1 882.] On the Application of Solar Physics. 399 
occur at the period of most sun-spots ; but here, again, I am 
not aware that there is any proof to show that these dis- 
turbances are the result of a thermal storage of electricity 
at this time. From Dr. R. Capron’s work on the “ Aurorae 
and their SpeCtra ” we learn that these disturbances, which 
are of the same nature as thunderstorms, occur mostly in 
March and October ; that their curves of greater frequency 
tend towards the region of atmospheric pressure, and that 
they bear the same relation to the limit of perpetual ice. 
This, as I take it, refers their causation, like the wind and 
rain, to a differentiation in the temperature. As regards the 
seismic disturbances, earthquakes quiver and volcanoes are 
aCtive at two points in the sun cycles. They break out when 
the sun-star has fewest, and again when it has most, spots 
on its photosphere. This remarkable truth, as far as I can 
learn, was first enunciated in its entirety by Dr. Fuchs, in 
his pamphlet “ Die Vulkanischen Erscheinungen der Erde,” 
published in 1865 ; but some thirteen years earlier we find 
it related, in the publication of the “ Naturforscher Gesell- 
schaft ” of Bern, that a discussion had arisen between Prof. 
Wolf and M. E. Kluge as to whether it was a faCt that the 
Aurorae Boreales and earth tremors accumulated during the 
years when the sun-spots were most prevalent and the mag- 
netic variations were most remarkable. Still if anyone will 
take the trouble to tabulate the eruptions of Etna and Vesu- 
vius, — say between 1755 and the present time,-— I think the 
only wonderment that will arise in his mind will be, How is 
it that this matter was not found out long before ? It is 
ages since old mother Etna was discovered to be the poor 
man’s weather-glass. Sir John Maunderville, that most 
susceptible and credulous historian of the East, relates — 
“ Also in that isle, Sicily, is Mount Etna, which men call 
Mount Gybell, and volcanoes that are ever burning. And 
there are seven places which burn and cast out flames of 
diverse colours ; and by the changingof those flames, men of 
that country know when it will be dearth or good time, or 
cold or hot, or moist or dry, or in all other manners how the 
time will vary.” But do the earthquakes and eruptions 
inform us whether the sun is colder or warmer when it is 
most spotted ? Allowing these may be due to the thermal 
expansion and contraction of the earth’s crust producing 
lateral thrust, it would not appear that any positive data 
are possible, unless it can be certainly stated when the 
earth’s surface is most expanded and when it is most con- 
tracted. The eruption of volcanoes and the earthquakes 
might result from excessive expansion or extreme contraction, 
