Il6 HISTORY OF THE MUSEUM. 



presenting the minerals in their pure state, he 

 taught the pupil to distinguish the variations pro- 

 duced by a mixture of different substances. He 

 repeated the most curious experiments on the 

 action of electricity, magnetism, and light ; phe- 

 nomena then recently observed, which offer pre- 

 cise characters depending on the chemical com- 

 position of the body. The collection of the cabinet 

 affords the means of tracing the transitions and 

 differences of form, and above and below the 

 specimens for study, are exhibited larger masses 

 of the same species, by which the general aspect 

 may be better ascertained. M. Haiiy himself pos- 

 sesses a suite of crystals almost complete, which 

 serve as examples in the lectures, and save the 

 trouble of displacing those in the gallery. He 

 does not confine his instructions to the lecture- 

 room, but willingly affords his pupils more par- 

 ticular explanations at his own house. 



The influence of this method has been felt in 

 foreign countries: the Germans associate the new 

 characters with their own classification, and 

 several works have been published uniting the 

 principles of Werner and Haiiy, or those of the 

 German and French schools. 



Since the new organisation M. Desfontaines 

 has had no occasion to change the method intro- 

 duced by him in 1786. His lectures are given 



