156 
GARDENING AS A SCIENCE. 
White pure Copal , the products are — Carbon . 
Oxygen and Hydrogen 
Hydrogen in excess 
76*81! 
12-052 
11-137 
100 
There are other resinous substances produced by plants of warm climates, whicli 
are highly fragrant, odorous, or foetid. They are partially soluble in water, and 
therefore have been termed Gum-resins ; — the fragrant balsam of tolu ; Gum Ben- 
zoin, frankincence, ammoniacum, assafoetida, olibanum, rank among these compounds 
14. Camphor. In noticing this singular substance, we must depart from th( 
authority of Davy, as recent discoveries refer it to the volatile or essential oils. 
15. Fixed Oils — or, for example, those of the olive, walnut, almond, beech-nut 
rape-seed, poppy- seed, mustard, sun-flower-seed, — kernels of plum, cacao (called 
cocoa) — from the Theobroma> the chocolate nut; laurel-berry, &c. &c., are nutritive 
substances, of great importance, not only in the arts, but in domestic economy 
and for the preparation of fine soaps. Olive Oil has been analysed by the tw( 
French chemists named before, and found to yield of Carbon 77*213 : Oxygeij 
9-427: Hydrogen 13-360. 
16. Volatile , or Essential Oils , approach to the quality of resins — they evapo 
rate by heat ; are soluble in alcohol ; which the fat or fixed oils are not ; — and arc 
very slightly soluble in water. A strong and peculiar odour characterises each o 
them ; they inflame very readily, and by combustion afford different proportions o 
the same elements, namely, water, carbonic acid, and charcoal. 
These oils are deposited in cells of the leaves and bark, and may be seen in tb 
leaves of the myrtle tribe, and particularly in those of the cinnamon leaves am 
bark: this fact presents a strong proof of the immediate connection which exist 
between the foliage and liber of trees. 
The essential oils are of great utility to man. Some are medicinal ; such ar 
the oils of peppermint, spearmint, carraway, cloves, cinnamon, cassia, aniseed. a! 
perfumes, we are indebted entirely to the oils of lavender, orange blossom ( neroli ) 
lemons, bergamot, and rhodium. Yet, perhaps the most important of the essentia; 
oils is the Oil or Spirit of Turpentine , termed also Camphogen , or Camphine 
From this material we now possess the means of obtaining a light so pure an 
brilliant, that imagination can scarcely conceive a thing more beautiful ; yet it i 
attended with considerable danger. Turpentine yields a dense vapour , which tb 
chemist Dumas supposes to consist of 500 volumes of carbon vapour, and 800 c 
hydrogen, condensed into 100 volumes. 
Camphor , the product of Taurus Camphora , is supposed by Dumas to be a: 
oxide of an hydro-carbon, identical in composition with pure oil of turpentine 
Hence, the addition of oxygen only, is thought necessary to convert turpentine tjj 
camphor, and by analysis we find 100 parts of camphor to produce. 
Or, to Dr. Ure . 
According to Dumas — Carbon . . 79-28 
Hydrogen . 10*36 
Oxygen . . 10'36 
78-02 
11-58 
10-40 
