1859.] Mr. Maskelyne on the Crystal Molecule. 95 



WEEKLY EVENING MEETING, 



Friday, April 1, 1859. 



Sir Roderick I. Murchison, D.C.L. F.R.S. Vice-President, 

 in the Chair. 



Nevil Story Maskelyne, Esq. M.A. 



On the Insight hitherto obtained into the Nature of the Crystal 

 Molecule by the instrumentality of Light,* 



The horizon of man's view extends in two directions. The one is 

 turned towards the infinitely vast, and carries his eye into the regions 

 of space, spanning distances that leave his world a speck in creation. The 

 other direction along which he strains his gaze, is into the infinitesimal ; 

 and the microcosm of the crystal is the region it must traverse before 

 it can reach the ultimate units of material consistence, which form the 

 centres of chemical force. That region, however, is to be explored by 

 the reason rather than by the eye, for the minutest thing cognisable 

 by the microscope is left far behind in the first step taken downwards 

 into the crystal world. 



In a crystal there exists a complete regularity of arrangement and 

 of the distribution of its powers of resisting, of transmitting, or of con- 

 verting and modifying any forces that may solicit it. Of this, to a 

 great extent, the external symmetry of its facettes is an expression. 

 But the physical properties of the crystal afford the most perfect 

 evidence of it. 



The different vafieties of symmetry, exhibited by outward crystal- 

 line shape, are found to indicate, with much precision, a correspondingly 



* In this notice a larger space is given to preliminary and other details than 

 could be devoted to them in an hour's discourse. This was felt to be necessary, 

 partly because the speaker entered more on these points than he had intended in 

 the scheme of his discourse ; and having done so it is his wish to give a clear state- 

 ment of them : partly too because the subsequent views for which he is much 

 indebted to the conversations and private letters of his friend Professor Grailich, 

 are more intelligible to a general audience by the help of such preliminaiy expia- 

 tions. He believes they may render a beautiful subject — which must be diflficult, 

 and cannot be popular in the childish sense of the word — suflBciently intelligible, by 

 patient study, to be interesting to persons such as those who did him the honour of 

 forming his audience on the 1st of April. 



