2 INTRODUCTION. 



immediately adjoins one which has long re- 

 mained undisturbed for pasture, and where 

 the vegetable mould is exposed on the sides 

 of a ditch or hole. The subject may appear 

 an insignificant one, but we shall see that 

 it possesses some interest ; and the maxim 

 " de minimis lex non curat," does not apply 

 to science. Even Elie de Beaumont, who 

 generally undervalues small agencies and 

 their accumulated effects, remarks.* " la 

 " couche tres-mince de la terre ve'getale est un 

 " monument d'une haute antiquite, et, par le 

 " fait de sa permanence, un objet digne d'oc- 

 " cuper le geologue, et capable de lui fournir 

 " des remarques interessantes." Although 

 the superficial layer of vegetable mould as a 

 whole no doubt is of the highest antiquity, 

 yet in regard to its permanence, we shall here- 

 after see reason to believe that its component 

 particles are in most cases removed at not a 

 very slow rate, and- are replaced by others 

 due to the disintegration of the underlying 

 materials. 



As I was led to keep in my study during 

 many months worms in pots filled with earth, 



* ' Lecons de Geologie Pratique,' torn. i. 1845, p. 140. 



