48 Prof. W. H. Miller on the Form of an Alloy of Bismuth. 



character, we come to the conclusion that these slaty masses 

 have been subjected to enormous pressure, and by the sure 

 method of experiment we have shown — and this is the only 

 really new point which has been brought before you — how 

 the pressure is sufficient to produce the cleavage. Expand- 

 ing our field of view, we find the self-same law, whose foot- 

 steps we trace amid the crags of Wales and Cumberland, 

 stretching its ubiquitous fingers into the domain of the pastry- 

 cook and ironfounder; nay, a wheel cannot roll over the half- 

 dried mud of our streets without revealing to us more or less of 

 the features of this law. I would say, in conclusion, that the 

 spirit in which this problem has been attacked by geologists, 

 indicates the dawning of a new day for their science. The 

 great intellects who have laboured at geology, and who have 

 raised it to its present pitch of grandeur, were compelled to 

 deal with the subject in mass ; they had no time to look after 

 details. But the desire for more exact knowledge is increasing ; 

 facts are flowing in, which, while they leave untouched the 

 intrinsic wonders of geology, are gradually supplanting by solid 

 truths the uncertain speculations which beset the subject in its 

 infancy. Geologists now aim to imitate, as far as possible, 

 the conditions of nature, and to produce her results ; they are 

 approaching more and more to the domain of physics, and I 

 trust the day will soon come when we shall interlace our friendly 

 arms across the common boundary of our sciences, and pursue 

 our respective tasks in a spirit of mutual helpfulness, encourage- 

 ment and goodwill. 



V. On the Form of an Alloy of Bismuth. By W, K. Miller, 

 M.A.y F.R.S., F.G.S., Professor of Mineralogy in the Univer- 

 sity of Cambridge ; with an Analysis of the Alloy , by Allan 

 Dick, Esq.^ Metallurgical Laboratory y School of Mine^. 



THE specimen was obtained by Dr. Percy from Mr. Pers- 

 house of Birmingham. 

 The crystals belong to the prismatic system. The symbols 

 of their simple forms are — c, 001 ; r. 111. 



ITie angles between normals to their faces are, — 



re 60 17 

 rr' 61 38 

 rr'' 89 4 



Communicated by the Author. 



