MANURES AND THEIR USES. 
219 
calcium hydrate and calcium carbonate with sulphite and 
sulphide of lime. The two latter compounds are in themselves 
poisonous to plant-life, but they are both converted into gypsum, 
or sulphate of lime (a plant-food), by exposing the gas-lime to 
the action of the atmosphere. 
Gas-lime is best applied in the autumn at the rate of two to 
five tons per acre, but as a plant-food this manure has much less 
value than either quicklime or carbonate of lime. 
To prepare fresh gas-lime for use in the garden, it may be 
spread out on a layer of pond-mud, night-soil, or coarse vegetable 
refuse and exposed to rain and air. It is an excellent agent in 
decomposing seaweeds for manure. 
Potash Manures. 
Every plant requires a certain amount of potash for its 
growth and development. Potash is said to play an important 
part in the nutrition" of chlorophyll, and its presence is 
absolutely indispensable to the formation of starch in the green 
leaves of plants. Kainit, or crude potash salts, is the commonest 
form in which potash is now employed as a manure. 
It seems to be particularly suited for Potatos, as it both 
increases the weight of the produce and improves the quality of 
the tubers. It may be used at the rate of 3 cwts. per acre, and 
mixed with superphosphate, nitrate of soda, and ammonium 
salts. 
Dr. Voelcker, by analysis, shows kainit to contain : — 
From 23 to 25 per cent, sulphate of potash, 
„ 14 to 28 „ salts of magnesia, 
,, 30 to 48 „ chloride of sodium. 
An excess of potash manures, however, is said to have a tendency 
to foster the development of parasitic fungi. 
Seaiueeds as a Manure. 
In the Channel Islands and on the Scottish and Irish coasts, 
and in the Isle of Wight, the seaweeds are used as manure. The 
weeds are carted oif the shore during the autumn and winter, 
and are placed in large heaps to rot, sometimes mixed with 
coarse farmyard manure and gas-lime. After it has thoroughly 
decomposed it is applied to the land at the rate of about 10 or 
15 tons per acre. 
