Bigelow — Magnetic Theory of the Solar Corona. 261 



Now the distribution of the vapor tension is a function of the 

 temperature of the air, such that it is large at temperatures of 

 100 degrees Fahrenheit and small below freezing ; it, therefore, 

 accumulates over the tropics and gradually diminishes to the 

 poles so that the vapor pressure is very feeble beyond 65 

 degrees in latitude ; at the same time, and for the same reason, 

 it disappears at moderate elevations, highest over the equator, 

 because the temperatures lower rapidly with the altitude. The 

 vapor contents of the air, therefore, practically occur in a 

 zone between 65 degrees of latitude, arching above the equator 

 to the height of 2 or 3 miles. It is just in this region that the 

 electric and magnetic effects in the air are found to take place, 

 and in proportion to the vapor tension, which of course meas- 

 ures the vapor contents; and also it is in this region that 

 principal terms of the diurnal barometric variation have their 

 locus. Furthermore, it will be shown in the Eclipse Report, 

 that the mean variation of the vapor tension in latitude has a 

 representative curve with the same flexure as shown in the 

 above diagram. It seems to me proper to infer that it is the 

 ionization of the vapor contents of the atmosphere which is at 

 once the cause of the phenomenon of the diurnal barometric 

 wave, the atmospheric electric potential and the magnetic 

 diurnal variations, which have, one and all, so long evaded the 

 efforts of research to comprehend. The functional relations 

 between pressure, electric current and voltage, and work 

 energy have been somewhat elaborated by Ebert.* If it can 

 be shown by experiment that a magnetic Held is also produced 

 at the same time as the other effects of ionization, then it will 

 follow, not only that we have reached the correct point of 

 view regarding these subjects, but that Terrestrial Magnetism 

 as a science is distinctly and properly a branch of Meteorology, 

 since its phenomena are produced by the sun's radiation acting 

 on the constituents of the atmosphere in situ. This result 

 will relieve magneticians of the impracticable task of trying 

 to account for these effects by magnetic induction dependent 

 upon electrical currents which are assumed to traverse the 

 earth's atmosphere, as if it were a good conductor. The evi- 

 dence is all against the existence of these electric currents in 

 the lower atmosphere, because the air is a powerful non-con- 

 ductor in these layers ; if it be contended that in the rarefied 

 high strata the air becomes a good conductor, then it is noted 

 that the required magnetic and electrical effects are all located 

 in the lower strata where the aqueous vapor contents are 

 abundant. The fact that electrolytic action takes place readily 



* Unsichtbare Yorgange bei elektrischen G-asentladimgen, Sitzungber. k. bayer. 

 Akad. d. Wiss., 1898. Bd. xxviii, Heft IV. 



