192 Prof. Norton on Molecular Physics. 



minerals to which I have had access are, with one single excep- 

 tion, optically bia.rial. The species that exhibit this character 

 the most clearly arc Cromfordite (muriocarbonate of lead), Scheel- 

 ites of various localities, hyacinth-zircon from the neighbour- 

 hood of Schandau in Saxony, different Wulfenites, and mellite. 

 The biaxial character is exhibited strongest in a meionite from 

 Monte Somma (in others it is comparatively very weak), and in 

 the yellowish zircon from Ceylon. That apophyllites are opti- 

 cally biaxial was established by Sir David Brewster more than 

 twenty years ago. The observations upon mellite were made by 

 M. Reich, Superior Councillor of Mines, and by M. Jenzsch, 

 Councillor of Mines, quite independently of each other. 



The one single exception is Matlockite, which is optically uni- 

 axial. There is also a green uranite, which is so feebly biaxial 

 that many an observer might take it for uniaxial. 



In the rhombohedral system pretty much the same holds 

 good. Tamarite (copper mica), dioptase, the majority of cal- 

 cites, Smithsonite, most apatites, nepheline, most quartzes (pro- 

 bably all), beryl, phenakite, spartalite, Greenockite, and so forth, 

 are optically biaxial. Mimetite from Johanngeorgenstadt is as 

 clearly and strongly so as many a biaxial mica is (Muscovite). 



That biaxial quartzes are met with was already known, and 

 the same is the case with respect to beryl. 



As far as I have proceeded as yet in the determination of the 

 angles of the crystals, not only in the optically uniaxial crystals 

 of the cubic system, but also in the optically biaxial crystals of 

 the pyramidal and rhombohedral systems, those deficiencies of 

 s}'mmetry may be shown to occur to which attention was directed 

 by me some years ago. 



When in the course of last year M. de Kokscharow witnessed 

 in so marked a manner, while with me, the biaxial character of 

 various idocrases, he, of his own accord, observed that he would 

 repeat his measures of that class of crystals. The manganesian 

 idocrase from St. Marcel in Piedmont is optically the most 

 remarkable. 



Freiburg, January 1864. 



XXII. On Molecular Physics. By Prof. W. A. Norton*. 



IT is proposed in the present paper to give a general exposi- 

 tion of a Physical Theory of Molecular phenomena, based 

 upon the highest generalizations, and the most reliable physical 

 conceptions to which the progress of science has hitherto con- 



* From Silliman's American Journal for July 1S64. 



