Intelligence and Miscellaneous Articles. 3.23 



on the other, and the vapour acts in a similar manner, so that only 

 one side at the same time is affected by each. 



Your obedient servant, 



Thomas Woods. 

 Parsonstown, February 1863. 



ON SOME SPECIMENS OF PSEUDOMORPHS IN THE IMPERIAL 

 MUSEUM OP VIENNA*. BY DR. TSCHERMAK. 



The Imperial Museum of Vienna contains many very curious 

 specimens of Pseudomorphs, and among them are several calculated 

 to throw light on controverted geological questions. In a hand- 

 specimen of gneiss from the Rathhaus-Berg, near Gastein, amphi- 

 bole has replaced mica. This gneiss contains altered amphibole in 

 the interior of masses of mica ; and it may therefore be inferred, 

 with a certain degree of probability, that the whole of this gneiss, 

 whose felspathic components likewise bear traces of metamorphism, 

 is an altered amphibolic rock. The same, so far as may be inferred 

 from cabinet- specimens, may be the case with other varieties of 

 gneiss, especially with those of Brazil. 



Pseudomorphs of compact felspar, replacing crystals of the same 

 mineral species, occur in the antique green porphyry of Italy and 

 Egypt, as also in the diabasic porphyry from the Hartz, — a fact 

 not unimportant in regard to the origin of certain varieties of this 

 group of rocks. A double Pseudomorph — crystallized gypsum meta- 

 morphosed into fibrous gypsum, and this, in the course of time, into 

 fibrous quartz — occurring, together with spaces left by the decom- 

 position of crystallized iron pyrites, in a specimen of chloritic argil- 

 laceous slate from the Eifel, may suggest some of the processes 

 undergone by this rock before it arrived at its present condition. 

 Some other cases of Pseudomorphs, as specular oxide of iron re- 

 placing olivine in the trappean rocks around Edinburgh ; opal re- 

 placing nephrite, from Elbingerode ; opal replacing augite, from the 

 same locality ; and calcareous spar having taken the place of augite 

 in the metamorphosed pyroxenic porphyry of Tokoro (Transylvania), 

 have been neither noticed nor described before. — Proc. Imp. Acad. 

 Vienna, November 6, 1862. 



NOTES ON THE OLD EGYPTIAN AND GREGORIAN CALENDARS. 

 BY S. M. DRACH, P.R.A.S. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



In Schubert's Reise in das Morgenland (vol. ii. p. 179) the author 



states that the Egyptians made 309 synodical months equal to 25 



years of 365 days, equivalent to a month of '29 d 12 h 44 ro 16 s -3107. 



With the hitherto accepted secular acceleration of Laplace ( Vince, 



* Communicated by Count Marschall. 



