SOILS, SPECIFIC GRAVITY OF. 478 



SOWING FOR TREES. 



5 to 12 per cent, of humus that is, de- 

 composed vegetable and animal matter. 



(e) Marly soil is the debris of limestone 

 rock, decomposed and reduced to a paste. 

 It contains from 5 to 20 per cent, of car- 

 bonate of lime. 



(/) Loamy soil is soil in which the pro- 

 portion of clay varies from 20 to 25 per 

 cent. ; sand, and various kinds of alluvium, 

 making up the remainder. 



Soils, Specific Gravity of. 



Loudon gives the following methods for 

 determining the specific gravity of any soil, 

 and its capacity for retaining water : 



(1) " The specific gravity of a soil, or the 

 relation of its weight to that of water, 

 may be ascertained by introducing into 

 a phial which will contain a known 

 quantity of water equal volumes of water 

 and of soil, and this may be easily done 

 by pouring in the water till it is half full, 

 and then adding the soil till the fluid rises 

 to the mouth ; the difference between the 

 weight of the soil and that of the water 

 will give the result. Thus, if the bottle 

 contains 400 grains of water, and gains 

 200 grains when rilled half with water 

 and half with soil, the specific gravity of 

 the soil will be 2 that is, it will be twice 

 as heavy as water ; and if it gained 165 

 grains, its specific gravity would be 1,825, 

 the water being 1,000," 



(2) " The capacity of a soil for retaining 

 water may be thus ascertained. An equal 

 portion of two soils, perfectly dry, may be 

 introduced into two tall cylindrical glass 

 vessels, in the middle of each of which 

 a glass tube has been previously placed. 

 The soils should be put into each in the 

 same manner, not Compressed very hard, 

 but so as to receive a solidity approaching 

 to that which they possessed when first 

 obtained for trial. If, after this prepara- 

 tion, a quantity of water be poured into 

 the glass tubes, it will subside, and the 



capillary attraction of the soils will conduct 

 it up the cylinders towards the tops of the 

 vessels. That which conducts it most 

 rapidly, provided it does not rise from the 

 weight of the incumbent column of water 

 in the tube, may be pronounced to be the 

 better soil." 



Sowing for and Planting Trees, 

 &c. 



There are two modes of stocking a park 

 or ornamental pleasure-grounds with trees 

 and shrubs, namely, sowing and planting. 

 Let us glance for a moment at the merits 

 and demerits attaching to these two 

 methods. They may be summed up 

 briefly in a very few words. To create a 

 wooded tract of land by sowing is a slow 

 but safe and sure process, bui the results 

 desired can only be realised by a lapse of 

 many years. To do so by planting is a 

 rapid but by no means so certain a way 

 of going to work, as transplanted trees and 

 shrubs will often perish, and others must 

 be planted in their place ; but when once 

 the plants are rooted and well established, 

 the start they have obtained over those 

 which are raised from seed will obviate the 

 years of patient waiting which must other- 

 wise be endured by those who sow. 



In what, then, it will be asked, is the 

 advantage of sowing, and for what reasons 

 can it be recommended ? Sowing is cheaper 

 and safer than planting, and is therefore 

 more desirable than planting, when the 

 chief object in view is to transform an 

 untimbered piece of ground into a wood- 

 land, or when a person can afford to wait 

 some years before he commences building 

 on the land on which he has sown seeds 

 for the purpose of producing timber. The 

 best writers on arboriculture are agreed on 

 the desirability of sowing, on account of 

 its economy and safety, and declare that 

 trees "which are transplanted will never 

 arrive at the size of those which stand 



