570 Correspondence — Prof. T. G. Bonney. 



The principal discrepancy between our results is that the 

 remarkable variety of enstatite, very hard and sometimes of a red- 

 brown colour, which he describes as common in the deposits, 

 is absent from all the collections which I have seen. Staurolite, 

 on the other hand, which he does not mention, is very abundant. 

 It occurs in worn crystals, black or dark brown, and with crystalline 

 faces not good enough for measurement on the reflecting goniometer. 

 The angles, however, agree well with those of staurolite. A curious 

 fact is that no cross twins, so characteristic of this mineral, were 

 observed among the crystals. Seeing that kyanite is so abundant, 

 the presence of staurolite is exactly what might be expected. 

 Mr. Mennell is not disposed to agree with Professor Gregory that 

 the diamonds may have been derived from pegmatites, but the 

 conclusion to which I was led by an inspection of the minerals of 

 the alluvial deposit was that they could have come only from the 

 margin of a granite and a contact aureole. The whole paragenesis 

 indicates this. Not one of the minerals I have seen resembles those 

 of the Kimberley diamond pipes. John S. Flett. 



THE TRIMINGHAM CHALK. 



Sir, — It seems to me also desirable to make a few comments on 

 Mr. Brydone's letter in yt)ur November number. I did not " affect to 

 regard" his note about his use of the magnetic for the true north " as 

 addressed to myself personally." The communication, though it also 

 expressed Mr. Hill's views, was written by myself to save time and 

 trouble. Our remark was not intended as a criticism of anybody, 

 but to explain why we had not altered the terms which we began to 

 employ fourteen years ago, when our attention was concentrated 

 more on the hypothesis advanced in the Geological Survey Memoir 

 than on verbal details. We took those terms from the general 

 direction of the coast, as shown on the Ordnance Survey Map, and 

 I maintain that our practice, the statements in my note (except that 

 the misprint, Weymouth for Wey bourne, escaped correction), and 

 my use of the word ' trend ' are correct. The " trend of a coast " 

 is not "ever varying from point to point and as you take it at the 

 base or top of the cliff," but it expresses, according to Nares, 

 Johnson, Webster, and others, the general direction, especially 

 where there is a bending, of a coast, mountain chain, etc. 



I never asserted the arch in my sketch to be identical with that to 

 which Mr. Brydone referred in his papers. I said " the isolation of 

 the more notable bluff is now complete," and gave a description of 

 what then remained. My sketch and the photograph published by 

 Mr. Hudleston in your November number exhibit the later stages 

 of the work begun in October, 1905. My purpose in stating that 

 a certain mass of chalk was a separate boulder was to imply, not 

 that Mr. Brydone had denied this, but that the fact, under all the 

 circumstances, diminished rather than increased the probability of 

 a neighbouring mass being a seastack. 



