372 Catalogue of Works on Gardening, Sfc. 



work of a strictly elementary character, except in the useful but expensive 

 ' Ladies' Botany ' of Dr. Lindley, which he would strongly recommend to 

 such of his readers as can gain access to it. Being persuaded, however, that 

 through the aid of this system alone can any definitive idea be gained, of the 

 vast extent and varied aspect of the vegetable kingdom, he has not hesitated 

 to employ it here. In his selection of orders, he has regarded those as having 

 the best claim to notice, which contain plants of greatest importance to man, 

 or which present some remarkable peculiarities of structure or habit ; a few, 

 however, which possess neither of these distinctions, have been introduced, 

 as containing well-known British plants, or on account of their great abundance 

 in particular spots of the globe. The Cryptogamia have not been treated of 

 in this part, since a popular view of their character was included in the 

 former one, and further details would not have possessed sufficient interest." 

 Both the letterpress, and the cuts are chiefly taken from Dr. Lindley's 

 Ladies' Botany and School Botany. 



Elements of Agricultural Chemistry and Geology. By James F. W. Johnston, 

 M.A., F.R.S., Honorary Member of the English Agricultural Society; 

 and Author of " Lectures on Agricultural Chemistry and Geology." 

 ]2mo, pp. 237. Edinburgh and London, 1842. 



Of all the different works which have lately been published on the chemistry 

 of agriculture, that now before us appears to be the most likely to be of real 

 service to the practical man. It is clear and comprehensive, without being 

 needlessly profuse ; and what gives the practical farmer a direct interest in 

 every statement is, that its application to culture or produce is pointed out 

 in such a manner as to be clearly understood. In a word, Professor John- 

 ston is at once a scientific and a popular writer. This little work is to be 

 considered as a familiar outline of the subjects of agricultural chemistry 

 and geology, which are treated of more at large in the professor's Lectures, 

 now publishing in numbers ; and we have no doubt it will induce many per- 

 sons to procure and study the Lectures ; who, without the fascination, if we 

 may so term it, of the Elements, would never have ventured upon the task 

 of studying the larger work. 



The author commences by pointing out the distinction between the 

 vegetable or organic parts of plants, and the earthy or inorganic. The latter 

 are discovered by the ash left after burning. The quantity of ash left by a 

 ton of wheat straw is sometimes as much as 360 lb. ; while a ton of the grain 

 of wheat leaves only about 40 lb. ; and a ton of oak wood only 4 or 5 lb. 

 The organic parts of plants, therefore, when in a perfectly dry state, con- 

 stitute from 85 to 99 per cent of their whole weight. It is chiefly culmife- 

 rous plants (hay and straw) that contain so much as 10 per cent of inorganic 

 matter. The organic part of plants consists of carbon, a solid substance, and 

 of hydrogen, oxygen, and nitrogen, peculiar kinds of air. One half the weight 

 of most plants, when dried, consists of carbon, about one third of oxygen, 

 5 per cent of hydrogen, and from 2 to 3 per cent of nitrogen. These 

 elements are chemically combined ; a result produced in art by the appli- 

 cation of heat, and in nature by vital action. By either of these means two 

 or more substances may be united together, so as to form a third possessing 

 properties different from both. Carbon, and the other substances which 

 constitute the food of plants, enter by the minute pores of the roots, and the 

 pores in the green part of the leaves and of the young twigs. Carbon is 

 absorbed from both the soil and the air in the form of carbonic acid, and 

 from the soil in the form of the humic and ulmic acids. The hydrogen and 

 the oxygen are absorbed in the form of water, which is a chemical compound 

 of these gases, and the nitrogen is absorbed in the form of ammonia or 

 nitric acid. As a specimen of the manner in which Professor Johnston 

 treats his subject, we shall quote what he says of ammonia and nitric acid ; 

 two substances of immense importance in vegetation, and peculiarly interest- 



