Biographical Memoir of Sir William HerscH'el, 221 
marked with the impress of discovery, than those which pre- 
ceded them. 
In the year 1801, he published his u Observations tending to 
investigate the nature of the Sun , in order to find the causes 
or symptoms of its variable emission of Light and Heat? After 
describing and giving appropriate names to the different phe- 
nomena which appear on the surface of the sun, he considers 
the non-existence of spots, &c., as a sign of a scarcity of lumi- 
nous matter in the sun, and he states it as his opinion that 
the character of the seasons may depend on these phenomena. 
Hence, he is led to support this hypothesis by comparing the 
solar appearances as given by Lalande, with the prices of wheat 
during the same periods, as contained in Dr Smith’s Wealth 
of Nations. In the observations which this paper contains, he 
found that the sun could be seen as white as snow, by obser- 
ving him through a stratum of ink diluted with water, and fil- 
tered through paper. 
The discovery of the two new planets Ceres and Pallas by 
Piazzi and Dr Olbers, afforded Dr Herschel an opportunity of 
observing them with his fine instruments. An account of these ob- 
servations, he published at great length in his paper, u On the two 
lately discovered Celestial Bodies ' ” in the Philosophical Transac- 
tions for 1802. He found the diameter of Ceres to be 163 miles, 
and that of Pallas 110. — he gave them the name of Asteroids, 
from their resemblance both to planets and comets, and he pre- 
dicted that many others would be discovered, — a prediction 
which was soon after verified by the discovery of Juno and 
Vesta, in the very same part of the system. His observations 
on Juno appeared in the Philosophical Transactions for 1805, 
and those on Vesta, in the same work for 1807. 
In the same year, Dr Herschel published his “ Remarks on the 
Construction of the Heavens."” The parts which enter into the 
construction of the Pleavens, he arranges under, 1. Insulated Stars; 
2. Binary Sidereal Systems, or Double Stars; 3. More Complicat- 
ed Sidereal Systems, or Treble, Quadruple, Quintuple and Mul- 
tiple Stars; 4. Clustering Stars, and the Milky Way ; 5. Groups 
of Stars ; 6. Clusters of Stars ; 7. Nebulae ; 8. Stars with Burs, 
or Stellar Nebulae ; 9. Milky Nebulosity ; 10. Nebulous Stars ; 
