164 



THE GAEDENEE'S ASSISTANT. 



roots of plants, and to the burned clay contain- 

 ing a much greater proportion of soluble alkalies, 

 more especially of potash and soda, than the 

 unburned clay, a considerable portion of the 

 alkaline substances contained in the latter being 

 rendered soluble in the process of burning. 

 Burned clay, by improving the texture of the 

 soil, and by supplying a greater amount of 

 alkalies to plants, must prove beneficial to all 

 crops ; but it is more especially on Turnips, 

 Carrots, and Potatoes, fruit-trees, or other plants 

 requiring a large amount of potash, that the 

 beneficial effects of this manure are most con- 

 spicuous. 



The state to which the clay is reduced by 

 burning is of great importance; for if exposed 

 to too great a heat, it will become of the nature 

 of brick, and its alkaline ingredients will be less 

 soluble than if burning had not been resorted to. 

 The clay should only be slightly burned, and so 

 that it may readily crumble down. The effect 

 of burning is to get rid of all the organic matter, 

 but the mineral constituents which plant-life 

 had abstracted from the soil remain, and they 

 are so transformed by fire as to be easily assim- 

 ilable by future crops. 



The following is Sir H. Davy's analysis of the 

 ash of burned turf: — 



Per cent 



Carbonate of lime, ... ... ... ... 40 



Sulphate of lime (gypsum), 5i 



Charcoal (carbon), ... ... ... ... 4i 



Potash and magnesia, H 



Iron oxide, . ... ... ... ... 7h 



Insoluble earthy matters, 41 



100 



Burning has really very much the same effect 

 that liming has in sweetening the soil, and in 

 setting free quantities of inorganic matter which 

 were previously in a locked-up or inert con- 

 dition. 



Gas Waste. — The ammoniacal liquor obtained 

 in making gas is employed as a manure, and 

 with good effects. It consists of a solution of 

 the carbonate, hydrosulphate of ammonia, and 

 other salts of the same base. All its value is 

 due to the ammonia which it contains; the 

 amount of this is subject to considerable vari- 

 ation, but rarely exceeds 2 per cent. On account 

 of its caustic nature, gas water should always be 

 applied with caution, and it should be diluted 

 with five or six times its bulk of water, other- 

 wise it is certain to burn up whatever crops it is 

 applied to. 



Gas water is chiefly applied to grass, and may 

 be used at the rate of from 100 to 200 gallons 

 per acre. Field Cabbage, and any of the Cab- 



bage tribe, in a garden will be greatly benefited 

 by an occasional watering with gas liquor, as 

 will also Easpberries and Black-currant trees, 

 but, for the reason previously given, it must be 

 diluted with water. This, of course, involves a 

 considerable amount of labour; and it may be 

 observed, that the practice is only applicable to 

 light soils. 



Gas lime is the lime which has been employed 

 in purifying the gas, and it always contains a 

 large quantity of the sulphuret of lime, the action 

 of which on vegetation is unquestionably injuri- 

 ous. For this reason, the use of gas lime in a 

 fresh state as a manure is not to be recommended. 

 I After lonsj exposure to the action of the air and 

 water, the hydrosulphuret of lime is converted 

 | into sulphate of lime or gypsum, and its injurious 

 action ceases. Gas lime is then merely a mixture 

 of gypsum and lime, and is usually free of in- 

 jurious compounds, and. a manure which, if dug 

 into the soil during winter, will be found bene- 

 ficial in preventing club-foot, and the disease 

 known as " fingers and toes " (Anbury) in the 

 Cabbage family. 



Gas tar consists almost entirely of carbon and 

 hydrogen, and is of little or no value as a ma- 

 nure, though it has been occasionally used as 

 such. 



Lime has long been employed as a manure, and 

 its application to the soil has been attended with 

 great success, especially when preceded by drain- 

 age. Lime does not occur in nature in a free 

 state, but united with carbonic acid, forming 

 carbonate of lime, it is found in abundance. 

 There are many varieties of carbonate of lime, 

 but the most common are limestone and chalk. 

 Pure carbonate of lime consists of 56*3 per cent 

 of lime and 43 7 per cent of carbonic acid. On 

 being exposed to a strong red heat, carbonate of 

 lime loses its carbonic acid, and quicklime is pro- 

 duced. This substance has a powerful affinity 

 for water, absorbing it rapidly when brought in 

 contact with it, and more gradually when ex- 

 posed to the atmosphere; in both cases, a com- 

 pound of the hydrate of lime, consisting of 28 - 5 

 parts or 1 equivalent of lime, and 9 parts or 1 

 ' equivalent of water, is produced. 



The process by which the hydrate is formed 

 is called slaking, and it is always attended with 

 a great increase of temperature. The hydrate 

 itself is termed slaked lime. After long exposure 

 to the air, the hydrate of lime parts with its 

 water, absorbs carbonic acid, and again becomes 

 carbonate of lime. 



Quicklime is extremely caustic, decomposing 

 all animal and vegetable matters with which it 



