Elistory of the Discovery of the Planet Neptune. 187 
16. Taking the temperature of solid carbonic acid at — 148° 
F.., and the greatest heat obtained by its reaction with the hydra- 
ted alkalies at from 350° to 400° F., there is an elevation of tem- 
perature produced in this case of more than 500° F. As this 
scale goes far below as well as above the natural temperature, it 
affords an opportunity of exhibiting the effects of intense cold 
and intense heat side by side and proceeding from the same sub- 
stance. ‘These experiments have therefore an illustrative value 
in connection with heat and chemical affinity, as well as with the 
properties of carbonic acid in the solid state. 
Boston, Dec. 20th, 1847. 
Art. XXII.—Hisiorical Notice of the Discovery of the Planet 
Neptune ; by Professor Loomis, of the New York University. 
Tne discovery of the planet Neptune, Sept. 23, 1846, at Ber- 
lin, was announced in this Journal, vol. ii, p. 439; and various 
particulars respecting it have been given in the Numbers for the 
past year. As however the general reader might fail to obtain 
from these detached notices a just idea of the connexion of the 
several links of this most important discovery, it is now proposed 
to place on record a concise history of this planet. 
The discovery of Neptune resulted from the study of the mo- 
tions of the planet Uranus. Uranus was first discovered to be a 
planet in 1781, but it had been repeatedly observed before by dif- 
ferent astronomers, and mistaken for a fixed star. Nineteen ob- 
Servations of this description are on record, one of them dating 
as far back as 1690. In 1821, M. Bouvard of Paris, published a 
set of tables for computing the place of this planet. The mate- 
rials for the construction of these tables, consisted of forty years’ 
regular observations at Greenwich and Paris since 1781, and the 
nineteen accidental observations, reaching back almost a century 
urther. Upon comparing these observations, Bouvard found un- 
expected difficulties. It was impossible to combine all the ob- 
servations in one elliptic orbit. When he attempted to unite the 
ancient with the modern observations, the former might be tole- 
rably well represented, but the latter exhibited discordances too 
gr 
became noticeable ; in ten years the error had amounted to 
Seconp Srrigs, Vol. V, No. 14.—March, 1848. 25 
