78 On the Injiuetice of (he 



faction, or about to be so, that thev are proper for being 

 mixed with it, and the gases disengaged by the putret'actioa 

 rendered usetul as nourishment tor phuits ; as experience 

 shows that tew plants thrive wlien situated on an accumu- 

 lation ot" organic bodies in a state of full putrefaction. 



Besides the increased volume, and the advantages con- 

 nected with it, mould mixed with the bottom earth opposes 

 a greater resistance to wind and water, and thereby secures 

 to the farmer the fruit of the exertion and industry he must 

 employ to reduce organic bodies to a state of putrefaction. 



The bottom earth, with which in agriculture organic mat- 

 ters are mixed, does not consist of one kind, but is always 

 .mixed with decomposed rocks, as in conmion it is nothmg 

 else, most of which contains silex, argil, lime, and mag- 

 nesia. 



Each of these kinds of earth possesses chemical and me- 

 chanical properties which often exercise a contrary action 

 on each other, which does not produce the most beneticial 

 eftect on the growth of plants, and therefore it may be of 

 use to the agriculturist to know with what pure earths his 

 bottom earth is mixed. 



It would be extending the present essay to too great a 

 lenirth to give a circumstantial description of the proee« 

 employed by several eminent chemists to decompose vege- 

 table earth ; I shall thcrttfore comfine myself to an account 

 of the component parts of boilom earth, together with its 

 properties and action, in such a manner that we may 

 thence be enabled to explain fronrit the views of the farmer 

 in the ditterent operations he employs. 



Among the number of the component parts of bottom 

 tarth, are : 



1st, Siliceous Earth. — It appears in general partly in a 

 compact form, as in sand and large fragments of quartz, 

 partly in a fine light form, in which it is more intimately 

 mixed with the other kinds of earth not visible to the eye, 

 and can be separated only by the help of chemistry. It does 

 not every where occur in the same proportion : in many 

 districts it forms, like sand, iiearly the whulu of the bottom 

 earth, and in others it is scarcely perceptible. Acids, the 

 fluor acid excepted, have no action on it : with alkalies, in 

 diti'erent proportions, it forms glass, or the so-called oil of 

 flints, in which union it is soluble in water ; and in this 

 state, when it exists, can be taken up very well by plants ; 

 in which, however, it forms only an accidental component 

 part. 



The mechanical action of this kind of earth, by which it 

 4 aiodtrates 



