198 A, Gautier on recent Researches on Nebule. 
This quantity, however, may be brought nearer to our compre 
hension by comparison with other cosmical magnitudes. The 
nearest celestial body to us (the moon) has a mass of about 
90,000 trillions of kilograms, and it would therefore cover the: 
expenditure of the sun for from one to two years. e mass of 
the earth would afford nourishment to the sun for a period of 
from 60 to 120 years. i 
To facilitate the appreciation of the masses and the distances 
occurring in the planetary system, Herschel draws the following 
picture. Let the sun be represented by a globe 1 metre in diam- 
eter. The nearest planet (Mercury) will be about as large as 
a pepper-corn, 3$ millimetres in thickness, at a distance of 40 
metres. 78 and 107 metres distant from the sun will move 
Venus and the Earth, each 9 millimetres in diameter, or a little 
. larger than a pea. Not much more than a quarter of a metre 
from the Earth will be the Moon, the size of a mustard seed, 
24 millimetres in diameter. Mars, at a distance of 160 metres, 
will have about half the diameter of the Earth; and the smaller 
planets (Vesta, Hebe, Astrea, Juno, Pallas, Ceres, &c.), at a dis: 
nee of from 250 to 800 metres from the sun, will resemble 
particles of sand. Jupiter and Saturn, 560 and 1000 metres 
distant from the centre, will be represented by oranges, 10 and 
9 centimetres in diameter. Uranus, of the size of a nut 4 centr 
metres across, will be 2000 metres; and Neptune, as large as an 
apple 6 centimetres in diameter, will be nearly twice as distant, 
or about half a geographical mile away from the sun. rom 
Neptune to the nearest fixed star will be more than 2000 ge — 
graphical miles. 
ieee a 
. GAUTIER.’ 
Labors of Lord Rosse; First Memoirs.—Since 1827 Lord Ross 
has been engaged in the construction of large specula for Oo 
nomical telescopes. In 1839 he finished his first telescope ¥ af 
had a speculum three feet in diameter with a foca distance | 
rf feet, and he described the method of constructing it me wi 
" Translated for this Journal from the Bibliothéque Universelle, for June, ot 
Art. XVI—<Second Notice of Recent Researches relating to Nebula; 
by A i 
* 
. 
