Chalk-Formation. 63 



in the north of Germany. He has, moreover, found the Wealden forma- 

 tion near Bottingen in the High Alps. 



Chalk- Formation. — In extension of our knowledge of the chalk-forma- 

 tion, the Rev. J. Gunn has sent us a short communication, accompanied 

 by a lithograph representing the columnar disposition of some Parainou- 

 dras, to the height of many feet, one above another, in the chalk of Nor- 

 folk. The history of these enormous urn-shaped flints, •which were first 

 noticed by Professor Buckland in an early volume of our Transactions, 

 first series, vol. iv., p. 413, pi. 24, is still involved in much obscurity. 

 Their form is most probably due to siliceous matter collected around, and 

 penetrating throughout, the substance of gigantic spongiform bodies ; but 

 we have j'et to learn the reason why they are occasionally placed in single 

 vertical rows, almost like the joints of a basaltic column, sometimes nearly 

 touching, but not articulating with, one another. 



A paper has been read by Mr Henry Plawes Long on the occurrence of 

 numerous subterraneous chasms or swallow-holes in the chalk on the west 

 of Farnham, with observations on the drainage of the country near the 

 west extremity of the highly-inclined ridge of chalk called the Hog's 

 Back, between Guildford to Farnham. The land-springs immediately on 

 the north of Farnham descend southwards in open gulleys over tertiary 

 strata, until they arrive at the narrow band of chalk which passes under 

 Farnham Park, where they arc suddenly engulfed in transverse fissures 

 or swallow-holes, through which they pass under ground to a consider- 

 able distance, and again break forth on the southern side of the chalk. 

 Seven of these swallow-holes occur near Farnham, from some of which 

 the water emerges in sufficient force to turn a mill. They are probably 

 connected with subterranean faults and transverse fractures, the origin of 

 which was coeval with the elevation of the narrow band of chalk which 

 forms the Hog's Back, and which, near Farnham, is inclined at a high 

 angle to the north. The water that now passes through the Farnham 

 swallow-holes may tend to enlarge the chasms through which it takes its 

 subterraneous course, by dissolving slowly the chalk of their sides in the 

 small quantities of carbonic acid which rain-water usually contains. 



Similar transverse fractures, on a greater scale, have given origin to the 

 chasms, which, being enlarged by denudation into transverse valleys, af- 

 ford outlets through the high escarpment of the chalk to the rivers that, 

 rising within the Weald, flow through the escarpment of the North Downs 

 into the valley of the Thames, and through the escarpment of the South 

 Downs into the sea, viz. to the Wcy, the Mole, thoDarent, the Medwav, 

 and the StOUT, through chasms in the North Downs ; and to the Arun, the 

 Aduz, the Oumj, and the Cuckmcre, through chasms in the South Downs. 



Dr Mitchell has communicated a paper on Artesian and other wells, in 

 the gravel and London clay in Ks.sex, shewing that water occurs under 

 the London clay at various depths, the deepest at Foulness Island I 

 400 feet. He attributes this inequality in part to unevenness in the sur- 

 face of the subjacent chalk. On reaching the chalk a large volume of 



