Geology and Natural History. . 401 
-considered as made up of a superficial portion of changeable tem- 
perature and a profound portion of constant temperature. As to 
the probable temperature of the latter tpi the author in con- 
‘sidering the upper regions from which th e descends concludes 
higher altitudes of temperatures, nage p> Oi , —1°, —2°, —3° 
and so on; the final diagram given shows these ’ successive layers 
divided by horizontal lines (taking in seisiheras the effect of 
the earth’s interior heat) which the author euggeste as the ceri 
ble distribution of the interior temperature of the ice-mass, and he 
concludes with the hope Sea the my of his theoretical deduc- 
tions may be tested by experimen 
6. ys ch of the Rated ine of Lake Lahontan, by 
Israzt C, Russert.—From the third Annual Report of the 
ange of the U. 8. Geological Survey. Rola important memoir, 
now issued as a separate paper, has been ced in the preceding 
volume of this Journal (p. 67). It is diestrated by a te en- 
graved plates, and two fine heliotype plates, one of a remarkable 
group of the crystals of the pseudomorph named by King 
* thinolite.” 
7. Geologische Briefe aus America ate Eecellenz Herr 
HI. v 
Dr, H. von Dechen.—These letters by the German mineralogiet, 
Professor vom ae contain some of the results of his observa- 
ions d ent journey, extending over about a year, 
through the United States and Me ico. . T arked b 
the same keenness of observation and vividness of description 
which characterize the writings of the same author from Sicily, 
Syria, Palestine and other countries. ome of the localities 
spoken of in the letters are Colorado, especially the region about 
Pike’s Peak, Virginia City and Nevada, the Yellowstone Park, 
and Mexico, peer Pachuea, Cordova, Zacatecas and Guana- 
xuato. When in Mexico beet ascended nearly to the summit of 
Popocatepetl aA the account of this trip is full of interest; he 
also visited the locality at which tridymite was first fo und in 
Mexico by Castillo, and gives some valuable notes eas i: A 
list is given, with explanatory remarks, of the many fine and rare 
mune found in the neighborho ood of Guanaxuato. 
the Composition of Herderite ; by J. B. aauepouae 
(Compania in a letter dated Oct. 14.) —In regard t 
question as to whether the loss on the ignition of herderite is oa 
as * clawed by Winkler ee net number), to the oe of 
of fluorine, it being corlant re oxygen.  Athesa I have not 
8 
