;So4. Revieiv of Hints to AgncuUunJt:. '215 



cluHon ; a conclufion, indcej, which has been verified by a thoufanJ 

 arguments, and afcertained by a thoufand cxpenmcitts, and wljich a- 

 niounts, in plain language, to nothing more than this — that earth, de- 

 prived of air, water, and elementary lire, commonly called heat, will 

 not produce vegtftation. 



< We may then, 1 think, take for granted this pofition, that vegita- 

 tion is producvd by air, water and fire, operating, in fon\c way or o- 

 thcr, mediately or immediately, on the earth • ! ' 



The water, the fire, and the air, for the part of the vegetable 

 {landing above ground, he obfervcs, are funiilhcd to our hand ; 

 but to get air adminillered to the feeds fown, or roots growing 

 inider grotuul — kk labor^ hoc opus ejh The fpecics of air required 

 for vegetation, he obferves (p. 12.), has beeii variouily defigned, 

 * but is now moil commonly known by the appellation o{ fixed 

 air, and, more philofophically, by that of carbonic acid. In tlik 

 confifts all, or nearly all, the doctrine of manures and the myf- 

 tery of vegetation. ' * As to the mode of obtaining and applying 

 tliis carbonic acid (pages 14. 15.), he modelUy declines averting 

 pofitively, * that it is produced by fermentation alone : ' he thinks, 

 however, he may pofitively afiert, * that it is generated by fer- 

 mentation ; ' and is convinced hiuifelf (which undoubtedly is moil 

 important information), and willies to imprefs it upon his agri- 

 cultural neighbours (which is highly charitable), * that in what- 

 ever proportion any fpecies of manure will produce fermentation 

 in the earth to which it is applied, in the fame, or (obferve the 

 modeity with which the vi6lorious conclufion is pullied) nearly 

 the fame proportion, it will, generally fpeaking (dill modeilly 

 cautious) produce vegetation. ' 



O 4 According, 



* That this air, applied to vegetables above ground, is highly con- 

 ■ducive to vegetation, has been afcertained by experiment. The elec- 

 trification of plants has, in like manner, been found alfo favourable to 

 their growth. Our author, however, (and indeed all theoriflsss aiming; 

 at extreme fimphcity of fyllem), ought to be reminded, that a prin- 

 ciple, found pow^erfully productive of a given operation, in its fimple 

 uncompounded flate, may be pfoduftive of very different effects, when 

 adminillered in a ftate of compofition with other principles. Though 

 fixed air, applied to growing vegetables, and inhaled by the abforbent 

 vefTels of the leaves, promotes their growth, it by no means follows of 

 courfe, that it would produce the fame effeiSl when combined with lime 

 or other alkalis. Though a fiery fliower, adminiftere<l from a watering; 

 pan in the hand of the gardener. Handing upon an infulatii;g ftool, and 

 highly eleclrified, is found extremely conducive to vegetation, it by no 

 means follows that the watering-pan, the proximate caufe, cut in pieces 

 — or the glafs globe of the eledlrical machine, the remote caufe, when 

 comminuted to powder — would cith>?r .of them coiiftitutc an efiicicnt 

 Tnanure. 



