428 Royal Institution. 



bian. One of these atoms loses l-t atoms of water, and is converted into 

 alizarine. The second loses 12 atoms of water, and then splits up 

 into verantine and rubiretine. The third takes up the elements of 

 water, and then splits up into rubianine and sugar. Whether it 

 would be possible to confine the decomposition of rubian entirely 

 to one of these processes, or whether all three are essential, he con- 

 siders is a question of the highest importance, not so much in a 

 theoretical as in a practical point of view ; and that should any che- 

 mist succeed in changing rubian entirely into alizarine, he would 

 be the means of giving a great stimulus to many branches of manu- 

 facture and adding largely to the national wealth. 



ROYAL INSTITUTION OF GREAT BRITAIN. 



March 28, 1851. — On the Connexion of Chemical Forces with the 

 Polarization 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 pos- 

 sessing 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 mathematician, indeed, 

 they would, if completely unfolded, supply the data for him to under- 

 take the resolution of the questions of chemical combination and 

 chemical change, by treating them as problems involving the action 

 of mechanical laws. To the chemist, the acquisition of such know- 

 ledge would be the removal of some of the profoundest difficulties 

 of his philosophy ; but such knowledge is only to be sought in the 

 most difficult paths of the whole range of science. 'Tlie question of 

 the connexion of chemical type with crystalline form, the fruitful 

 cause of so much contention 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 imj^licated 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 phaenomena resulting from the property possessed 

 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 expression of the molecular 

 structure of the substance, 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 nevertheless afford a valuable and interesting point 

 of view for studying 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 phse- 



