upon Native Vegetables. 59 



place in stagnant water ; but most of all to that great revolu- 

 tion of the earth's surface, which we believe to have taken place 

 at a remote period. The causes, however, concern not the 

 present object. It is enough to know, that many of our plains, 

 valleys, and the sides of mountains, are covered by a mass of 

 sand and mud, not derived from the rock immediately beneath. 

 The decay of vegetables, and the operations of agriculture, 

 are gradually increasing the foreign matters upon the surface, 

 and must be tending to separate the vegetable kingdom still 

 farther from the rocks. 



Let us next examine the cases, and they are not very numerous 

 wherein a considei'able proportion of the soil is derived from the 

 rock immediately below. It is, then, to be here mentioned, as an 

 argument against the influence of rocks, even in those instances 

 that the mineral ingredients appear to perform a part which is far 

 from being very important to the vegetable economy. Thus Gio- 

 bert mixed together the earths usually found in fertile soils, and 

 in this artificial compound were placed seeds of various kinds 

 which germinated indeed, but did not thrive, and soon perished. 

 Let this experiment be viewed in connexion with others, wherein 

 water alone was supplied. Du Hamel placed in moss or wet 

 sponges beans and pease, which flourished and produced fruit ; 

 and Bennet, by treating vines in a similar manner, found that 

 they produced excellent grapes. From these experiments, it 

 might be inferred, that water by itself is as conducive to the 

 nutrition of vegetables as pure mineral soil moistened with wa- 

 ter. Is there a probability that the principal use of the mineral 

 part of soil is to be a medium for conveying to plants moisture 

 along with matter derived from animal and vegetable sub- 

 stances .'' 



All the foregoing considerations militate much against the 

 opinion that vegetable species are determined by the nature of 

 the subjacent rock ; and, indeed, they appear so strong as not to 

 be overcome unless by strong facts on the other side. In other 

 words, without strong facts the opinion appears to have no kind 

 of footing. Were it to prove to be possessed of a good founda- 

 tion, an interesting inquiry would be as to how the vegetable 

 species arc arranged, with relation to particular rocks, — whether 

 they are mingled in a miscellaneous manner, or grouped together 



