MINERAI/OGY. 317 



been used with other substances in the formation of red 

 •olours known by the name of Lakes. 



22. Chrome. This substance has neyer been found in a 

 Metallic state, only entering into the composition of 

 some few substances ; the Emerald is supposed to owe 

 its brilliant green colour to its combination with this 

 rare Metal. i 



23. Rhodium. This Metal is not malleable, it possesses a 

 bright Metallic lustre, and is about eleven times heavier 

 than water. 



24. Osmium. Is of a dark grey colour. 



95. Iridium. When pure is white and infusible. The 

 three last named Metals are very rare, having only been 

 found alloying the native Platina of Peru, and have 

 not been applied to any useful purpose. 



26. Uranium. Has never been found in a Metallic state ; 

 its colour is dark grey, its substance is brittle, and may 

 be cut with a knife ; it is the lightest of all Metals ex- 

 cepting Tellurium, being only six times heavier than 

 water. It has not been applied to any use. 



27. Cerium. This like the last has never been found in 



a Metallic state, and has only been obtained with con- 

 siderable difficulty by the Chemist it enters into the 

 composition of a few rare Minerals, 



