378 P. E. Chase on Terrestrial Magnetism. 
that the warm air is charged with moisture which is condensed 
as it ascends, parting thereby with much of its heat and elee- 
tricity, we can hardly deem it necessary to adopt Dr. Dalton’s 
hypothesis that ferruginous matter is the source of atmospheric 
magnetism. Still, the existence of vaporized iron in the air un- 
doubtedly contributes an increased intensity to the magnetic 
currents, and it may probably be an important agent in the pro- 
duction of magnetic storms. 
two vibratory systems above mentioned are conjoined 
during the hours when the sun is above the horizon, and the 
laws of motion applicable to the first system correspond pre- 
cisely, as I propose to show hereafter, with the laws of the solar- 
diurnal magnetic variation deduced from General Sabine’s ad- 
- mirable discussions of the St. Helena observations. It is not so 
Upper regions, where the air is not so much affected by —v" 
ation f the earth, it may oscillate, as suggested by Red 
