Retrospective Criticism. 599 



tion must be repeated when the soil is dry an inch or two deep. When a less 

 quantity of water is supplied, it often does more injui'y than good to plants ; 

 for when in want of water the roots penetrate deep, and, under such circum- 

 stances, a small quantity of water on the surface checks the capillary attraction : 

 thus the roots that are grown deep, which are those on which the plant is 

 made to depend in seasons of great droughts, are deprived of their supply of 

 water, and the plant exerts itself to throw out horizontal fibres : by the time 

 these are formed, and the young shoots extended, the supply of water on the 

 surface again fails, and they are again checked, and perhaps destroyed : thus 

 the efforts of the plant being uselessly directed between the extremes of a 

 supply and a deficiency of water, it naturally declines in its growth ; and hence 

 the general opinion, that watering in dry weather injures more than it benefits 

 plants." (p. 52, 53.) 



In the part which treats upon the food of plants, among other things of im- 

 portance, we find the fact stated, that carbonaceous matter cannot be made 

 available for the nourishment of plants, unless it has previously been combined 

 with animals or vegetables in a living state. Much importance is, with appa- 

 rent propriety, attached to the different results which are the effect of carbona- 

 ceous matter in union with hydrogen, and when in combination with oxygen. 

 When the carbonaceous matter lies deep, or in stagnant water, carburetted 

 hydrogen or hydrocarbonate is formed, which, if they do not produce disease, 

 are sure to encourage the developement of luxuriant branches and leaves, but, 

 at the same time, to retard the processes of fructification, which the application 

 of oxycarbonate advances. Hence, with much propriety, the author advocates 

 shallow planting for fruit trees j having grown the best peaches upon 6 in. 

 depth of soil resting upon a stone pavement. Hence, also, not merely in the 

 case of fruit, but in that of vegetables and crops of any description, where good 

 flavour and wholesome nutritious matter are more desirable than bulk or mag- 

 nitude, the author not only is adverse to the burying of dung or vegetables in 

 a rank state, but advocates the general use of surface manuring, contending 

 that, although the manure be reduced in its weight by the evaporation of its 

 water, " the nutritive principle will be rather increased by the attraction and 

 combination with oxygen ; as thus the carbonaceous matter will be rendered 

 soluble, and the separation and combination of nitrogen effected ; and what is 

 carried off will only be carburetted hydrogen gas, which would have been more 

 injurious than beneficial if retained." (p. 103.) Having given us the signs 

 and consequences of carbonaceous matter in an inert state, or in combination 

 with hydrogen, the author attaches due importance to the application of lime 

 and alkaline salts ; the former, when slaked, for rendering carbonaceous matter 

 soluble, and the latter for effecting the same purpose, and from parting with 

 their oxygen, changing hydrocarbonate into oxycarbonate. He laments that 

 so much nutritive matter should be allowed to drain away from our dunghills, 

 as this matter consists partly of the urine of animals, all of which more or less 

 contains alkaline salts ; and recommends that it should either be thrown back 

 upon the heap, or used pretty fresh, as liquid manure, diluted with from four 

 to six times its quantity of water. In making liquid manure from rotten dung, 

 he recommends the addition of alkaline salts in the proportion of 1 ounce of 

 potash to 1 cubic ft. of dung, and 4 gallons of water ; and, if necessary, for 

 hastening the decomposition, 1 quart of the powder of slaked lime. A good 

 deal is said respecting the effectiveness of the serum of blood as a food for 

 plants, respecting which a long communication appeared some time ago in this 

 Magazine. When, from an excess of hydrocarbonate, " the leaves of plants 

 are large and spreading, of a yellow colour, and the blossoms fall off" prema- 

 turely, or the fruit falls off at the kerneling or stoning, or fails to arrive at 

 maturity," the author has used with much success " a solution of nitre, a little 

 while before the blossoms open, in the proportion of 2 ounces of nitre to 6 

 gallons of water," pouring it on the soil as far as the roots extend " (p. 105.) 

 After bearing for two or three years, of course the trees would require a fresn 



