264 G. H. Kinahan — On the Growth of Soil. 



no matter how small, to tlie thickness of the soil? If the above is 

 the case, how can we account for the growth of peat bogs in Ireland 

 and other countries ? On the site of all peat bogs (or the bogs in 

 the low flat country) there originally was vegetable soil, in which 

 trees and lesser plants grew ; — on this, by the decay of the vegetable 

 matter, a spongy soil was formed that retarded the drainage, and 

 was well fitted for the growth of such mosses as the Sphagnum, 

 which began to luxuriate. The earthworms, it is probable, helped 

 to form the vegetable mould in the first instance, but after the 

 drainage was stopped they could not inhabit the place, therefore 

 their part in the work ceased and only the decay of the succes- 

 sive growth of the plants could add to the surface. The growth 

 of the bogs has been ably treated by Portlock in the Memoirs 

 of the Ordnance Survey of Londonderry, and by Nimmo and 

 Grif&th in their " Bog Eeport," — therefore it is unnecessary to 

 enter further into the subject. Even from Darwin's examjjles it 

 would appear evident that the growth of soil cannot alone be due to 

 worms ; for spread a layer of lime on a field and the worm, to quote 

 that Author, " is unable to swallow coarse particles, and the finer 

 earth lying beneath would be removed by a slow process to the sur- 

 face." Thus eventually all the matter that could be reduced small 

 enough to be swallowed by the worms would be brought above the 

 lime, and only the pebbles and fragments of stones left below ; so 

 that above there ought to be only this fine earth, while below there 

 ought to be only gravel and sand. This is the result that ought to 

 occur if to the worms alone is due the vegetable soil ; but if they 

 worked in conjunction with the decay of the vegetables, and princi- 

 pally in the soil due to that decay, there would be a continual shift- 

 ing of a soil in which few pebbles ever existed. This, however, 

 would necessitate the surface of the subsoil remaining permanent, — a 

 subject, the consideration of which must be deferred till further on in 

 these notes. 



Nearly all the examples put forward by Darwin were observed in 

 rich highly cultivated ground where earthworms abound, therefore 

 the growth of the worm-formed soil must have been more rapid 

 than would ordinarily be the case, and the part added, through the 

 decay of the vegetable matter, may not have been very apparent ; 

 Nevertheless, in one instance, he seems to prove that the vegetable 

 decay, not the earthworms, buried the foreign substances ; namely, 

 that of the boggy field which was covered over with a coat of gravel, 

 and in two years and a half afterwards, there was a peaty layer 

 three-fourths of an inch thick grown over it. Very similar instances 

 occur, and may be examined in many places in Ireland among the 

 reclaimed cutaway bogs, or as they are locally called Moors. These 

 moors are generally tilled for a few years previous to being laid 

 down in grass, after which a coat of marl or gravel is spread on 

 them. If they are to be kept in good heart more gravel or marl 

 from time to time must be applied to them, and the drainage at- 

 tended to ; but if they are neglected, as is too often the case, thej 

 will attempt to return to their former state, and in a short time a 



