SCIENTIFIC HISTORY OF A PLANT. 



In speaking of the imperishability of matter, I alluded to the changes which it is con- 

 stantly undergoing, because the earth, from the first moment of creation, has been sub- 

 ject to the never-ending play of natural forces; and by looking at the present state of the 

 globe, and then by reading its past history, the mutation of all material substance is tho- 

 roughly illustrated. 



The progress of disintegration has not been much investigated; but Liebig has collected 

 into his *' Agricultural Chemistry" the results of most experiments on this subject. He 

 divides the process of disintegration into two groups — waste, the result of mechanical 

 force, and disintegration, properl}' so called, a product of chemical action. It by no means 

 follows that both disintegration and waste may not be simultaneously taking place in the 

 same rock, or in other AVords, both chemical and mechanical causes operating in unison, 

 and by their union producing great effects. 



The action of carbonic acid and water is generally to liberate in a soluble form the al- 

 kaline bases, producing frequently as an ultimate product, hj^drate of silica, before which 

 is often formed a soluble silicate. I presume that a descriptive detail of the pi'operties of 

 silicic acid would be superfluous; but an experiment of that talented chemist, Lavoisier, 

 deserves notice here. 



Silicates are more or less decomposed by the action of hot water; the opacity of the 

 windows in hotbeds is an example of this. Lavoisier, on distilling some water from a clean 

 glass vessel, found it left a residue; on weigliing it, he also found that the glass retort had 

 lost in weight what the water had gained: from this experiment it was obvious that a por- 

 tion of the silica of the ghuss had been dissolved during the distillation. 



It is needless to enumerate all the substances upon which chemists have operated; suf- 

 fice it to say that their experiments have had a very extended range, and that they con- 

 firm all the statements made by those who preceded them in this investigation. In this 

 memoir there are two points of especial interest. One is, that the alkalies are not quite so 

 essantial to the disintegration and decomposition of mere rocks, as it was at first suppos- 

 ed : for hornblende, epotite, chlorite, and rocks composed mainly of these substances, un- 

 derwent rapid decomposition by pure as Avell as by carbonated water, and this Avithout 

 calling in the agency of an alkali; this experiment accounts for the fact that rocks of this 

 kind are often moie readil}' decomposed by meteoric agencies than are felspars : it enables us 

 to trace the simple process hy which plants arc furnished with the lime and the magnesia 

 they require, without our having recour.se to any mysterious decomposing power of the 

 roots of the growing vegetable. The second and most important result is, that potash, 

 soda, and tlieir carbonates, but especially carbonate of pot sh, is volatile at a red heat, — 

 that many plants contain much alkali, whci'eby a very little is found in the ashes after 

 incineration. So, by this incineration of the ashes of a plant, according to the ordinary 

 rules for the analysis of vegetables, the Professors Rogers' statements show that a very 

 large amount of error must not only have been by such analyses introduced, but b}'^ them 

 parptuatzd. The ashes of anthracite, of bituminous coal, of lignite, contain not a trace 

 of alkali, but digestion with water previously to incineration, reveals to us their presence — 

 thus adding another proof to the vegetable origin of coal. 



I have not gone into the minutiae of an}' actu:il decompositions which take place during 

 the disintegration of certain rocks, because my object is more to point out a train of 

 thought than to dwell upon the facts by which these reflections may be produced. Our 

 facts may be likened to the landmarks of the journey, but their attainment is not its ulti 

 iin. 



mentioned that certain plants require soils containing some particular mineral 



