Prof. Challis on the Central Motion of an Elastic Fluid. 31 



No. 12. GneisSj composed of — 



1. Quartz. 



2. Pink orthoclase felspar {\ to \ in.). 



3. Epidote. 



Locality : North of Segaum. 



No. 13. Gneissose granite, composed of — 



1. Quartz. 



2. Red orthoclase felspar (predominant). 



3. Blackish-grcen mica (abundant). 



4. Epidote (traces). 



Locality : Nulla, North of Segaum. 



No, 14. Siliceous breccia, formed of angular pinkish-white opake 

 jasper {\ in.), cemented by silicate of iron, forming a delicate 

 green jasper. Locality : Tertiary beds of Telankhedi. 



No. 15. Crystalline calcareous limestone, containing strings and 

 patches of red hsematite ; possibly of some value as an iron 

 ore. Locality : Korhadi. 



No. 16. Crystalline calcareous limestone, with traces of grossu- 

 larite ; probably metamorphic. Locality : Korhadi. 



No. 17. Brown haematite, in stratified nodular concretions J like 

 the oolitic ore of Leicestershire. Locality : Iron-band of Sil- 

 lewada. 



No. 18. Black tourmaline crystals, in quartz. Locality : Nag- 

 pur City. 



No. 19. Araygdaloidal basalt, decomposing; contains rounded 

 cavities filled with green earth. Locality : Sitawaldi Hill. 



III. Questions in Hydrodynamics : — (I.) On the Central Motion 

 of an Elastic Fluid. (II.) On the Theory o/ Tavtiui^s Beats. 

 By the Rev. J. Challis, M.A., F.R.S., Plumian Professor of 

 Astronomy and Experimental Philosophy in the University of 

 Cambridge *. 



I. TT appears to be established by modern experimental re- 

 -^ searches, that the different physical forces are mutually 

 related by some common condition, or bond of connexion ; but 

 what the precise nature of the connexion is, perhaps experiment 

 alone is incapable of determining. This generalization will be- 

 come matter of exact knowledge only when it is brought within 

 the domain of mathematics. The great desideratum of the ex- 

 isting state of natural philosophy is a mathematical theory of 

 j)hysicul forces. After the explanations that have been given of 



* Commuuicatcd by the Author. 



