Value of (he Shells of Mollusca. 267 



carefully the question of the value of the shell with these 

 animals, and am satisfied that it is not much overrated, and 

 that it is highly expressive of the intimate nature of the 

 animal, because it is so closely connected with its organic 

 functions. I find that in some species, those portions of the 

 shell which have been regarded only as ornamental in their 

 character, are of much value, because they are connected 

 with the function of the Mantle. 



Professor Silliman alluded to a work of three large volumes, 

 published several years since, upon a single species of Mollusc, 



by Count , in which the author stated his belief of the 



organic connection of the shell as he had first seen it de- 

 posited in crystals. 



Dr Burnett alluded to an analogous fact, of the formation 

 of bird's eggs, as it had been shewn that the shell first ex- 

 isted in the shape of crystals, and these most probably inside 

 the cells, so that the disposition of the inorganic matter was 

 essentially connected with the organic life. — American Asso- 

 ciation/or the Advancement of Science, for 1850. 



On the Structure of the Lunar Surface, and its relation to that 

 of the Earth, By James Nasmyth, Esq. 



The subject was illustrated, in a discourse delivered to 

 the British Association, at Edinburgh, in August 1850, 

 by a series of drawings which the author has executed by 

 the aid of a powerful telescope, which he has made for 

 himself for the express purpose of following up his inves- 

 tigations on the subject in question. These appear, from 

 the drawings exhibited and the description given by Mr 

 Nasmyth, to afford striking illustrations of the nature and 

 action of some of those agencies which in remote periods of 

 the earth's geological history has given to its surface many 

 of its most remarkable features ; namely, as to the causes 

 of volcanic action, the protrusion of igneous rocks, the up- 

 heaving of mountain ranges, as well as the submersion of 

 extensive portions of the earth's surface, all of which vast 

 geological phenomena Mr Nasmyth appears to assign to a 

 few grand and simple prime causes, resulting from the con- 



