48 



EEPOET 1873. 



If the crystalline system is not regular, as in case of sulphur, the density must be 

 diiferent in the direction of three axes, and may be calculated by the proportion, 



"■■^'■■M-ff ■■&■■&)'■ 



a, /3, y being the indices of refraction, d^, dr., dj the densities in the direction of the 

 optical axis. 



Table of Indices of Refraction of Elements. 



Observed. Calculated 



Phosi^horus .... 

 Sulphur 



Diamond 



Graphite 



Silicium diamonds 



Boron diamonds 



Mercury 



Silver . . 

 Gold . . 

 Copper 



Zinc .... 



2-1059 



2-22145 



2-115 



2-460G2 



2-51125 



2-04 



2-44 



3-736 



As Carbon- 

 diamond 

 ( TFokler). 



' \ 



6868 



J 5-8 

 ] 4-953 



2-5265 

 30645 I 

 2-8950 f 



2-1365 

 21404 



2-5620 



2-2776 



3-6000 



2-5140 



5-29645 



3-6627 

 4-9450 

 2-6414 



2-7833 



Angle of Pol. Max. 



Observed, i Calculated 



07 36 



03 45 



168 1) 

 j 67 30 f 



05 56 



79 18-5 

 74 49 



G8 24 ' 

 71 51 



64 55 



64 57 



68 40 

 66 13 



79 26 



74 43 



78 34 



69 16 



70 14 



Heat. 



I^ote on a Condition affecting the Splieroidal State of Liquids, and its probable 

 effect on certain Boiler-Explosions. By W. F. Barrett. 



On the General Oceanic TJiermal Circulation. 

 By William B. Carpenter, 3I.D., LL.D., F.R.S. 



The object of this communication was to bring under discussion the question 

 •whether the difference of Temperature between Polar and Ecxuatorial Seas con- 



