of temperature, diurnal and annual, must affect the manifestations of terrestrial magnetism.1
The air that stands upon a single square foot of the earth's surface is, according to Faraday, equivalent in magnetic force to 8160 lbs. of crystallized protosulphate of iron. Such a substance cannot be absolutely neutral as regards the deportment of the magnetic needle. But Faraday's writings on this subject are so voluminous, and the theoretic points are so novel and intricate, that I shall postpone the complete analysis of these researches to a time when I can lay hold of them more completely than my other duties allow me to do now.| Previous chapter/page | Back | Home | Email this | Search | Discuss | Bookmark | Next chapter |