Scientific Intelligence. '^Hydrography. 891 



appears from this that a different height may be obtained for 

 each season and each hour of the day. The author does not 

 venture to offer an opinion respecting the causes of this anomaly, 

 but he thinks that there is wanting a series of such observations, 

 sufficient to enable us to discover the causes of these differences, 

 as well as that of the co-efficients of the heights in our barome- 

 trical formula?, and of the corrections rendered necessary by the 

 changes of temperature. The correction necessary for the heat 

 in a vertical direction, is exactly 97 toises for i degree of Reau- 

 mur, bv the sulnmer observations. The winter observations are 

 of no use in this respect, on account of the southerly winds 

 which prevail at these heights at that season. The daily oscil- 

 lations of the barometer which, according to fourteen observa- 

 tions made daily at Zurich, appear very regular, cease entirely 

 to exist at the summit of Rigi. — Btblioth. Univers. Dec, 1827. 



HYDROGRAPHY. 



7. Blowing a River out, — The southern mail failed at 

 Washington on Tuesday last, in consequence of the gale, which 

 was so long and so violent, as to blow the waters out of the 

 Potomac to such a degree as to render it unnavigable. — New 

 York Paper ^ 



8. Chemical Researches respecting the Mineral Waters of 

 Geilnau, Fachingen, and Setters. By G. Bischof. 8vo. Bonn, 

 1826. — Professor Bischof 's interesting work on springs, entitled 

 " Chemische Untersuchungen,'^ &c. contains much curious and 

 valuable information. The first chapter contains the analysis 

 of three springs, and the second their geognostical relations. 

 They issue from clayslate, and are in the vicinity of dolomites 

 and igneous rocks. In the third chapter, the author treats of 

 the relation of the composition and temperature of the springs to 

 the surrounding rocks. The springs that are strongly impreg- 

 nated with carbonic acid, and contain soda, are connected with 

 the volcanic lines. They are scattered in seven volcanic groups, 

 from the Eiffel to the Riesengebirge. He enumerates these 

 groups, and connects with them the Pyrenees, Auvergne, and 

 the Vivarais. In Switzerland, on account of the absence of ba- 

 salt, there are none of these springs. The soda is furnished by 

 the volcanic rocks. As all the springs contain more or less car- 



