295 



also by all other causes tending to the more rapid communication of 

 heat. This is still more apparent when the coloured rings are formed 

 in a thin plate of water interposed between the lenses, and where the 

 effects are independent of radiation. 



6. " Analysis of the Moira Brine Spring near Ashby-de-la-Zouch, 

 Leicestershire, with Researches on the Extraction of Bromine." By 

 Andrew Ure, M.D., F.R.S. 



The water derived from the spring in question is raised by means 

 of a pump from the coal mines in the neighbourhood of Ashby-de-la- 

 Zouch, is much used as medicinal baths, and is also administered 

 internally, principally as a remedy for bronchocele and scrofulous 

 tumors. The result of the analysis made by the author, is that it 



contains per gallon, grs. 



Bromide of sodium and magnesium 8" 



Chloride of calcium 851*2 



magnesium 16* 



sodium 3700-5 



Protoxide of iron, a trace 



Solid contents 4575"7 



After removing from the water the deliquescent chlorides of lime 

 and magnesia by the addition of carbonate of soda, he transmits 

 through the mother liquor, consisting of chloride and bromide of 

 sodium, a current of chlorine gas, till it communicates the maximum 

 golden tint, and then adds sulphuric sether, which, by agitation, car- 

 ries with it to the surface the bromine and chlorine, constituting a 

 -eddish yellow stratum. The proportion in which these two elements 

 exist in the evaporated solution may be ascertained with the greatest 

 nicety by the addition of a solution of nitrate of silver ; the method of 

 calculation for this purpose being detailed by the author. 



7. " On the Nature and Origin of the Aurora Borealis." By the 

 Rev. George Fisher, M.A., F.R.S. 



The author deduces from his own observations made during a re- 

 sidence of two winters in high northern latitudes, taken in con- 

 junction with the concurring testimony of various navigators and tra- 

 vellers, the general fact that the Aurora Borealis is developed chiefly 

 at the edge of the Frozen Sea, or wherever there is a vast accumu- 

 lation of ice • and he conceives that it is produced in situations where 

 the vapours of a humid atmosphere are undergoing rapid congelation. 

 Under these circumstances, when viewed from a distance, it is seen 

 fringing the upper border of the dark clouds, termed the " sea blink," 

 which collect over these places ; and it generally forms an arch a 

 few degrees above the horizon, shooting out vertical columns of pale 

 yellow light. He concludes that the Aurora Borealis is an electrical 

 phenomenon, arising from the positive electricity of the atmosphere, 

 developed by the rapid condensation of the vapour in the act of 

 freezing, and the induced negative electricity of the surrounding 

 portions of the atmosphere 3 and that it is the immediate consequence 



