G. JS. Einahan — On the Groivth of Soil. 263 



sent, in part at least, the interval (indicated by unconformity) be- 

 tween the Gault and Neocomien. 



"■ The Lower Cretaceous or Neocomien beds are strikingly similar 

 in the two areas. The Clays classed as ' Aptien,' taken together with 

 that called the Speeton-Clay,^ by Mr. Von Strombeck, agree precisely, 

 both lithologically and palseontologically, with the highest beds at 

 Speeton, while the beds called ' Upper Hils ' as closely correspond 

 with the middle portion of the Speeton series, abounding with 

 Exogyra sinuata and Pecten cinctus. 



" The remarkable resemblance, both in mineral character and 

 fossil contents between the two lowest zones (Hils-conglomerat in 

 part of Fr. Ad. Eomer) and the Tealby series of Lincolnshire is 

 also very striking. The yellow sandstones of the Teutoburger Wald, 

 so well described by Prof. Fred. Eomer, are also very similar to the 

 Lincolnshire beds. Studying the palaeontology of these several 

 strata by the light of the Speeton section, I am inclined to believe 

 that they belong rather to the Middle than to the Lower Neocomien." 



{To he continued). 



IV. — Notes on the Growth of Soil. 

 By G. H. KiNAHAN, M.R.I.A., etc., etc. 



PEEVIOUS to writing " Suggestions on Denudation,"^ I had not 

 seen Mr. Darwin's paper "On the Formation of Soil;"^ since 

 then, having read this essay, it appears to me that instead of Darwin 

 proving "the disappearance of stones, etc., needs no growth of soil," 

 he advocates in a great measure the statement put forward in " Sug- 

 gestions on Denudation." For Darwin clearly proves that any 

 foreign substance placed on grass land will be gradually covered up 

 hy a growth of soil over it. This soil, however, he seems to believe 

 to be entirely due to the labour of earth-worms, who excavate in the 

 ground under the foreign substance and deposit over it. From 

 this it would appear that this eminent observer considers that the 

 total thickness of the soil is not increased upwards by mould formed 

 from vegetable decay, but that all is taken from below the foreign 

 substance and placed above it,* thereby adding to the thickness of the 

 upper stratum of the mould and diminishiug the thickness of the 

 portion below the foreign substance. This, within certain limits, may 

 be correct ; but can anyone assert that the decay of the yearly growth 

 of vegetable matter is nil, and that it cannot possibly add its mite, 



^ The Belemnite, which I have stated in my lists as B. semicanaliculatus (non de 

 Blain.) is without doubt the B. Brunsivicensis v. Stromb. During a recent visit to 

 Germany for the purpose of studying the Neocomien strata of that country, I re- 

 ceived much very kind assistance from several geologists, and especially from M. Von 

 Strombeck.— J. W. J. 



2 Geol. Mag. No. 57, Vol. VI. p. 109. 



3 Trans, of the Geol. Soc. 2nd series. Vol. t. p. 505, et seq. 



* Although not actually stated, it seems to be inferred that the soil increases in 

 thickness downwards, the worms burrowing into the subsoil and thereby changmg its 

 nature. This subject will hereafter be referred to. 



