CAMPHOR. 345 
camphor, when viewed microscopically, was found to consist of 
masses of six-sided tabular crystals with a few six-sided prisms 
scattered amongst them. Their volatility was so marked that even 
while under the microscope they lost the sharpness of their angles 
and soon degenerated into ill-defined masses. He found the sp. 
gr. of the three sorts of camphor (after exposure in vacuo to remove 
interstitial and adherent air) to be as follows :— 
Laurel camphor . . . 0°995 
Ngai x3 Scop hae 
Borneo __,, si » Seed 
(Unless deprived of adherent air both the Borneo and Ngai 
camphors will swim on water and turn on it in the same way as 
common camphor.) 
The melting-point of each was found by introducing a small 
quantity into a thin narrow tube, sealing one extremity and im- 
mersing in melted paraffin, then gradually heating till the little 
column of camphor became transparent and noting the temperature 
of the surrounding paraftin; by so dcing the mean of the melting- 
and solidifying-points was found to be 177°C. for the laurel cam- 
phor, 204° C. for the Ngai, and 206° C. for the Borneo. 
The physical characters of the three varieties of camphor were 
subsequently studied by Professor Fliickiger *. He observed that 
crystals of common camphor appear in forms belonging to the 
hexagonal system, as previously shown by Des Cloiseaux +, and 
they exhibit in polarized light brilliant colours like other crystals 
not belonging to the cubic system. This is easily demonstrated by 
examining a clear splinter of ordinary camphor under the polari- 
zing microscope. or by melting a little camphor between two slips 
of glass and examining it in the same way. According to Des 
Cloiseaux ¢ the crystals of Borneo camphor derived from Dryo- 
banalops belong to the cubic system, an observation confirmed 
by Fliickiger, who adds that they display no action on polarized 
light when examined in the way above described; regular cubes 
and all allied forms being devoid of that optical power. Crystals 
of Ngai camphor examined by means of the polarizing microscope 
proved likewise to belong to the cubic system. 
* Pharm. Journ. [3] iv. p. 829. 
+ “Etudes du Camphre ordinaire,” Comptes Rendus, 1859, p. 1064, 
t Ibid. 1870, p. 1209, and Pogg. Annalen, 1870, p. 302. 
