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MEETING OF SAVANS AT SPEYER. 

 By H. C. Sorby, F.R.S. 



Having been present at the meeting of German naturalists (Ver- 

 sammlung deutscher Naturforscher und Aerzte) held at Speyer in the 

 middle of last September, I thought that probably a short account 

 of such papers as were more or less closely connected with geology 

 might interest some of your readers. On the whole, the meeting is 

 analogous to our British Association, the various branches of science 

 being divided into nine different sections ; but a larger number of 

 miscellaneous subjects are brought before the general meetings. I 

 confined myself entirely to the section for mineralogy and geology, at 

 which, however, no very great number of papers were read. 



In opening the proceedings, the president for the first day, Dr. 

 Noggerath, gave an account of M. Daubree's experiments in connexion 

 with the theory of volcanos, described in the May number of the 

 " Geologist" for this year, p. 195, and expressed doubts as to whether 

 with an indefinitely greater thickness of rock than that used in the 

 experiments the tension of the steam would be indefinitely increased. 

 M. Daubree, on his arrival a day or two after, admitted to me that 

 this doubt had already occurred to him, and said he intended to clear 

 it up by experiment. 



Professor Blum, whose investigations and writings on pseudomorphs 

 are so well known, read a paper on the question whether certain 

 examples are really due to alteration, or whether, as argued by M. 

 Delesse, they are merely crystals of a foreign substance enclosed in an 

 unaltered crystal. He exhibited a very excellent series of specimens, 

 which I had previously carefully examined with him at Heidelberg, 

 and they appeared to me to completely establish his own views with 

 reference to those particular cases. After this the president said that 

 the subject of pseudomorphs had been brought before the members of 

 the section, but perhaps they did not know that a manufacturer of 

 pseudomorphs was present amongst them, and called on me to exhibit 

 and describe the specimens I had with me. I said that in my experi- 

 ments I had endeavoured to accomplish my purpose rather by length 

 of time than by a very high temperature. In some cases I had kept 

 crystals of various minerals in the appropriate solutions for many 

 months, at the ordinary temperature ; and for other pseudomorphs 

 had enclosed the crystals in tubes of glass or brass and kept them for 

 some weeks or months in the boiler of a steam engine at a heat of 

 about 145° C. (293° F.). In this manner I had succeeded in making a 

 considerable number of pseudomorphs, similar to those met with in 

 nature ; the only striking difference being that often the manufactured 

 specimens are of smaller grain, and have sharper angles. Amongst 

 them are carbonate of lime in the form of gypsum, of fluor-spar, and 



