ao» SCIENCE OF A GRICULTUKE. Part II. 



I ( M i Kxnosod from tli-' i'i i i i / - in-- nv of tret-« ami of .linnet > « 1 1 vegetables. It is Insoluble in water, 



I I .7. B abtmlnad flram the Junfperui communis, but soluble in sleohol. When treated sith oxymtuiellc acid, 



lation, n .isMiiii,-, th«- coUnu of a withered leaf, and exhibits the re- 



i i •->. Blemt Is extracted flram the Imyriaeli itinera, rinoui pnopertiei mure diatinctly, 



I i.vi. Tit.i>itt*i. Is the produce of the PajnWu octahdra and 1467* Copei It (he produce of the /thus copallinum, a tret 



Kpului bsliamnata, which i- bond in Nonh America* 



is-. n. LabdeMoRi la obtained flram the Gutns eiwtlaus, 1468, An im f t w obtained from the HymervtVj Courbarit, or 



l |ii I . i>i»jHjU,imni>t t vrbthm qfGik oil, which hai becnaomnch Kk-u^i live, a natlTe of North America, 



lamed for lta medical vlrtaea»b the produce of th Bi 1469, /„, la the prodnoa of {be Aleuzites lacclfera, a native 



dron cilead -mm', a ahrub wbicheTowa in Judoo and hi Arabia, of the K.vst [ndii s. 



hut it la ao much rained ei the Inrfcs that lta Importation is pro. 1470, Bloom. I 'pun the epidermis of the leaves and fruit of 



hil.ited. Thi> ll the li.iim of tiiV.ul so much celebrated in certain specie, of plants, there is to lie found a tine, soft, and 



Scripture. I'lim eftyi it WSJ tir.t drought to Koine DJ the glaucous powder. It la p.trti. ularh observable upon cabbage 



ganj nil of Verpawtn It ii obtained in a liquid late flram In- leaves, ana upon plums, to which it ■ oinmunicatei a peeu- 



ebaooa made In the bark, andiaeoi ehal bluer to the tastes llax shade. It is known to gardeners by the name of bloom. 



1462. Co|i in -i, er Uilsi'ii ,j copm'M li obtained Aram the t'o- It is easily rubbed oil" by the finders ; and when viewed un- 



p hi r.i officinalis, der the microscope seems to he coml»osed of small opaque 



ltragan's blood U obtained from the Dractt'na draco, and unpolished granules, si.ine.ih.it sin. il.tr to the powder of 



Plerocarpus draco, and r'.tlainus /. star, h ; hut w ith ahigh magnifying powerit appears transparent. 



1464. Oianae la the produce of the d male. When ruM.ed oil, it is again reproduced* though slowly. It 



1165. /ti./i i ; /;ii/ raria, the produoeofthe i fptusrednf- raalabi the action of dews and tains, and is consequently inso- 



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



about llotanv It. is. which circumstance it has been suspected, with some pro- 



I li.ii. Bran ruin constitutes the colouring matter of the leaves bability, to be a resin. 



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

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

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

 and tar. 



1 174 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 hctu een 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, they 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. Galbatwm, obtained from the stem of the ftubon gal- 1481. Myrrh, the plant yielding which grows in Abyssinia 



I. .nuiii. and Arabia. Kruce says it belongs to trie genus Mimosa ; 



1474. ytmmi'iuVic, brought from Africa, in the form of smalt 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 emp'oyed in 



1 175. Scammom/, the produce of the Convolvulus Scammonia. medicine, ;.nd is esteemed an excellent stomachic. 



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



1477- F.uphorbium, the produce of the Buphorbu officinalis. strong and fetid smell, is obtained from tl»e Ferula assafce'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 cleaned, and the extremity cut off; a milky juice 



1478. Oltbanum is obtained from the Bosweah'u serriita, which exuo.es, 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 assafectida. 



si /e of a chestnut. It is brought to Europe in small agglutinated grains of dif- 



1 17'J. Sjgapenum is supposed to be obtained from the Feru^i ferent colours, white, red, yellow. It Ls hard, hut brittle. Its 



persica. taste is bitter, and its smell insufferably fetid ; the Indians 



I I si i. Gamboge, or gumgutt, the produce of the Garcinni use it as a seasoning for their food, and c II it the food of 

 Cambodia. the gods. In Europe, it is used in medicine as an antispas- 

 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. 



list. Bouofn is the produce of the Styrax Renzbin. 14S7. Balsam of tolu is obtained from the Tolutfera Eilsa- 



1 Is.'.. Stora t is obtained from the Styrax officinale. mum. 



I486. Styrax i, a semi-fluid juice, the produce of a tree said 14SS. Balsam nf Peru is obtained from the Mvrospermum 



to he cultivates:! in Arabia. peruiferum. 



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

 the /.at'irus 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 0DS87. AN hen 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. 1'ourcroy thinks it is merely the effect of the affinities 

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

 /.afirus 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 nf 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 Cuhuchu, a tree indigenous to South 

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

 indica and el.istica, Artocarpus integriiolia, and I'rceola elastica. Il '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 



