PRESIDENT S ADDRESS. 



aucl no crystals showing inteimediate characters, while again 

 the passage to anorthite as the quantity of albite was 

 diminished was also quite abrupt. 



In addition to those imitations of the natural minerals, 

 MM. Fouque and Levy produced the equivalents of oligoclase, 

 labradorite, and anorthite, when stroutia, baryta, and oxide of 

 lead were substituted for lime. These present some very 

 interesting peculiarities ; some are apparently orthorhombic, 

 while others are certainly triclinic, but do not present the 

 usual twinning on the albite plan. 



I fear, ladies and gentlemen, that you will think that what 

 I have laid before j'ou this evening bears perhaps too great 

 marks of its essentially eJastic origin, and I should have been 

 glad to have been able to submit the materials to a more 

 thorough metamorphism, but I trust you will not have found 

 the subjects introduced to your notice quite devoid of interest, 

 and I think they somewhat indicate the path along which 

 geological inquu-y is just now travelling towards a solution of 

 some of the great chemical as well as stratigraphical problems 

 which are propounded to us in the present condition of the 

 earth's crust. 



