198 
DR. BREWSTER ON REFLECTED LIGHT. 
Image at the 
Names of Oils. Image at the Surface of Prism A. Surface of Prism B. 
fAt a low temperature the orders are scarcely perceptible,*] 
n;i J the second limit only being visible. Heat brings out „ 
Oil of Marjoram . . (he second limil at a i ess in “ itlence> and creates th “ fir8t f Whitish yellow. 
(, limit at 79°. 
Castor Oil See page 193. 
Oil of Hyssop •••• { C °Fi!£t2^7°. He “ bringS ° U * ,hree S ood ordcrs - } Whitish yellow. 
Oil of Fenugreek.. / Colo “' s , rather , bett f than the preceding. Heat brings 1 whltisl 1Iow . 
° (_ out three good orders. First limit at 75 . J J 
Oil of Caraway-seeds Two orders, not good. Whitish yellow. 
Oil of Thyme .... Slight tinges of colour. Heat brings out two good orders. Yellowish white. 
Oil of Turpentine . Two tolerably good orders. First limit at 74°. Whitish yellow. 
Cajeput Oil | Two tolerably good orders. First red bad, second red 'j Yellowish white 
T - , f Two extremely faint orders. Three good orders brought ~| -.r „ . , , . 
Lll,seedC)l1 t out by heat. First limit at 73°. ] Yellowish white. 
rp. • , f Three very good orders. First red and first blue excel- 1 n , . , , . 
TrainGl1 1 lent. First limit at 73°. Heat spoils the first order. } Yellowish white. 
f Almost no colours, both images being yellowish, and that") 
Oil of Savine . . . . < of B brightest. Heat brings out three orders. First ^-Yellowish white. 
L limit at 80°, which a greater heat brings to 75°. J 
f Almost no colours. A sort of bluish gray when cold."] 
Heat brings out two good orders when temp, only 90°, ^-Yellowish white, 
but greater heat injures them. 
Oil of Pennyroyal 
Oil of Almonds 
Three tolerable orders. First red bad, second red good. Yellowish white. 
f Gives three and a quarter orders when cold. First limit at"] 
about 80°. 
Oil of Mace <( When the film of the oil begins to crystallize, it displays V Pretty bright. 
red, blue, and greenish tints, at the same incidence, in | 
(_ different places. J 
J Very faint colours. Heat brings out three good orders.^ Yellowish at great 
incidences. 
Oil of Spearmint . . j F j rs , ^ „ ab ' out „o 
Oil of Lemons . 
J 
f Three fine orders. First limit at 74°. Heat destroys the! Y e ll ow ish white 
\ first order. / 
Oil of Dill Seed 
JTwo poor orders of colours. First limit at 73° 
\ improves them. 
Heat 
1 
Yellowish white. 
Oil of Peppermint . { Tw fi ° rs t ^ ^ ^ ^ deStl ° yS ^ } Yellowish white - 
OilofRapeseed .. { Tv ' b ° ^ faint orders> Hmit at 65° when improved j B i uis h gray. 
Naphtha from Persia Three very good orders. 
White. 
