186 W. A. Norton on the Variations of the Declination 
Bache, and Lieutenant Gilliss, during the years 1840-1845, have 
also been published. To separate the regular from the irregular 
variations, and ascertain the changes that occur from one season 
to another, &c., the means of the magnetometer readings at each 
observation hour, for periods of a month, three months, half a 
year, or a year, are calculated and published in a tabular form: 
and their variations are also graphically represented by curves, 
the abscissas standing for the observation hours, and the ordin- 
present discussion, In my first investigations on the present sub- 
ject, commenced several years since, I undertook to determine 
how far the diurnal variations of declination, &c., might be rep- 
resented by changes of temperature, directly and indirectly. In 
be traced as subsisting between the disturbances of the mag- 
netic needle, whether regular or irregular, and meteorological 
changes of any kind, occurring at the place; and that accordingly 
if the principle of terrestrial magnetisn exhibits grand features of 
correspondence to that of terrestrial heat, in its normal aspect, 
its more prominent variations, on a nearer view dissimilari- 
ties stand revealed, which indicate that another direction must be 
taken if we wish to gain an insight into the real physical cause 
of maguetic disturbance. Granting that the perturbations of the 
earth’s magnetic force occur without any reference to meteorolog- 
ical changes that happen at the earth’s surface, or in the lower 
atmosphere, we are led to conclude that the seat of magnetic dis- 
turbance is located either in the upper regions of the atmosphere, 
or is coéxtensive with the magnetic matter that pervades the at- 
mosphere and is distributed through the crust of the earth. 
Taking up the former idea, I advanced certain reasons for sup- 
posing that the sun could only act by some emanation, and un- 
dertook to follow out the consequences of a supposed emission of 
some form of magnetic matter from the sun, and the flow in 
every direction over the surface of the atmosphere of the streams 
of this matter that would descend upon the equatorial regions. 
In the present memoir I have adopted the idea that currents of 
electricity are excited in the upper atmosphere, by the sun’s ac- 
tion, and flow in every direction along its surface ; also that cur- 
rents are developed by the sun which flow in a direction parall 
to his equator, or nearly parallel to the ecliptic, and from East to 
West. The conception I have formed of the nature of this ac- 
: is that it consists i 5 in the propagation by ethereal waves of a 
