33 



at places where trees have been felled, often block by 

 impenetrable barricades the accessible lines of traffic through 

 the forests, and are frequently the cause of the extensive 

 conflagrations of the woods, by placing so much combus- 

 tible, dry and mostly oily material within the easy reach 

 of the current of flames. Should, unfortunately, the fiery 

 element have anywhere swept through the forest, it may then 

 prove advantageous to collect the fresh ashes before they are 

 soaked by rain, with the object of extracting thus large 

 quantities of potash. The whole process of potash prepara- 

 tion being one of the simplest kind, and involving only a very 

 trifling expense in casks and boiling-pans, can be carried out 

 anywhere as a by-work, the profit thus being not reduced by 

 skilled or heavy labour or by costly plant. The demand for 

 potash must always be considerable, as it is required for the 

 factories of nitre (particularly from soda saltpetre), one of the 

 three principal ingredients of gunpowder and blasting powder; 

 it is needed also for glass, alurn, various kinds of soaps, dyes 

 and many chemicals.* 



Potash, although universally distributed, is best obtained in 

 the manner indicated. I may remark, however, though 

 deviating from my subject, that it is one of the most potent 

 constituents in all manures, being especially needed in the 

 soil for all kinds of root-crops, for vine and maize; nor can 

 most other plants live without it altogether, although the 

 quantity required may be small; but I must add, for manuring, 

 potash by itself would be far too valuable. 



Almost every kind of forage affords potash salts, these being 

 among the necessaries for the support of herbivorous animals. 

 Their undue diminution in food is the cause of various dis- 

 eases both in the animal and vegetable world; or predisposes, 

 by abnormal chemic components of the organisms, to disease. 



The muscles of the human structure require a comparatively 

 large proportion of carbonate of potassa ; it is also absolutely 

 required in blood, predominating in the red corpuscles. Plants 

 grown in soil of rocks containing much felspar such as granite, 

 gneiss, syenite, some porphyries, diorite are always par- 

 ticularly productive in potash, potassium entering largely 

 into felspatic compounds. The latter mineral yields in most 

 cases from twelve to fourteen per cent, of potassa, which, if 



* Flint-glass contains about a fifth pure pearlash ; crown-glass, 

 the best of window-glass, rather more than a quarter. Some potash- 

 nitre is wanted also in either case. 



