S7o 
Dr. Wollaston’s Method of examining 
The table exhibits a series of substances, arranged according 
to their refractive powers. That of the diamond is copied from 
Sir Isaac Newton; of other bodies to which (on account of 
their being more dense than glass) the machine for measurement 
would not apply, the refractive powers have been found by 
other means, for the sake of furnishing a more continued series 
of subjects for comparative experiments. The rest have been 
compared by this method ; and their power, when expressed in 
numbers, actually measured. 
Table I. 
Diamond - - 2,44 
Plumbago - 
Native sulphur (double) 2,04 
Glass, consisting of lead 
6 and sand 1 
1.987 
Glass of antimony 
1,98 
Jargon 
1.95 
Spinelle ruby 
1,812 
Arsenic 
1,811 
Muriate of antimony, variable 
White sapphire 
1,768 
Gum dragon 
Iceland spar, strongest 
Sulphate of barytes 
1,657 
(double) 
1,646 
Balsam of Tolu 
1,6.0 
Guaiacum 
1*596 
Benzoin 
• — 
Flint glass 
1,586 
Ditto 
1.583 
Horn 
— 
Phosphorus 
1.579 
Mica 
- — 
Opium 
■ — 
Amber 
1.547 
Rock crystal (double) 
1.547 
Old plate glass 
1.545 
Colophony 
1.543 
Box-wood 
— 
Bees-wax 
1 ,54$ 
Oil of sassafras 
*>536 
Red sealing-wax 
— 
Spermaceti, cold 
■ — 
Sugar, after fusion 
— 
Arseniate of potash 
— 
Mastic 
— 
Elemi 
— 
White wax (cold) 
— 
Oil of cloves 
i *535 
Copal 
1*535 
