130 Outlines of Horticultural Chemistry. 



We have seen that every plant has a particular tempera- 

 ture in which it thrives best; a particular modification of 

 food, a particular degree of moisture, a particular intensity of 

 light, and that these particularities vary again at different 

 periods of their growth. It is equally certain that they are 

 subject, like all other matter, to various influences (the appli- 

 cation of some substances corrodes them); nor are these uni- 

 form. Acids are injurious to some plants, alkalies to others, 

 &c. ; the excess of some of their constituents, and the deficiency 

 of others, insure disease to the plants in which such irregula- 

 rities occur ; disease is accompanied by decay, more or less 

 extensive and rapid, and ultimately death ensuing, each plant 

 is reduced into its proximate elements. Now, if it were pos- 

 sible for any science to teach the cultivator of plants, how to 

 provide for them all the favourable contingencies, all the ap- 

 propriate necessaries above alluded to, and to protect them 

 from all those which are noxious to them, the art of cultiva- 

 tion would be far advanced to perfection ; yet such a science 

 is chemistry. 



I do not mean to advance that chemistry, as at present 

 known, is capajole of supplying all the desiderata I have alluded 

 to, but it can many of them. Besides, chemistry has not 

 reached its present state in a day; it has been the work of 

 ages, and is daily improving ; neither has it been the creation 

 of one mind, but has been the gradual structure of many intel- 

 lectual labourers, from the days of the Arab alchemists until 

 now. Let it not then be supposed, that the cultivator of the 

 soil should wait for others to make discoveries, and that he 

 need only take advantage of them. Should the physician be 

 ignorant of pharmacy, and, confining himself merely to detect 

 diseases, leave to the pharmaceutist to point out appropriate 

 remedies ? As absurd would it be to assert that, though che- 

 mistry is one of the best aids of horticulture, the gardener 

 should leave its application to others. I shall conclude my 

 observations on this point with two extracts, one from the pen 

 of Dr. Henry, the second from that of Mr. Kirwan. " Any 

 knowledge," says Henry, " that can be acquired respecting 

 soils and manures, without the aid of chemistry, must be vague 

 and indistinct, and can neither enable its possessor to produce 

 an intended effect with certainty, or to communicate it to 

 others in language sufficiently intelligible. Thus we are told 

 by Mr. Arthur Young, that, in some parts of England, any 

 loose clay is called marl ; in others marl is called chalk; and 

 in others clay is called loam. From so confused an applica- 

 tion of terms, all general benefits of experience in agriculture 

 must be greatly limited. Chemistry may, to agriculturists, 



