508 C. Darwin, Esq., on the 



to form a thick stratum must be considerable. In the peaty field, in the 

 course of fifteen years, about three inches and a half had been well prepared; 

 but it is probable that the process is continued, though at a very slow rate, 

 to a much greater depth. Every time a worm is driven, by dry weather or 

 any other cause, to descend deep, it must bring to the surface, when it empties 

 the contents of its body, a few particles of fresh earth^. Thus, the manures 

 added by man, as well as the original constituent parts of the soil, become 

 thoroughly mingled, and a nearly homogeneous character is given to the 

 whole. 



Although the conclusion may appear at first startling, it will be difficult to 

 deny the probability, that every particle of earth forming the bed from which 

 the turf in old pasture land springs, has passed through the intestines of worms ; 

 and hence the term " animal mould" would in some respects be more appro- 

 priate than that of " vegetable mould." 



I may conclude by remarking, that the agriculturist in ploughing the ground 

 follows a method strictly natural ; he only imitates in a rude manner, without 

 being able either to bury the pebbles or to sift the fine from the coarse 

 earth, the work which nature is daily performing by the agency of the earth- 

 worm. 



Note. — Since my communication on the " formation of mould," read on 

 the 1st of November, I have received from Staffordshire an account which 

 corroborates the statements then made, on the apparent sinking of objects 

 placed on the surface of turf land. The first case I mention only because 

 the substance is different from those previously described. In the spring of 

 1835 a boggy field, which had long remained as grass land, was so thickly 

 covered with sand that the whole surface appeared of a red colour. At the 

 present time, namely about two years and a half afterwards, the sand forms 



* Mr. W. Lindsay Carnagie of Kimblethment, writing from Scotland to Mr. Lyell on the 

 subject of this paper, as it is given in the Proceedings, stales, that in clearing away a stift' clayey 

 soil above a stone quarry, he has seen worms in small chambered passages between seven and 

 eight feet below the surface. The black mould on the clay was there two feet thick. Mr. Car- 

 nagie observes, also, in his letter, that the Scotch farmers, from a belief that the lime itself has 

 some tendency to sink, are afraid of putting it on ploughed land until just before it is laid down 

 for pasture. He then adds, *' Some years since, in autumn, I laid lime on an oat-stubble and 

 ploughed it down ; thus bringing it into immediate contact with the dead vegetable matter, and 

 securing its thorough mixture through the means of all subsequent operations of fallow ; I was 

 considered, in consequence of the above prejudice, to have committed a great fault, but the result 

 was eminently successful, and the practice partially followed. By means of Mr. Darwin's ob- 

 servations, I think the prejudice will be entirely removed," — June 1838. 



