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64 Coyinection of Chemical Forces laith Polarizaiion of L 



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Art. IX. — On the Conyieciion of Chemical Forces with the Po 

 larizaiion of Light ; by Nevil Story Maskelyne, Esq.,M.A.* 



Any facts which can throw light upon the ultimate molecular 

 structure and condition of chemical compounds, cannot fail of 

 possessing interest of a high character, as well for those whose 

 thoughts only casually dwell upon questions of physical science, 

 as for the mathematician and the chemist. To the mathema- 

 tician, indeed, they would, if completely unfolded, supply the 

 data for him to undertake the resolution of the questions of chem- 

 ical combination and chemical change, by treating them as prob- 

 lems involving the action of mechanical laws ; to the chemist, 

 the acquisition of such knowledge would be the removal of some 

 of the profoundest difficulties of his philosophy : but such knowl- 

 edge is only to be sought in the most difficult paths of the whole 

 range of science. The question of the connection of chemical 

 type with crystalline form, the fruitful cause of so much conten- 

 tion among mineralogists as to the questions of mineral species, 

 is one on which we have no complete and sure knowledge ; for 

 the facts of dimorphism show, that implicated with this question 

 are the actions of other forces, such as electric condition, and 

 . above all the mysterious molecular alterations induced by heat. 

 Another direction in which such inquiries have been pursued, has 

 been in tracing the phenomena resulting from the property pos- 

 sessed by many bodies, of modifying a plane-polarized ray of 

 light, by what is termed circular-polarization. This property, 

 from its being proved to be, in a large number of cases, an ex- 

 pression of the molecular structure of the substances, and as such 

 inseparable in many cases from its chemical existence, may be 

 taken, whenever this can be shown to be the case, as an evidence 

 of its individuality, and may be used to determine the question 

 of the permanency or transitory character of the molecular type 

 of the substance. The information thus gained may be but 



vaguely defined, and the truth but darkly seen, yet does it nev- 

 ertheless afford a valuable and interesting point of view for study- 

 ing the molecular nature of bodies. 



M. Biot has been for forty years enriching chemico-physical 



* science by a series of memoirs detailing the results of his study 

 of these phenomena. He has there shown the value of this 

 means of tracing changes in chemico-molccnlar constitution. 



4^ * M. Pasteur has carried forward this inquiry into a new channel 

 ^j tracing a connection between this property in substances, oi 

 circularly polarizing light, and their crystalline character. 



jll t Proceedings of the Eoy. Soc, London, Monday, March 28, p. 45 





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