144 Correspondence — Col. George Greenivood. 



beach; for even a robust bermit could not have long supported 

 life with the roaring waters rushing through the channel, locally 

 known as Hell Gate, within a few feet of him, and effectually cutting 

 him off from the mainland, even though this channel must then have 

 been considerably wider than at present. 



Dr. Martin Bull, of St. Helier's, informs me that at least two other 

 raised beaches occur in the island. One of these is at the southern 

 end of St. Owen's Bay, near La Pulente ; it is about 100ft. above 

 the present beach, and contains quantities of shells of extant species. 

 The other is in St. Clement's Bay, between Le Hoeq and Pontac. 



Proofs of elevation are not confined to Jersey. A similar raised 

 beach is passed in mounting from the Harbour of Sark by the side 

 of the road leading into the interior of that islet. 



Downing College, Cambridge, T. W . Danby. 



January 25, 1876. 



Glacial Erosion. — The subjoined Postscript deserves a place in 

 this Magazine, although the hand that penned it is now cold. It 

 was sent too late as a rider to a letter which we published in October 

 last (p. 524).— Edit. Geol. Mag. 



P.S. — Follow Swaledale, Wensleydale, and all the rivers descending 

 from the Pennine chain, through the soft strata, between the Permian 

 and the hard gorge cut by the Humber through the Chalk Wolds. In 

 these soft strata the separate valleys almost disappear. Atmospheric 

 disintegration, and the vertical descent and erosion of rain, have 

 worn down the hills which intervened into what is called " The 

 Plain of York." But if, as Mr. Goodchild says, valleys are formed 

 and widened by "mechanical means," be these mechanical means the 

 horizontal thrust of glaciers or the horizontal undermining of rivers, 

 each valley would run between two precipitous cliffs, and the Ouse 

 and the Humber, and their tributaries should traverse what is now 

 the Plain of York, with sides as high as the Chalk Wolds, and running 

 up to Mr. Goodchild's " scars " and ledges on the Pennine Chain. 



Brookwood Park, Alresford. Geokge Gkeenwood, Colonel. 

 September 2ith, 1875. 



Aquarium Rockwork. — The rockwork in the tanks at the New 

 Westminster Aquarium contains a considerable amount of Portland 

 Oolite. We understand that it was purchased from the debris of the 

 Colosseum, Eegent's Park, as a sandstone, and it appears to have 

 been introduced into salt and fresh-water tanks alike without in- 

 vestigation as to how far it is suitable. It perhaps may do no harm, 

 but it would be well if any one who has experience of what its effect 

 will be, would communicate his knowledge before any animals are 

 placed in the tanks. There is, in addition, a good supply of Carbon- 

 iferous Limestone used, and in considering the conditions, it must be 

 remembered that the water circulates constantly from tank to tank, 

 so that the carbonate of lime will be just as present to all the inhabi- 

 tants of the aquarium as to the Lamellibranchs and others it might 

 (possibly ?) benefit. — Nature. 



