Metrospective Criticism, 461 



treats that most extraordinary hallucination of Dr. Alexander Murray 

 which prefaces Mr. Thomson's remarks. Dr. Murray sets out by saying 

 that he has " endeavoured to discover whether, in the comparatively 

 limited tract to which his observations relate, any decided connection could 

 be traced between the native plants and the soils wherein they are found;" 

 and he concludes that there " is not in science a more hopeless labour than 

 the attempt to discover an unvarying and necessary relation between most 

 plants and the soils wherein they are found." I may, in the first place, 

 observe, that Dr. Murray here entirely changes the terms of his proposition. 

 There is a vast difference between a " decided connection," and " an un- 

 varying and necessary relation." But when the doctor proceeds to add, 

 that, " except in point of moistness, compactness, and depth, soils have, in 

 general, no cognisable relation to their vegetable products," I appeal to 

 every farmer, to every gardener, to every botanist, whether daily and hourly 

 experience does not prove this proposition to be unfounded. If this is 

 " the result of the doctor's observation," his sagacity is but small ; and 

 when he asserts that " it appears, when well examined, no less to accord 

 with reason than experience," we may discern that the doctor's " reason " 

 is even less than his sagacity. The reason he assigns is, that " if we 

 examine Britain, we find the soils in all places composed mainly of silica, 

 alumina, magnesia, and lime, with accidental animal and vegetable impreg- 

 nations." Here he omits to notice the metallic substances ; of which one, 

 at least (iron), acts not an unimportant part in vegetable physiology, to say 

 nothing of the mineral acids, the sulphuric, muriatic, and nitrous, which 

 might deserve to be noticed, as well as the phosphoric and oxalic, citric, 

 malic, and gallic : but, confining ourselves to the earths, how does the 

 doctor's complaint that the soils of Britain consist only of all the known 

 earths (viz. the same of which the rest of the globe is composed) prove 

 that the plants have no assignable connection with the soil ? Does it 

 follow that no plants have a determined election for some one of these 

 simple earths separately ? Does it follow that the numerous combinations 

 which may be made of these four earthy bases with animal and vegetable 

 substances, will not furnish soils extremely distinguishable from each other, 

 differing in many other qualities besides " moistness, compactness, and 

 depth'?" And does it follow that plants may not have very different 

 degrees of election for soils consisting of the same ingredients, combined in 

 different proportions ? The doctor's a priori reasoning on this head does 

 not carry any conviction to my mind : the whole diatribe is really not 

 deserving of the temperate and elaborate refutation with which Mr. Thom- 

 son treats such a mass of crudities. 



Mr. Thomson illustrates his theory by an allegation that " primitive 

 ranges produce the greatest variety and richest specimens of vegetables ; a 

 phenomenon," he says, " derived from the obvious aptitude of such rocks to 

 furnishthe best and richest soil for vegetable growth ;" and " we should 

 contrast," he says, " with these ranges, the poverty and slow productions 

 of secondary and diluvial districts. We should simply contrast the shores 

 of Orme's Head and Devonshire with those of Lancashire, and leave 

 each enquirer to his own conclusions ; satisfied that they would be favour- 

 able to the relations we endeavour to establish." Now, be it observed, 

 that this relation may well subsist, though the example fails. Here I 

 object to Mr. Thomson, that he has fallen into a fault still too common, 

 though numerous naturalists and philosophers of the present age have 

 greatly kept clear of it ; that, instead of amassing facts, and postponing the 

 making of theories until he had abundance of materials, he has rushed into 

 theory-making with a very scanty provision of facts, and has consequently 

 adopted a theory, to say the least of it, extremely doubtful, and which pro- 

 bably will be impugned by more facts than he can array in support of it ; 

 viz. his position, that primitive ranges produce the richest specimens of 



