76 A. Clark on the Sun and Stars photometrically compared. 
gation of a sound in the air is no more difficult to tiie 
than it is to credit the assertion of our aeronauts, a few 
months back heard a musical instrament played on 2s ‘cant 
when their balloon was some three miles above the ite 
That this propagation of the sound of a cannon or a train is 
due to the conduction of the earth, is proved by the fact that r 
is only in certain states of the a independent of wae 
that it occurs. 
ea eed to prevent the r repea ated breaking up of the 
mass 5a and this may be the case in many instances, notwith- 
n associated and per rhaps dissevered masses or even in 
eaere: 
aaa ee 
Wee 
Art. XI.—The Sun gt Bee Stars ear enealy compared ; Mas a 
: Ont a 
we place a lens of known focal distance, one foot for in- : 
dass, between the eye and a star of the first magnitude, or one 
rightness, with sa hg a a 
number of focal distances remaining corresponds to the numbel 
of reductions under which the ge is viewed. 
Castor is iaible, whe rauend, - 103 times. 
Fo! Mux, - - : 11 
> sa = io = - ba 12 
-! - - - 1 20 
The full Moon, - .- - - + 8,000 
The Sun - : - = _-1,200,000 
Epa anally een ran under such a reduction ; 
which pe Ted me to believe that iti 
