246 GLOSSARY 



sphere, the biosphere, the lithosphere, the tekto- 

 sphere, and the centrospher« ; these are known as 

 geospheres. 



Hydrosphere. — ^The aqueous envelope of the globe, 

 including the ocean, lakes, rivers, and the moisture 

 which the atmosphere always contains, and the water 

 which has penetrated deep into the lithosphere. 



Ion. — ^A form of molecular aggregation of matter in 

 aqueous solution. An inorganic salt, base, or acid 

 is partly split, when in solution, into ions. The metals 

 mostly give cations, which carry a negative electrical 

 charge and go to the positive pole in electrolysis. 

 Acid radicals and certain non-metals form positively 

 charged anions. In any solution the total negative 

 charges on the cations exactly balance the total 

 positive charges on the anions. It is impossible to 

 isolate ions as such ; when compelled to assume the 

 solid state, they combine with one another to give 

 electrically neutral molecules. 



Katabolism. — See MetaboUsm. 



Lithosphere. — The rocky crust of the earth, a designation 

 corresponding with atmosphere, hydrosphere, etc. 

 See Geospheres. 



Mean Sphere Level. — ^The level of the lithosphere if 

 smoothed off and covered by the ocean, which would 

 then be of a uniform depth of about two miles (1700 

 fathoms). 



Metabolism. — The property characteristic of living matter 

 of assimilating substances different from itself, of 

 building them up into its own substance (anabolism), 

 and of again decomposing these complex molecules 

 into simpler ones (katabolism), with production of 

 energy in the form of heat, movement and electrical 

 phenomena. Metabolism results not only in the 

 generation of energy, but also, if anabolism be in 

 excess of katabolism, in increase of bulk and con- 

 sequent growth and reproduction. 



