[ 424 ] 
fame place the numbers he applied in his Ufage du 
Compas de Troportion , printed at Tarts in 1631, 
8°. although he has not given them all with exaft- 
nefs, for the fake as it feems of ufing fimpler vulgar 
fractions. 
Father Mar inns Merfennus , a French Minim, in his 
Cogitata Thy fico -Mathematic a, printed at Tar is in 
1 644 . 4 0 , has given from the obfervations of his ac- 
curate friend Tetrns.Tetitus , a table of the fpccific 
gravities of the metals and fome other bodies, making 
Gold 100, Water 5-J, and the reft in proportion. 
Thefe I have reduced to the common form, and 
inferted under his name in the following tables. The 
fame were afterwards made ufe of by Father Francis 
Milliet de C hales , Jefuit, in his Curftis Mathema- 
tics, Monfieur Ozanam, Profeffor Wolfius, and fe- 
veral others. I have not feen Tetitus ’ s own book, 
but it was entitled L Ufage on le moyen de pratiquer 
par une Regie toates les Operations du Compas de 
Troportion — augment ees des Tables de la Pesanteur 
et Grandeur de‘s Metaux &c. had a privilege dated 
in 1625. tho’ it is laid not to have been printed till 
fome years after. The fame Father Merfennus has 
alfo taken notice, in his general preface, of a table 
of 20 fpecific gravities, fome time before publifhed 
by Monf. Aleaume , which he there fets down, but 
which he alfo obferves to be very incorrect. I have 
not therefore inferted any of them in this collection. 
Mr. Smethwick, one of the carlieft members of 
the Royal Society, communicated to the fame in July 
i 670 the weights of a cubic inch of fevcral different 
1 ? fubftances > 
