FERTILIZERS. 253 



with coal ashes, and.it is true it would not be profitable to haul them a great distance ; still, 

 on all the clay lands within three or four miles of a city or village, coal ashes would remunerate 

 farmers for their expenses in transporting them, as this is the principal expense incurred. Their 

 effect is both chemical and mechanical, furnishing lime, magnesia, alkali and some phosphates, 

 and creating a lighter condition. 



Sulphate of Potash. Sulphate of potash is made by the union of sulphuric acid and potash : 

 but it is obtained from the decomposition of nitre by sulphuric acid, in the manufacture of 

 nitric acid. It is found, by experiment, to increase the products of the soil. Its price, however, 

 forbids its use, and especially so long as cheaper materials are at hand, and are also equally 

 useful as fertilizers. 



Chloride of Potassium. This compound is found in the stems of potatoes ; also in corn- 

 stalks and beans. It is not, however, known to exist in the seeds of the cereals. Occurring as 

 it does in the vegetable kingdom, it is probable that it is of some use : its value, however, has 

 not been determined. 



Nitrate of Potash, {Salt Petre.) This salt is formed under circumstances identical with 

 those described under nitrate of lime. A source of nitrogen is provided in the organic matters. 

 The mineral matters are ashes, consisting of lime, potash, soda, magnesia, etc. An impure 

 nitrate is first formed by the union of its elements. In the vicinity of old building", as out- 

 houses and places where cattle are fed and kept, the soil becomes charged with nitre ; but 

 being a very soluble salt, it does not accumulate, except where it is protected by buildings, in 

 consequence of filtration of rain water through the soil. In regions where no rains fall the 

 nitre is produced spontaneously, and forms beds of considerable extent : but where such accu- 

 mulations occur, or even where there is only a slight excess of nitre, the soil becomes barren. 

 Nitre, in small quantities, promotes the growth of plants, and increases the product some- 

 what beyond the ordinary amount ; it increases always the amount of straw. When used as 

 a top dressing for barley, the crop has amounted, in some experiments, to between thirty-seven 

 and thirty-eigjit bushels to the acre, laid on at the rate of fourteen pounds to one-eighth of an 

 acre. This is by no means common. The straw in this case was considerably greater than 

 that produced by nitrate of soda, which gave fifty-two bushels to the acre. I notice this expe- 

 riment by Mr. Heming, as it shows that where circumstances are unfavorable the application of 

 saline manures will be an injury. The top dressing with nitre was succeeded by dry weather, 

 or with but little rain, and the consequence was that the plants were burned, as the expression 

 is. There is, therefore, some risk always in the use of saline fertilizers : they require sufficient 

 rain to effect a very dilute condition, and which will also carry them into the soil. If ap- 

 plied early, or with the first rains of the season, they get an early start, and when the land is 

 covered with herbage, or well shaded, there is little danger of the crop suffering an injury from 

 drought. It the top dressing is delayed till after the early rains have fallen, the risk of an 

 injury from want of rain is considerable. When nitre can be procured at a cheap rate, its ap- 

 plication to meadows proves more economical than to the cereals, inasmuch as it seems to be 

 an established fact that the nitrates promote the growth of stalk and herbage. 



