364 C. Davison — British Earthquakes of 1889. 



scientific basis for the hypothesis that the Upper Sands were once 

 as rich in fossils as the more clayey Barton beds of Hampshire. 

 The hypothesis of * decalcification ' may be run too hard. We must 

 be allowed to insist upon proof of the fact being given in any case 

 before admitting it as an explanation. In the case before us we can 

 understand perfectly well how atmospheric waters, charged with 

 the humus acids furnished by the decay of forest-litter in this area 

 of ancient forest-land have first taken up iron in the sands to form 

 salts of the protoxide, and then, on coming into contact with the 

 shells embedded in the sands, have b}'^ a simple chemical reaction or 

 interchange of acids and bases substituted for the carbonate of lime 

 carbonate of iron, to be subsequently broken up by the oxidation 

 of the iron into the peroxide, which gives the pseudomorphic casts 

 of the original shells.' I have not, after much study of the question, 

 the slightest doubt that this is the true history of these ' irony casts ' ; 

 and I think that the direct action of merely carbonated atmospheric 

 waters has had very little to do with their production. 



In connexion with these Upper Sands space prevents me from 

 adding more than to draw attention to the fact that there are I 

 believe signs in places of their beds having been formed by the 

 planing down of the sand-dunes of the earlier deltaic stage ; the 

 materials having been stored up to a large extent during the long 

 period occupied by that stage, and 011I3' needing redistribution by 

 tidal action to give us in part the present beds of the Upper Sands. 



The time represented by these few hundred feet of strata, as 

 measured by the maximum development of their continental equiva- 

 lents, is seen to be very great ; and the study of their physical 

 history tells us that such a lengthened period of time was required 

 for their formation. The two series of deltaic clay deposits (entirely 

 tinfossiliferous), with their intervening and intimately associated 

 green earths, probably occupied by far the greater portion of it. 

 Compared with the necessarily slow accumulation of materials which 

 the physical study of these reveals to us, the deposition of the fluvia- 

 tile sands which preceded them and of the marine-estuarine sands 

 which succeeded them was probably what might almost be called 

 a rapid process. 



V. — On the British Earthquakes of 1889.^ 



By Charles Davison, M.A., 



Mathematical Master at King Edward's High School, Birmingham. 



{Continued from page 316.) 



(PLATE X.2) 



3. Ben Nevis Earthquake : May 22, 1889. 



Time of occurrence, 13 h. 58 m. ; Intensity, about IV. Epicentrum, 



probably not far from Ben Nevis. 



1 There is nothing new in this. Dr. Alexis A. Julien explained in this way the 

 formation of the irony casts in the " Northampton Sands," which are well known. 

 See "Amer. Assoc. Adv. Sci." for 1879. 



^ Plate X. illustrates the area disturbed by the Lancashire Earthquake of February 

 10th, 1889, described in the Geological Magazine for July, 1891, pp. 306-316, 

 forming part 2 of this communication. 



