356 
MACKINTOSH’S LECTURES-THE SOLAR SYSTEM. 
for the purpose of illuminating objects in a 
solar microscope. All this accords with the 
light of Uie sun.” We will not discuss the 
point asto how the voltaic lightis evolved, 
since, whatever may be the nature of the pro- 
cess, it appears that the presence of electricity 
is essential to its exhibition. We are, 
therefore, justified in the conclusion, that as 
both lights have some properties in common, 
they are to a certain extent identical. If this 
conclusion be correct, it might be supposed 
that we should be enabled to detect electi icily 
in the sun’s rays. In the Journal des Progres 
des Sciences, this is said to have been effected 
by Professor Salvenio Barlocci, of Rome, 
who states, that when two pieces of copper, 
painted black, one of them connected with 
the upper part of a frog, and the other^ with 
the hind feet, were placed one of them in the 
red and the other in the violet ray of the solar 
spectrum, and then brought in contact, that 
contractions took place in the muscles of the 
frog. This seems to indicate very pointedly 
the existence of a certain specific modifica- 
tion of electricity in the sun’s rays ; and if 
in the rays proceeding from the sun, the con- 
clusion that the sun is highly charged with 
electricity becomes irresistible. Although 
light and heat may be, to a certain extent, 
connected with our subject, we will pass them 
over for the present, as their consideration 
would lead us into too wide a field and create 
confusion. We wish to consider the sun 
simply as the prime, positive, electrical con- 
ductor of the solar system; and with a view 
to fix this idea permanently in the mind of 
the reader, we have denominated him the 
“ centre of positive electricity.” 
2. Region of Negative Electricity. — 
That part of space which surrounds the solar 
system on every side beyond the range of the 
planets, we shall denominate ^he region of 
negative electricity. We shall assign no 
properties whatever to this region, unless va- 
cuity may be considered a property, not a 
perfect vacuum, but nearly so, and especially 
as regards the electric fluid ; it will, therefore, 
have a powerful attraction for electricity, 
which however, it cannot retain, for two rea- 
sons; — 1. 'I his region contains no substance 
upon which the electric fluid can fix; this is 
evident to the senses, for if the immense space 
between the earth and the fixed stars were filled 
with any substance but the most subtle ether, 
it would be utterly impossible that the stars 
could be seen. 2. There are strong reasons 
for the assumption, that all matter issuing 
from the sun becomes decomposed in this 
region, or undergoes some specific change, 
and returns to the sun under its new modifi- 
cation. That this process must be continual- 
ly going on is evident, otherwise even the 
immense bulk of the sun must have been dis- 
sipated long ere this time, from the vast vo- 
lumes of matter continually issuing from his 
surface. We consider, then, that this space 
is in a state of negation as regards the electric 
fluid, and, therefore, has a powerful attraction 
for electricity. An objection may be raised 
to this assumption, upon the ground, that as 
this region is alleged to contain no matter up- 
on which the electric fluid can fix, it cannot, j 
therefore, be supposed to attract electi icily ; 
but since we know from experiment that the 
more the air is rarefied, the less resistance is 
opposed to tlie passage of electricity, and that 
there is a constant tendency in the fluid t© 
escape from the charged body, as is evinced 
by its distribution in the surface— it may be ; 
conceded, that this region offers facilities to j 
the ready dispersion of the electric fluid from j 
the charged body, and this concession is all 
that is required. 
3. If we regard the sun as the prime positive 
conductor of the solarsystem, very’ intensely ■ 
charged with electricity, it will not be difficult !■ 
to conceive him capable of emitting a body of I 
vapour containing a much larger quantity of J 
matter than any comet or planet in the 
system. If we consider that the sun is more 
than a million of times larger than the earth, 
the emission of a comet may be regarded I 
merely as aspark drawn from the prime-con- 'J 
ductor : comets of great brilliancy have been 1 
observed receding from the sun, whose ap- j 
proach to that body had not been detected by j 
diligent observers ; in the absence of direct 
proof, this circumstance alone is almostsuf- 
ficient to justify the inference, that that body 
had just commenced its long and unwearied 
journey around the solar system. We might |i 
refer to volcanic eruption in the earth in sup- 
port of this hypothetical proposition ; but i' 
when we consider the vast concentration of I 
electrical power in the sun, and refer it to the i 
c imparatively feeble efforts of volcanic fire, the 
illustration is too faint to convey an adequate 
idea of the force of electrical action. An evi- |! 
dence of violent internal commotion is furnish- |; 
ed t y the immense moving spots that have been li 
observed on the sun’s disc ; and we know that j| 
in all the natural phenomena that come under 
our immediate observation, if thereis violent I 
internal action, tliereis a constant tendency in |j 
the excited body to relieve or deliver itself ofa !| 
portion, at least, of the exciting cause of the 
commotion. There is nothing extravagant 
then in tlie assumption, tliat comets are dis- 
charged from the sun: the supposition is in j 
perfect accordance with the known phenome- 1^ 
naof nature, and entirely within the range of 
natural probabilities. i 
4. If the sun were in a slate of rest, a comet 
would be projected in a straight line, but as I 
he revolves on his axis with great rapidity, it n 
is projected in a curve, which is the beginning j 
of a ci'cle, thatis to be desciibed Iry the comet I 
in all its future revolutions around the solar \ 
system. If we might be permitted to use a ji 
homelyillustration, thitsbonld bring this i<lea ' 
clearly within the conceptions ot mmds of the 
humblest capacity, wesbould say, thatacomet j 
is projected from the sun somewhat in the 
rnarmertiiat sparks are emitted from the sur- I 
face of a knife-grader’s wheel. As the pro- || 
jectile force is greater than that derived from | 
the sun’s rotary motion, the elliptical form of ( 
the comet’s orbit is determined by the two 
forces conjointly in a ratio corresponding with • 
the force of each respectively. Now as the 
sun and comet are both highly charged with 
positive elec ricity, it follows from the esta- j 
