Scientific Meeting in Germany. 285 



on the causes of the formation of different combinations of crys- 

 tals in the same species of mineral. On this subject, he observed, 

 our knowledge was exceedingly scanty. We had scarcely a single 

 observation or inquiry to which we were able to refer. Experi- 

 ment alone presented us with facts by the aid of which we might 

 possibly make some progress. It was a familar fact that when an 

 ea-ily soluble salt (alum) crystallised from a pure solution, the 

 forms exhibited differed from those which were obtained from im- 

 pure solutions. This fact was sufficient of itself to show beyond 

 a doubt that the medium in which substances crystallise exerts an 

 influence upon the form of the crystal. Taking this for our prin- 

 ciple, and applying it to nature, we find it to be a fact that certain 

 minerals, when they occur in certain rocks, appear under one and 

 the same form of crystal — when magnetic iron ore, for example, 

 occurred in chlorite-schist, it was found in the general case to oc- 

 cur in the form of an octohedron. The subject was worthy of 

 careful investigation, and might turn cut to be of very great im- 

 portance in a geognostic point of view. 



At the sitting of Tuesday (September the 22nd), Professor Dau- 

 bree, of Strasburg, spoke on the formation of sulphuret of copper 

 and apophyllite from the thermal springs of Plombieres. In the 

 course of certain excavations, undertaken with the purpose of 

 fencing in these springs, the speaker had found two recent sub- 

 stances, which were of geological interest from the resemblance 

 they bore to certain minerals. On a bronze cock, of Roman work- 

 manship, which had been lying amidst the rubbish of ancient 

 buildings for more than fifteen centuries, sulphuret of copper had 

 been formed in the shape of beautiful crystals. They belonged to 

 the hexagonal system, and could not be distinguished from natu- 

 ral crystals. From a similar composition, artificial crystals be- 

 longing to the regular system had already been obtained. The 

 circumstances under which they had been formed seemed to dif- 

 fer from those under which the formation of similar crystals occur- 

 red in veins. The ancient mortar into which the warm water 

 percolates includes in its cavities colourless crystals identical in 

 form and composition with apophyllite. They owe their formation 

 to the operation of the silicate of potash from the hot springs on 

 the lime of the mortar. The formation both of the apophyllite 

 and of the hexagonal sulphuret of copper had here taken place in 

 water of which the temperature did not exceed 70 deg. C. 



Dr. Volger gave an account of the result of his observations on 

 the phenomena of earthquakes in Switzerland, and especially the 



