V E G 



different mining diflrifts. Schiilus too, in whicfi there is 

 generally a great deal of iron and alum, is found fo unfa- 

 vourable to vegetation, that any confiderable quantity of 

 it would deilroy the fertihty of the richeft forts of land. 

 The noxious^ corroding, and weakening effefts of fuch fub- 

 ftances on the tender roots of vegetables being fuch in fome 

 cafes as to caufe thejr decay, diflblution, and deftruftion. 

 Frequent ftirring, or tlie expofure of new furfaces of land 

 to the aftioii of the air, and the ufe of lime, chalk, or 

 other difTolving matters, will, it is fuppofed, correA the in- 

 jurious quahties of this fubftance, and promote the vegeta- 

 tion and growth of plants and crops in fuch ftates or land. 

 The aftringent principle or acidity in peat is often fo great 

 and fo noxious to vegetation, that until any quality of that 

 nature which may exift be fubdued, though that fort of 

 land be a perfett mafs of vegetable matter, nothing but 

 heath and other fuch miferable plants are capable of grow- 

 ing in it. Vegetation is confequently in fuch cafes only to 

 be affifted by breaking the parts of the land well dovi-n, and 

 the application of earthy and other matters to it, fo as to 

 wholly deftroy its aftringent property, and in faft change its 

 nature. See Soil. 



It may be noticed too, that the vegetation or growth of 

 plants and crops is frequently much injured and impeded by 

 the various forts of vermin with which the earth as well as 

 the air abounds. Thofe which inhabit the earth, it has been 

 fuppofed, may be deftroyed and got quit of by the ufe of 

 falijie matters, lime, and other different fubftances, opera- 

 tions, and arts, as are feen under their feveral proper heads. 

 See Grub, Mole, Slug, Worm, Vermin, &c. alfo 

 Turnip. 



But in regard to the myriads of thofe of the infeft kind 

 with which the air abounds, it is more difficult and uncertain 

 to propofe or point out any remedy or means of prevention 

 that may be effeftual. It is not afcertained that the fmell 

 of any plant, in its natural growing ftate, is deflruftive of 

 infefts ; but there are feveral plants which aie, when dried 

 and reduced to powder, or when burnt near to certain 

 infedls, deftruftive of them, as thofe of tobacco, hem- 

 lock, henbane, rue, wormwood, and others. Sometimes, 

 however, vermin of this fort are occafioned by the weaknefs 

 and unhealthy growth of the plants, and the poverty of the 

 foil of the land where they grow ; the beft remedies in fuch 

 cafes are, of courfe, thofe of more perfeft tillage and cul- 

 tivation, fo as to render them flrong and healthy in their 

 vegetation. 



Vegetation, ylrtificial. Many of the procefTes and 

 operations in chemiftry afford produftions, whether of falls 

 or metals, or of whatever other fubftances, which very 

 much refemble plants of one kind or other, whence they 

 have been called metallic vegetation. But though manv 

 have been hence induced to believe, that thefe produc- 

 tions were formed in the manner of vegetables, there is 

 not the leaft ground for fuch an opinion from reafon or 

 experiment. 



M. Homberg, who has treated very accurately of the 

 feveral kinds of thefe chemical vegetations, divides them into 

 three different claffes. 



Thofe of the firft ciafs are fuch as confift of a pure maffy 

 metal, without the mixture of any foreign matter whatever. 

 Thofe of the fecond clafs are compofed of a diftolved metal, 

 which, though it has concreted afterwards, yet retains a part 

 of the menftruum in it ; and the third clals contains thofe 

 which have no metal in them, but are merely compofed of 

 falts, oils, or earths, or of combinations of thefe. 



All the produftions of the firft kind are made without 

 the admixture of any liquor, and are merely owing to the 



V E G 



force of fire. Thefe are of a firm and folid texture, and 

 may be taken out of the veffels in which they were made, 

 without danger of breaking them. On the other hand, the 

 vegetations of the fecond kind are all formed in a fluid, and 

 are all fo brittle, that they are not to be touched without 

 breaking. Of the third kind, fome are formed, or will fub- 

 fift at leaft, in the dry air ; others are very tender, and are 

 formed only in fluids, the very ftirring about of which 

 deftroys them. See Arbor. 



Vegetation of Salts, a name given by M. Petit of the 

 Academy of Paris, to the concretions which falts form, after 

 folution in water, when fet in the air to evaporate. 



Thefe concretions always appear round the furface of the 

 liquor, affixed to the lldes of the vtffel, or arifing above its 

 top, and are very different in the different falts, and in moft 

 of tiiem very bL-autiful. 



One of the moft ready and molt beautiful of all the fahne 

 vegetations, is that formed by a folution of the falts in the 

 caput mortuum of aquafortis with common water. If a 

 pint of water be put,to half a pound of this caput mortuum, 

 and the whole boiled together, that the falts may be dif- 

 folved, and the liquor afterwards filtrated, and expofed in an 

 earthen veffel, there will be formed, in about eight and forty 

 hours, vegetations whollv hke thofe from the mixture of 

 fpirit of nitre and oil of tar, except that thofe from the caput 

 mortuum are more ramified and more beautiful. When the 

 folution is expofed in a glafs veffel, they form themfelves on 

 the furface into very beautiful figures of trees, fhrubs, and 

 bufhes ; and this not onlv on the furface, but on both the 

 infide and outlide of tlie glafs. Thefe can be compared to 

 no known concretion, except to the vegetations of iron, 

 defcribed by M. Lemerv ; they differ indeed in nothing 

 from thefe, but that the vegetations of the metal are of a 

 brownilh colour, whereas thofe of the fait are white. 



This impregnation fucceeds beft in dry weather, for in a 

 moift feafon the vegetations form themfelves more flowly, 

 and are much lefs beautiful. Glafs veffels are alfo eflential 

 to the vegetations being formed in their greateft beauty ; 

 they are never nearly fo beautiful in earthen ones ; and 

 even in the former, the vegetations fucceed much better in 

 fome fort of glafs than in others. The caput mortuum of 

 aquafortis alfo is very different, from the different dif- 

 tiUations ; and all of it does not fucceed alike in this vegeta- 

 tion of the fait. That which looks Hghteft, and of the 

 reddeft colour, feems the beft for this purpofe. An im- 

 pregnation of this caput mortuum in red-wine produces no 

 vegetations, but only forms a cruft with fmall eminences on 

 the fides of the veffel; and faltpetre, difTolved in the im- 

 pregnation of this caput mortuum in water, produces a 

 much more beautiful vegetation than that of faltpetre 

 alone ; but at the fame time much lefs beautiful than that 

 of the impregnation alone. Salt-water, difTolved in the fame 

 impregnation, fometimes will produce beautiful vegetations, 

 but fometimes only a rough cruft. Com.mon rough falt- 

 petre forms no vegetations, but .only cruils over the veffel ; 

 as is the cafe with the folutions of many of the metals in dif- 

 ferent acid menftruums. And the fame is the cafe in regard 

 to many falts from which it might be natural to expeft con- 

 cretions of this kind. Memoirs Acad. Par. 1722. 



VEGETIUS, Flavius Renatus, in Biography, hved 

 in the reign of the emperor Valentinian, to whom he dedicated 

 his treatife " De Re Mihtari." Although he was pro- 

 bably a mihtary man, his Latin ftyle was pure, confidering 

 the age in which he lived. The beft editions of his work 

 are the Variorum, Leyd. 1644, and Vefal. 1670. Tiirpin's 

 Commentary was printed in French, Paris 1783, in 2 vols. 

 4to. ( 



A wor.k. 



