538 PHILOSOPHICAL TBANSAGTIONS. [anNO 1748. 



sort were,, notwithstanding his care, very defective. From among these, not- 

 withstanding their imperfection, as they appear to have been some of the first 

 experiments of the sort regularly digested, and as they were besides made by so 

 great a man, Dr. D. has extracted the specific gravities of the fixed metals, which 

 he has inserted as examples in the following tables, after reducing them to the 

 common form, on the supposition that pure gold was, according to Ghetaldus, 

 just 19 times as heav}' as water. And this he rather chose to do, than to make 

 use of his Lordship's own weight of water given in the table, which in the man- 

 ner he took it could not be very exact, and which besides would not have brought 

 out the specific gravity of pure gold more than 1 8 times as much ; and that of 

 the other metals in proportion. This table contains in all 78 articles. 



There are also in the 3d volume of the folio edition of his works, p. 223, 

 Certain experiments made by the Lord Bacon about weight in air and water. 

 These are truly hydrostatical, but very imperfect, Dr. D. has not therefore in- 

 serted any of them in the following collection. 



Marinus Ghetaldus, a nobleman of Ragusa, published in 4to, at Rome, in 

 l603, his treatise entitled, Promotus Archimedes, seu de Variis Coiporum Gene- 

 ribus Gravitate et Magnitudine Comparatis, where he has given a comparison 

 between the specific gravities of water and eleven other different substances, from 

 his own hydrostatical experiments, made with care and exactness. These are 

 here inserted; expressing the numbers as they stand in his own book, but Dr. 

 D. has afterwards also for uniformity reduced them to the decimal form. He has 

 besides, at the end, transcribed at large the 2 tables of this author, in which 

 every one of the 12 sorts of bodies, he treats about, is successively compared 

 with all the others, both in weight and magnitude. 



Father Johannes Baptista Villalpandus, a Jesuit of Cordova in Spain, in his 

 Apparatus Urbis et Templi Hierosolymitani, printed in folio at Rome, in l604j 

 exhibited a table of the proportional weights of the 7 metals and some other 

 substances, from his own experiments, made with great care, as he tells us, by 

 the means of 6 equal solid cubes of the fixed metals, and a hollow cubical vessel 

 8 times as large, for the comparing mercury, honey, water, and oil with the 

 same. His numbers, which are inserted under his name in the following tables, 

 were also again published by Joh. Henr. Alsted, in his Encyclopaetlia Universa, 

 printed in 2 vol. in folio, at Herbom, l630, and by Henry Van Etten, in his 

 Mathematical Recreations, whence they have been often transcribed into other 

 books. Villalpandus's book, which is only the 3d volume of a work begun to be 

 published several years before, was itself printed so soon after Ghetaldus's, that 

 it is probable he either never saw that author, or not at least till after his own 

 experiments were made. 



Mr. Edmund Gunter, in his Description and Use of the Sector, printed after 



