196 Notes Illustrative of the 



comes clown with great violence, and often devastates the 

 adjoining country. 



The aspect of the valley between Wanianabaddy and 

 Amboor is monotonous and uninteresting. At the latter 

 place I was much interested by the marked development of 

 the phenomena of crystallisation in the structure of the 

 trap dykes, which traverse the neighbouring hills in great 

 abundance. It is unnecessary however to describe these in 

 detail here, as I have elsewhere done so at considerable 

 length.* It may therefore suffice to remark, that the trap 

 invariably on being fractured exhibited cleavage planes, and 

 separated into obtuse angled rhomboids; that fissures tra- 

 versed the dykes always at right angles to the cooling planes 

 or sides of the including sienite ; that the direction of cleav- 

 age was perpendicular to that of fissures ; and that the trap 

 was evidently altered at its planes of junction with the 

 sienite. In attempting to trace the cause of these pheno- 

 mena we are carried to the unexplored domain of modern 

 science, for their development is dependant on the action of 

 molecular forces, whose origin and mode of operation are 

 alike enveloped in much mystery. Mathematical analysisf 

 has been successfully employed in demonstrating that, grant- 

 ing certain postulates, the phenomena of crystallisation may 

 result from the adjustment of electrical forces ; and observa- 

 tion tends apparently to confirm such a theory, by shewing 

 that crystals do actually result from the action of forces 

 derived from this source. But, we are still required to ap- 

 ply these conclusions with diffidence, as their verification 

 cannot yet be considered as effected. The existence of 

 electricity during the passage of trap dykes from their ori- 



* " On the crystalline structure of the trap dykes in the sienite of Amboor, 

 &c. &c." Madras Journal of Science, July, 1839. 



f M. Mosotti sur les Forces qui regissent la constitution interieures des corps 

 Whewell's Hist, of Indue. Science. Sommeville Conn, of Phys. Science. 



