials with this instrument he digested into a short table, which 

 was printed in the memoirs of the Academy for the same year 1699. This table 

 John Caspar Eisenschmid afterwards republished, with several additions, in his 

 tract De Ponderibus et Mensuris, printed at Strasburg in 1 7O8, 8vo, changing 

 it to a more convenient form for his purpose, by reducing the different fluids to 

 the known bulk of a cubical Paris inch. So much of this table as Dr. D. 



