293 SCIENCE OF AGRICULTURE. Part II. 



1456. Mastich is extracted from the Plst^la Z/entfscus. of trees and of almost all vegetables. It is Insoluble in water, 



1457. Sandarach is obtained from the Junfperus commiinls, but soluble in alcohol. When treated with oxvmuriatic acid, 

 by spontaneous exudation. it assumes the colour of a withered leaf, and exhibits the re- 



1458. Elemi is extracted from the ^m^ris elemffera. sinous properties more distinctly. 



1459. Tacambac is the produce of the Fagara octdndra and 1467. Coptd is the produce of the /ihiis copallinum, a tree 

 PcSpulus balsamffera. which is found in North America. 



1460. Lahdanum is obtained from the Cfstus crdticus. 1468. Animif, is obtained from the Hymenal Cottrbaril, or 



1461. 0^)o6a/rtium,or6a/mo/Gi7eaf7, which has beenso much locust tree, a native of North /\merica. 



famed for its medical virtues, is the produce of the Balsamoden- 1469. Lac is the produce of the A leurites laccffera, a native 



dron gilead^nse, a shrub which grows in Judea and in Arabia; of the East Indies. 



but it is so much valued by the Turks that its importation is pro- 1470. Bloom. Upon the epidermis of the leaves and fruit of 



hibited. This is the balm of Gilead so much celebrated in certain species of plants, there is to be found a fine, soft, and 



Scripture. Pliny says it was first brought to Rome by the glaucous powder. It is particularly observable upon cabbage 



generals of Vespasian. It is obtained in a liquid state from in- leaves, and upon plums, to whichit communicates a pecu- 



eisions made in the bark, and is somewhat bitter to the taste. liar shade. It is known to gardeners by the name of bloom. 



1462. Copaiva,or balsam of copaiva is obtained from the Co- It is easily rubbed off by the fingers; and when viewed un- 

 palfera officinalis. der the microscope seems to be composed of small opaque 



1463. Dragon's blood is obtained from the Dracae'na rfr^co, and unpolished granules, somewhat similar to the powder of 

 Pterocirpus draco, and Calamus Rbtang. starch ; Dut with a high magnifying power it appears transparent. 



1464. Guaiac is the produce of the Gua/'aeum officinMe. When rubbed off, it is again reproduced, though slowly. It 



1465. Botany Bay resin, the produce of the Eucalyptus resinf- resists the action of dews and rains, and is consequently inso- 

 fera, a native of New Holland, and found in great abimdance luble in water ; but it is soluble in spirits of wine ; from 

 about Botany Bay. which circumstance it has been suspected, with some pro- 



1466. Green resin constitutes the colouring matter of the leaves hability, to be a resin. 



1471. The use of resins in the arts is very considerable ; but their medical virtues are not quite so great 

 as has been generally supposed. They are employed in the arts of painting, varnishing, embalming, and 

 perfumery ; and they furnish us with two of the most important of all materials to a naval power, pitch 

 and tar. 



1472. Gum-resins. This term is employed to denote a class of vegetable substances, which have been 

 regarded by chemists as consisting of gum and resin. They are generally contained in the proper vessels 

 of the plant, whether in the root, stem, branches, leaves, flowers, or fruit. But there is this remarkable 

 difference between resins and gum-resins, that the latter have never been known, like the former, to ex- 

 ude spontaneously from the plant. They are obtained by means of bruising the parts containing them, 

 and expressing the juice, which is always in the state of an emulsion, generally white, but sometimes of a 

 different colour ; or they are obtained by means of incisions from which the juice flows. This juice, which 

 is the proper juice of the plant, is then exposed to the action of the sun, by which, in warm climates, it is 

 condensed and inspissated, and converted into the gum-resin of commerce. Gum-resins, in their solid 

 state, are brittle, and less transparent than resins. They have generally a strong smell, which is some- 

 times alliaceous, and a bitter and nauseous taste. They are partially soluble both in water and in alcohol. 

 When heated, ihey do not melt like the resins, nor are they so combustible ; but they swell and soften 

 by heat, and at last burn away with a flame. By distillation they yield volatile oil, ammonia combined 

 with an acid, and have a bulky charcoal. The principal species of gum-resins which have been hitherto 

 applied to any useful purpose are : 



1473. Galbanum, obtained from the stem of the Bubon gal- 1481. Myrrh, the plant yielding which grows in Abyssinia 

 bknum. and Arabia. Bruce says it belongs to the genus Blimosa ; 



1474. Ammoniac, brought from Africa, In the form of small but however this may be, myrrh is the juice of the plant 

 tears; the plant which yields it is thought to be a species of concreted in the form of tears. Its colour is yellow, its odour 

 Ferula. strong but agreeable, and its taste bitter ; it is employed in 



1475. Scammony, the produce of the Convdlvulus Scamm6nia. medicine, and is esteemed an excellent stomachic. 



1476. Opoponax, obtained from the Pastinaca opdponax. 1482. Assafcetida, a substance which is well known for its 



1477. Euphorbium, the produce of the Buphdrlita officinalis. strong and fetid smell, is obtained from the Ferula assafoe'tida. 

 Its taste is caustic ; it is considered as a poison, but is occa- At four years old the plant is dug up by the root. The root 

 sionally employed in medicine. is then clpaned, and the extremity cut off; a milky juice 



1478. Oiiianum is obtained from the Bosw^liaserrkta, which exudes, which is collected; and when it ceases to flow an- 



frows in Arabia, particularly by the borders of the Red Sea. other portion is cut off, and more juice extricated. The pro- 



t is the frankincense of the ancients. It exudes from in- cess is continued till the root is exhausted. The juice which 



cisions made in the tree, and concretes into masses about the has been collected soon concretes, and constitutes assafoetida. 



size of a chestnut. It is brought to Europe in small agglutinated grains of dif- 



1479. Sagapenum is supposed to be obtained from the Ferula ferent colours, white, red, yellow. It is hard, but brittle. Its 

 p^rsica. taste is bitter, and its smell insufferably fetid ; the Indians 



1480. Gamboge, or gumgutt, the produce of the Garcfnia use it as a seasoning for their food, and call it the food of 

 Cambbgia. the gods. In Europe, it is used in medicine as an smtispas- 



modic. 



1483. Balsams. The substances known by the name of balsams are resins united to the benzoic acid. 

 They are obtained by means of incisions made in the bark, from which a viscous juice exudes, which is 

 afterwards inspissated by the action of the fire or air, or they are obtained by means of boiling the part 

 that contains them. They are thick and viscid juices, but become readily concrete. Their colour is brown 

 or red ; their smell aromatic when rubbed ; their taste acrid ; their specific gravity 1090. They are un- 

 alterable in the air after becoming concrete. They are insoluble in water, but boiling water abstracts part 

 of their acid ; they are soluble in the alkalies and nitric acid. When heated they melt and swell, evolv- 

 ing a white and odorous smoke. The principal of the balsams are the following : benzoin, storax, styrax, 

 balsam of tolu, and balsam of Peru. 



14S4. Benzoin is the produce of the St^ax Benzbin, 1487. Balsam of Mu is obtained from the Toluffera B^lsa- 



1485. Storax is obtained from the Storax officinale. mum. 



1486. Styrax is a semi-fluid jtiice, the produce of a tree sziid 1488. Balsam qf Peru is obtained from the Myrosp^rmum 

 to be cultivated in Arabia. , perutferum. 



1489. Camphor. The substance known by the name of camphor is obtained from the root and stem of 

 the Laurus Cumphora and Dryobalanops Camphora, by distillation. When pure it is a white brittle sub- 

 stance, forming octagonal crystals or square plates. Its taste is hot and acrid ; its odour strong but 

 aromatic ; its specific gravity 09887. When broken into small fragments and put into water, on the 

 surface of which it swims, a singular phenomenon ensues. The water surrounding the fragments is 

 immediately put into commotion, advancing and retiring in little waves, and attacking the fragments with 

 violence. The minuter fragments are driven backwards and forwards upon the surface as if impelled by 

 contrary winds. If a drop of oil is let fall on the surface of the water it produces an immediate calm. 

 This phenomenon has been attributed to electricity. Fourcroy thinks it is merely the effect of the affinities 

 of the camphor, water, and air, entering into combination. Though camphor is obtained chiefly from the 

 ia6rus Camphora, yet it is known to exist in a great many other plants, particularly labiate plants, and 

 has been extracted from the roots of zodoary, sassafras, thyme, rosemary, and lavender. 



1490. Caoutchouc. The substance denominated caoutchouc was first introduced into Europe about the 

 beginning of the eighteenth century ; but, from a use to which it is very generally applied of rubbing out 

 the marks made upon paper by a black-lead pencil, it is better known to most people in this country by 

 the name of Indian rubber. It is obtained chiefly from Siphbnia Cahuchu, a tree indigenous to South 

 America; but it has been obtained also from several trees which grow in the East Indies, such as Flcxis 

 indica and elastica, Artocarpus integrifMia, and Urcfeola elastica. If an incision is made into the bark of 

 any of these plants a milky juice exudes, which, when exposed to the air, concretes and forms caoutchouc. 

 As the object of the natives in collecting it had been originally to form it into vessels for their own use, it 

 is generally made to concrete in the form of bags or bottles. This is done by applying the juice, when 

 fluid, in thin layers to a mould of dry clay, and then leaving it to concrete in the sun or by the fire, A 

 second layer is added to the first, and others in succession, till the vessel acquires the thickness that is 

 wanted. The mould is then broken and the vessel fit for use, and in this state it is generally brought 



