Correspondence — A. H. Hunt. 331 



Museum. The specimen has since been sent to London for examination, 

 and casts were made for the British Museum and for Jermyn Street, 

 as it was felt that the specimen might become of importance in future 

 discussion. Bennett was positive in his assertion that the material on 

 the stone heap came from Ladock Quarry, but Mr. J. O. Clemmow, of 

 Ladock, who has been at some trouble in the matter, writes me as 

 follows, under date 30th May, 1908 : — " As a large quantity of stone 

 ftom the South. Coast, near the Helford lliver, has been brought into 

 the immediate neighbourhood and broken for the roads, I should say 

 that considerable doubt exists as to where the stone which produced 

 this fossil was quarried." 



The fossil seems to me to be the internal cast of a species of Spirifer 

 of Taunusian age, and its appearance is suggestive of some southern 

 locality, possibly the Looe area, and certainly not such, as one would 

 expect from the Ladock stone. A shai'p look-out is now being kept 

 for any trace of life from the Ladock Quarry, but the men working it 

 have never seen a single shell. Nor has any sign of life ever been 

 seen by either Mr. Uptield Green or mj^self in numerous visits, except 

 some black flat grass-like markings, which. Mr. I^ewell Arber would 

 not venture even to call 'plant-remains.' 



As the occurrence of this fossil has been so definitely given in 

 print, it seemed worth while to investigate the story while those 

 concerned in the statement were accessible, as endless trouble is 

 occasioned by these records in after years when it is impossible either 

 to prove or dispi'ove them. C. Davies Sherborn. 



A NOTE OX GRANITE AND A NOTE ON RIPPLEMARK. 



Sir, — Since the appearance of my letter on granite in the March 

 number of the Magazine, I have submitted to a physicist the drawings 

 of inclusions in two Dartmoor rocks, which appeared in my paper in 

 the Magazine in March, 1904. (Copies enclosed.) I sought to 

 ascertain the significance of their disproportionate contents of chlorides 

 and of water. This is the reply : — 



"At the temperature when the water, with salt, etc., is above its 

 critical point, the salt and water vapour would form a homogeneous 

 mixture, and enclosures of this homogeneous mixture should show on 

 cooling the same proportions of dissolved salt, crystallized salt, and 

 liquid water." 



The inference is that the enclosures referred to caught up their 

 contents when the temperature was under the critical point of the salt 

 and water, Avliatever that may exactly be. It would be higher, I am 

 told, than that of plain Avater. 



Prom the above it would appear that the chlorides of the western 

 granites are as good records of the temperature of crystallisation as 

 the carbonic acid inclusions of some other rocks. 



To turn to a totally difi'erent subject, I should like to point out 

 that in the paper by the late Dr. Sorby, just published in the Q.J.G.S., 

 an incidental remark will clear up nearly sixty years of uncertaintj'. 

 Dr. Sorby mentions that the depth of water in which he observed the 



