I04 Notes and Gleanings. 



In an article among the " Notes and Gleanings " of the December number, 

 by I. F. H., occurs the following : " It is curious to inquire whether the vegeta- 

 tion which originated the coal contained potassium ; and, if so, what became of 

 it." A few words on the subject may not be amiss. It would require a trea'^'ise 

 of some length to explain, even approximately, why coal is so deficient in the 

 inorganic salts necessary to vegetable life, and the many causes that have co- 

 operated to produce this result. The following are a few of the principal reasons, 

 stated as briefly as possible : — 



I st, The plants of the coal period were deficient in inorganic consfittients dur- 

 ing life. — A natural consequence of their surroundings. The climate was 

 everywhere insular, sub-tropical, and very equable ; the atmosphere reeked with 

 mists and miasmata ; rains were probably excessive. Here are excellent con- 

 ditions for rank growth ; and the vegetation of the coal-forests was exuberant 

 beyond conception. It consisted largely of enormous cryptogamous plants, rooted 

 in a soil of decayed vegetable matter saturated with water, and often flooded. 

 It is plain that plants of this nature, built up of moisture and gases, would 

 yield very little ashes compared bulk for bulk with the long-lived, wood-pro- 

 ducing trees of the present day, that require a large supply of material from 

 decomposing rocks for their support. 



2d, Most of the soluble inorganic matter was separated during their con- 

 version into coal. — Coml^ustion and decay are like processes. With free access 

 of air, their products are carbonic acid and water ; but, when the supply of air is 

 imperfect, more or less carbon remains unoxidized. Charcoal-burning is a famil- 

 iar example. The plants producing our coal all grew in fresh marshes, and decayed 

 under water., where very little air reached them : those confined to higher lands 

 yielded by their decay no coal, — only soil and gases. The water surrounding 

 these decaying plants dissolved out most of their alkaline salts and other soluble 

 matters: these were partly absorbed by superincumbent vegetation, and partly 

 swept into the sea by streams. 



3d, The traces of alkalies and soluble matter that may exist in perfected coal 

 are liable to be expelled by after-processes. — Without taking into account any of 

 the profound and obscure changes whereby soft coals have been converted into 

 anthracite in the earth, the temperature of its combustion in our stoves and fur- 

 naces is sufficient to reduce to the elementary state, and volatilize potassium or 

 sodium compounds. The same is true of phosphates. 



Whether coal-ashes are of any practical value, or not, depends mainly on the 

 source from whence they are obtained. Pure anthracite-ashes contain nothing 

 available except a little sulphate of lime (gypsum, plaster), for which it is not 

 worth hauling. It is of no value but as an absorbent or diluent of strong ma- 

 nures. But very little coal-ashes is pure. The refuse from a stove or furnace 

 in which the fire is daily kindled with wood is altogether too valuable to be 

 thrown away, not for itself, but for the wood-ash'es mixed with it. When we 

 hear of plants growing readily in coal-ashes, this is probably the kind meant. 



D. W. B. 



