124 i-KOLU(fi. 



ON THE MARINE SHELLS 



IN THE 



BLASHENWELL DEPOSIT. 



[ Read at St. Aldhelm's Head, July 2nd, 1857. ] 



As it is often difficult to arrive at a correct understanding of 

 the original causes which have produced phgenomena existing at 

 the present time, and since different individuals will consequently 

 view them in different lights, and form upon them different 

 opinions, it becomes advisable that those who have severally 

 given their attention to any one object, but whose opinions are 

 not in unison, should individually lay them before the society, 

 not as antagonistic to each other, but simply aiming towards 

 the same point, namely, a satisfactory result of their labours. 

 With this desire then, and as Mr. Mansel, in his " paper upon 

 the Blashenwell Deposit," has done me the honour of referring to 

 my opinion in conjunction with that of a gentleman who ranks 

 amongst the first of the Members of the " Geological Survey," 

 I think, that without incurring the risk of being deemed uncour- 

 teous to him, I may state that opinion fully, although in some 

 points it differs from his. I completely agree with Mr. Mansel 

 in respect of the origin of this deposit, namely, its being com- 

 posed of tufa and travertine, precipitated by the Blashenwell 

 spring ; whether in form of a lake, or pond, or merely as flowing 

 over a limited space, is imimportant. I am however induced to 

 conceive, that the space must have been constantly covered, 

 although probably at times, only by shallow water, from the 



