568 Correspondence — H. J. Lowe. 



specimens of pyrites in collections was discussed. Calcite, a clear 

 scalenohedral crystal, probably from Iceland, consists of a combination 

 of the two scalenobedra (201) and (12.0.7), both largely developed, 

 and with an angle of 4^ degrees between corresponding faces. 

 Epidote, a crystal, probably from Ala, Piedmont, closely resembling 

 in appearance the yellow prismatic crystals of anatase, carries a minute 

 face (134) (Dana's orientation) in addition to twenty other crystal- 

 forms. 



Dr. G. F. Herbert Smith: "A Curious Crystal from the Binnen- 

 tal." The crystal, which was found with a few loose sartorite 

 crystals in the Trechmann Collection, is twinned and tabular in habit, 

 and shows signs of corrosion. The symmetry is peculiar, since, 

 although a face occurs at right angles to the prism edge, it is neither 

 a plane nor a pole of symmetry, and the crystal appears to represent 

 a new species of sulpharsenite. 



CORRESPO]SrDE]SrCE. 



THE TEETIARY GEOLOGY OF DEVON AND CORNWALL. 



Sir, — Referring to your reviewer's remarks in the November 

 number, p. 521, on an inquiry into the recent views relative to 

 " The Tertiary Geology of Devon and Cornwall", may I be allowed 

 a few lines to meet the objections that the " argument concerning 

 the age of the limestone caverns is not veiy clear, and its bearing on 

 the point at issue is not obvious ". 



The point at issue is the submergence of the peninsula during the 

 Pliocene era as predicated by the platform theory. Of the seven 

 standpoints from which the theory was considered, the caverns were 

 taken as one contributing important controverting evidence. It 

 was shown that caverns are almost entirely formed by solution of 

 the rock, an immeasurably slow process, requiring geological ages to 

 form these large subterranean hollows. It was also pointed out 

 that the lowest deposits in the Devon caverns are glacial formations 

 (surface material swept through the swallow-holes into the lowest 

 depths during extraordinary climatic conditions) that determine the 

 pre-Glacial existence of the cavern. It follows that the human and 

 animal relics found in this deposit (the breccia) must have been of 

 Pliocene origin. Now as the elevation of the caverns above the 

 sea-level during their whole existence is unquestioned, and when 

 the many ages taken in the formation of the similar Derby and 

 Yorkshire caverns are put in comparison, it does not appear 

 consistent with the character of the facts to assign the formation of 

 the Devon caverns to the comparatively short geological period that 

 must be implied to terminate the Pliocene era, as subsequent to the 

 vast space of time drawn upon that era, which the enormous results 

 embraced by the platform theory demand. 



I submit the cavern phase of the argument to be one that is 

 relevant, cogent, and obvious. 



H. J. Lowk. 



Torquay. 



