262 
from some of the paths computed by M. Petit, of the Toulouse Ob- 
servatory, to assume that some meteoric matter arrives from distant 
space, and falls nearly directly to the sun. In such case, the final 
rate of its motion being 390 miles per second, there would be small 
time for much more to be effected, than that that fused crust we so 
often find on terrestrial meteoric stones should be formed, prior to 
the commencement of rapid retardation, and before conversion of 
mechanical energy into heat; followed, doubtless, almost immediately 
by the breaking up of the matter from explosion and deflagration. 
Let us inquire, then, how far the known meteoric mass of 18th 
August 1783 would suffice to produce the effects observed on Sep- 
tember 1st, 1859, had it then fallen to the sun. Professor W. 
Thomson gives the amount of meteoric matter that would be re- 
quired, according to Mr Waterston, to produce, by striking the sun, 
the average solar illumination, as 0*000060 lb. per square foot per 
second. 
For the period of our phenomenon, or 5 minutes, this is *018 lb. 
per square foot, and 501*811 lb. per square mile for the same time. 
Now the meteor in question, said by Mr Cavalho to have had 
a diameter of 1070 yards, can hardly have contained less than 
15,000,000,000 cubic feet; and if we take for its specific gravity 
a mean between what has been determined by many measures of 
earthy meteorites on one hand, and meteoric iron on the other 
(which comes extremely near the mean density of the earth), then 
the total weight must have been 5,250,000,000,000 lb. Whence it 
is evident that there was enough material in that one meteor, pro- 
perly distributed, to keep a space 5,000,000 square miles of the 
sun’s surface in a state of luminous ignition, twice as intense as that 
of the ordinary solar disc during all the time of observation ; and 
therefore, by the transparency of flame, to have tripled the bright- 
ness of the parts passed over — a phenomenon which, from angular 
subtense, as well as intensity of light, would be abundantly visible 
to telescopic observation from our earth. 
* To this we may further add another consideration, which would 
notably increase the quantity of light given out by the same 
meteor ; for in the remarkable investigations which Professor W. 
Thomson has appended to his paper above quoted, relative to the 
* This paragraph added on January 16, 1860. 
