MIWERAt-OGY. 305 



4. Magnesia. This earth is light, tasteless, of a perfectly 



white colour, and like the preceding, is infusible except 

 by Voltaic electricity. 



This is not so abundant as the preceding earths, but is 

 found in the composition of several earthy, as well as metal- 

 liferous substances. Native Magnesia which produces this 

 mineral in its purest state, is a substance of rare occur- 

 ence, and has only been met with in New Jersey. 



5. Zircon. Is white, tasteless, rough to the touch, insolu- 



ble in water, and infusible except as the preceding. 



This earth is but sparingly found ; and is at present only 

 known to enter into the composition of three substances, the 

 Hyacinth, the Jargoon, and the Zirconite ; all of which are 

 occasionally used by Jewellers. 



6. Glucine. When pure this is white, soft, unctuous to the 



touch, and of a sweet taste, from which circumstance it 

 derives its name. 



Glucine has only been detected in combination with other 

 substances. The Euclase, Aquamarine, Emerald, and Ga- 

 dolinite; these Minerals though not abundant, are occasi- 

 onally found in mountainous countries. 



7. Yttria. This earth possesses several properties in com- 



mon with the last, like which it has a sweetish taste ; 

 but it is five times, whilst Glucine is only three times 

 heavier than water. 



