BLASTING OF ROCKS—AURORA BOREALIS. 
495 
him, and detailed the methods of analy- 
sis which he adopted, and the results 
at which he a^ri^ ed. This analysis, 
which appeared to have i)een elaborate 
and exact, was conducted in the follow- 
ing manner ; Evaporation to dryness 
gave the total amount of saline matter. 
This was resolved into two parts by rec- 
tified spirit, which dissolved the chloride 
of sodium and magnesium, and left the 
other materials. The residue was treated 
with muriatic acid and alcohol, and the 
various matters taken up estimated in 
the usual way. Finally, what remained 
undissolved by the acidulated spirit was 
found to be a mixture of soda, lime, 
and silex, the relative quantities of which 
were also determined. His final results 
would not appear to differ materially 
from th' se of other chemists. The total 
amount, indeed, of saline matter obtained 
by him was greater, and Dr. Thomson 
suggested that this was probably not 
due to error of experiment, but to the 
circumstance of the waters themselves 
having actually altered in composition, 
a fact which, at least in one instance, he 
had established by experiment. 
Dr. Hare next described his Appara- 
tus for the Analysis, on the plan of 
Volta, of Gaseous Mixtures. It consists 
of two distinct parts, his eudiometer and 
calorimeter ; in the former of which 
he measures and confines, and, by the 
latter of which, he fires the mixture. 7'he 
combustion is not produced, as in the 
case of the common eudiometer, by an 
ordinary electric spark, but by igniting 
with the calorimeter a fine platium wire, 
which traverse'- the gaseous mixture. 
It is unncessary to give a more detailed 
accountof this very ingenious apparatus, 
as it is figured and described in the sys- 
tem of Berzelius, which is, no doubt, in 
the hands of every chemist. 
We should not, however, omit to notice 
a very interesting application which Dr. 
Hare makes of his calorimeter — nam.ely, 
to the blasting of rocks. By this machine 
the powder can be fired at a great dis- 
tance, and several trains also at the 
same instance, — of course, without en- 
dangering the lives of quarrymen ; and, 
should an immediate explosion not take 
place upon setting the calorimeter in 
action, by replacing this instrument in 
the inactive state, which is done in an 
instant, the trajn may be approached, 
without fear that its ignition will ensue, 
— a thing which, according to the ordi- 
nary modes of blasting, can se dom be 
done with impunity. He also alluded 
to an apparatus, in which silicon and 
boron can be readily obtained by igniting 
with his calorimeter potassium envelop- 
ed by the fiuo.silicic or fluoboric gases, 
and complained that an account of this 
instrument, which he forwarded several 
years ago to the Annals of Philosophy, 
had been suppressed. 
Mr. Herapath read a short paper on 
an Aurora Borealis, visible in this city 
on the 18tii of last November, and sug- 
gested as the true theory of this very 
interesting, but rather perplexing, phe- 
nomenon, that it is due to the escape of 
electricity in streams from an excited 
cloud, enveloped by an atmosphere in a 
state of relative dryness. This view was 
supported by Dr. Exley and other gen- 
tlemen, who had observed them in seve- 
ral parts of Great Britain and Ireland, 
but was ably and energetically opposed 
by the President, Dr. Dalton, who con=. 
tended, that Aurorae occur at altitudes 
far above the region of the c‘ouds, and 
also very frequently when clouds are 
al ogether absent. Mr. Herapath, in cor- 
roboration of his views, urged, upon the 
authority of Sir H. Davy, that electri- 
city in motion through a very rarefied at- 
mosphere would be productive of no 
light ; but this statement was contradict- 
ed byDrs. Dalton and Hare, and would 
certainly appear to require confirm- 
ation, for it is inconsistent with ex- 
periments made in an artificial vacuum. 
In connexion with this topic of the Au- 
rora, Dr. Hare entered into some de- 
tails, tending to prove, that within a 
Tornado, such as often occurs within the 
Tropics, there exists a j)artial vacuum, — 
a circumstance which he attributes to 
an electric discharge, which passes be- 
tween the earth and the space beyond 
our atmo.sphere. In both these regions, 
oceans of electric fluid are, to use a 
phrase of the Doctor’s, accumulated; 
and to the discharges which took place 
between them, and between each, and 
charged clouds he see > ed to refer all 
the phenomena of atmospherical electri- 
city. This hypothesis is undoubtedly 
novel ; but, as far as it appe rs to us, 
not in very strict accordance either with 
facts, or the fundamental principles of 
electrical science. It did not excite any 
discussion. 
