Scientific Intelligence--^Geology and Hydrography. STl 



angle than 37°, because it is under this angle alone that it is com- 

 pletely polarized ; but under angles of 10° or 12° greater or less 

 than 37°, the number of polarized rays which the tourmaline can 

 arrest is still so considerable, that the same means of observation 

 cannot fail to be attended with very advantageous results. 

 Poggendorf proposes to use for this important purpose, in- 

 stead of the tourmaline, NicoPs Cole Spar Prism, because, from 

 its being colourless, it is much better fitted for the purpose. 

 By engaging in such experiments, " mariners,*" Arago remarks, 

 '* will throw a hght on a curious question of photometry : they 

 will probably confer on navigation a means of observation which 

 may prevent many shipwrecks ; and by introducing polarization 

 into the nautical art, they will afford an additional proof of what 

 those individuals expose themselves to who unceasingly collect 

 experiments and theories without any practical application of 

 them, meeting every remonstrance with a contemptuous cui 

 honor Ere long, we doubt not, ships generally, at least all 

 those vessels specially occupied in geographical and hydrogra- 

 phical researches, will before leaving port be provided with 

 Nicol's valuable little instrument. 



4. Thermal Springs in the Columbia Territory. — In a let- 

 ter to Professor Jameson from Dr Gardiner, dated 18th Sep- 

 tember 1835, is the following notice :— ** I have ascertain- 

 ed the existence of three more thermal springs in the Columbia 

 territory, in addition to those I formerly noticed.* Specimens 

 of the water of these have been sent to me ; one only have I 

 been able to analyze ; but the quantity of water was too small 

 to enable me to determine the numerical proportions of the in- 

 gredients. These were carbonic acid in large quantity, carbo- 

 nates of lime and magnesia, muriate and sulphate of soda, and 

 silica ; the total amount of solid matter was = 26,0 in 10,000 

 parts of water. Its specific gravity was 1007.1. — The silica 

 was in l^rge quantity. It is situated on Bear River, which dis- 

 charges itself into Great Salt Lake, in the desert between Snake 

 River tmd Mexico, and is in the midst of a country from which 

 I have specimens of obsidian and pumice. You may readily 



• Ed. PhiL Jour. vol. xr. p. 206. 



