METHOD OF EXAMINING DISPERSIVE POWERS, 



93 



of refractive power in a cryftalline lens of an ox, afcertained by 

 trial, but alfo an average, computed from the refractive denfity 

 of a dried cryftalline of an ox, of which the weight had been 

 firft taken in the recent ftate, and the .quantity of water loft by 

 drying alfo meafured. 



The table exhibits a feries of fubftances, arranged according Table of refrac- 

 to their refractive powers. That of the diamond h copied from tlve P owcrs * 

 Sir Ifaac Newton ; of other bodies to which (on account of 

 their being more denfe than glafs) the machine for meafurement 

 would not apply, the refractive powers have been found by 

 other means, for the fake of furnifhing a more continued feries 

 of fubjects for comparative experiments. The reft have been 

 compared by this method ; and their power, when exprefled in 

 numbers, actually meafured. 



TABLE I. 



Diamond - - 2,44 



Plumbago ■ r - — 

 Native fulphur (double) 2,04 

 Glafs, confifting of lead 



6 and fand 1 - 1,987 



Glafs of antimony * 1,98 



Jargon - - J, 95 



Spinelle ruby - 1,812 



Arfeoic - - 1,811 

 Muriate of antimony, variable 



White fapphire - 1,768 



Gum dragon - — 



Iceland fpar, ftrongeft 1,657 

 Sulphate of barytes 



(double) - - 1,646 



BalfamofTolu - 1,60 



Guaiacum - - 1,596 



Benzoin - — 



Flint glafs - - 1,586 



Ditto - - - 1,583 



Horn — 



Phofphorus - - 1,579 



Mica — 



Opium — 



Amber -" - 1,547 



Rock cryftal (double) 1,547 



Old plate glafs - 1,545 



Colophony - - 1,543 



Box-wood — 



Bees- wax - - 1,542 



Oil of faflkfras - 



Red fealing-wax 



Spermaceti, cold 



Sugar, after fufion 



Arfeniate of potafli 



Maftic 



Elemi 



White wax (cold) 



Oil of cloves 



Copal - 



Anime 



Radcliffe croxun glafs 



Pitch' 



Centre of cryftalline of 

 flfh, and dry cryftal- 

 line of an ox 



Canada balfam 



Crown glafi, common 



Selenite 



Caoutchouc 



Gum lac 



Dutch plate glafs 



Human cuticle 



Gum arabic 



Baliam of capivi 



Oil of amber 



Englifli plat e g lafs 



French plate glafs 



Oil of nutmeg 



Sulphate of potafh 



1,536 



1,535 

 1,535 

 1,535 

 1,533 



1,530 

 1,528 

 1,525 

 1,525 

 1,524 



1,517 



1,514 

 1,507 

 1,505 

 1,504 

 1,500 

 1,497 

 1,495 

 Tallow 



