501 
MEETING OF SAYANS AT SPEYER. 
By H. C. SoRBY, E.R.S. 
Having been present at the meeting of German naturalists (Yer- 
sammlung deutscher Naturfoi^cher 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 diflferent 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 j 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 
