Notices of Memoirs — Mineralogy. 267 



grew immediately on the tin ground in Carnon and Pentuan, and 

 during the forest epoch, therefore, the tin ground could have been 

 worked at surface. Unless the premises were wholly incorrect, tin 

 must have been an object of search in Cornwall when the now sub- 

 merged portions of these ancient forests had not disappeared wholly 

 beneath the waves. When was this ? The positive evidence was 

 small. The Mammoth existed during part of the forest period, but the 

 submergence was so gradual that it was not absolutely needful to hold 

 that there were miners contemporaneous with the Mammoth. But 

 there was some valuable negative evidence in the fact that the level 

 of England could be proved to have remained unaltered since the days 

 of the Eoman occupation. The fact, too, that St. Michael's Mount 

 still answered to the description of the Iktis of Diodorus Sicuhis, 

 was another proof that the subsidence of the forests and the accumu- 

 lation of the bulk of the overlying deposits must have occurred 

 long before. The general conclusions tended to show : that the 

 historical evidence of the antiquity of Western mining carried it 

 back at least 2,300 years ; that the inferential evidence nearly, if not 

 quite, doubled that period ; that the geological evidence antedated 

 its commencement to a time when the Mammoth either still existed 

 or had not long disappeared, and when the general level of Cornwall 

 and Devon was at least 20 to 30 feet higher than it was at present. 



in. — Brief Abstracts — A. Mineralogy. 

 1. — On Pseudomorphs of Eock-salt from Westeregeln. Uber 

 Steinsalz-Pseudomorphosen von Westeregeln. Von Herrn E. 

 Weiss, in Berlin. Zeitschrift d. Deutschen Geologischen Gesell- 

 schaft. Band xxv. 1873, Heft 3, pp. 552-561. 



TWO shafts sunk for working rock-salt near Westeregeln, N.W. 

 of Stassfurt, in Prussian Saxony, have yielded the pseudo- 

 morphs described in this paper. A collection of specimens of the 

 various rocks pierced by the shafts has been presented by Mr. 

 Douglas, of Westeregeln, to the Mining Academy of Berlin, and 

 it is on these specimens that the present communication is founded. 

 The pseudomorphs are of two distinct kinds : the one a pseudomorph 

 of rock-salt after rock-salt, the other of rock-salt after carnallite. 

 A section of Shaft I. shows that the crystals were found chiefly in 

 beds of saliferous clay' at a depth of about 125 meters from the surface. 

 The pseudomorphs after rock-salt present the appearance of small 

 white, yellow, or pale-red cubes, more or less distorted or elongated, 

 and frequently with oblique angles, so as to resemble rhombohedra. 

 However irregular the angles, the crystals may always be readily 

 cleaved into laminae in three rectangular directions, representing the 

 ordinary cubic cleavage of rock-salt. The external surface of the 

 pseudomorphs is formed by a very thin layer of quartz which remains 

 behind, as a hollow shell, when the salt is removed by solution. 

 The history of these pseudomorphs is thus interpreted by the author : 

 the salt originally crystallized in the form of true cubes scattered 

 through a matrix of soft clay ; these crystals were then dissolved out, 

 leaving cubic cavities which were afterwards distorted either by 



