78 GEOLOGY. 



three parts of common salt with one part of black oxide 

 of manganese, and having introduced the mixture into a 

 glass retort, pour upon it two parts of sulphuric acid, and 

 apply the heat of a lamp, the gas will come off abun- 

 dantly, and must be collected by means of the pneumatic 

 trough. Great care should be taken that it does not es- 

 cape in a room, as a comparatively small quantity will 

 produce a violent irritation of the lungs. It combines 

 with certain salts and metals, and its combinations are 

 termed chlorates and chlorides. 



Nitrous oxide gas is the last intended to be noticed, 

 and is a compound of oxygen and nitrogen. It supports 

 combustion better than common air, and maybe respir- 

 ed. But the effects produced by inhaling it, constitutes 

 its chief peculiarity. The most pleasurable sensations 

 are the general results, producing immoderate fits of 

 laughter, whence it has obtained the name of laughing 

 gas. The excitement in some persons is so great as to 

 produce violent muscular motion, and an inclination to 

 leap and run. Unlike excitements in general, it does 

 not appear to leave any unpleasant feeling after the ex- 

 citement has subsided. This gas is obtained from 

 crystals of nitrate of ammonia, by submitting them to 

 the heat of a lamp in a glass retort. 



GEOLOGY. 



Introduction Primary Series of Rocks Divided into Crystalline and Sediraen- 

 ,. tary Crystalline Considered Volcanic Action Sedimentary Rocks Tran- 

 sitive Series Divided into Cambrian and Silurian Organic Remains in 

 Transitive Series Secondary Series Names and Subdivisions of Secondary 

 S er i es _ Each Group in Secondary Series considered Organic Remains in 

 Secondary Series Tertiary Series Names and Subdivisions Kocene 

 Meiocene Pleiocene Organic Remains in Tertiary Series Diluvial and 

 Alluvial Deposits The London and Hampshire Basins Conclusion. 



GEOLOGY is that science which treats of the structure 

 of the earth, and of the substances of which it is com- 

 posed. 



The earth is a spherical body whose diameter is 

 nearly 8000 miles, and consequently its radius, or the 



