W. A. Norton—Coggia’s Comet. 163 
e ‘ 
The experiments of Professor Arthur W. Wright, of Yale 
College, on the: gases from stony meteorites,* have furnished 
strong evidence in support of the hypothesis first propounded 
by him, that the cometic substance is gaseous carbon dioxide. 
He found that “in meteorites of the stony kind, the character- 
istic gas is carbon dioxide, and this, with a small proportion of 
carbonic oxide (oxide of carbon), makes up more than nine- 
tenths of the gas given off at the temperature of boiling water, 
and about half that evolved at a low re 4 e spectrum 
of the gases, obtained by passing an electric spark through a 
small tube containing the gases at a low tension, consisted of 
the hydrogen and carbon spectra together. The three bright 
bands of the carbon spectrum were éoincident in position with 
those in the spectra of comets, and had the same relative order 
of intensity. The close relationship now known to subsist 
between comets and meteors renders it highly probable, as sug- 
ested by Professor Wright, that the cometic matter is iden- 
tical with the gaseous matter found associated with stony mete- 
orites, and consists chiefly of carbon dioxide disengaged from 
the nucleus of the comet by the heat of the sun. 
If we adopt this hypothesis with regard to the nature and 
origin of the cometic substance, the question arises in what 
condition does the carbon dioxide exist, in its association with 
the matter of the nucleus? We may at once admit, with Pro- 
of approaching the sun, the increasing amount of heat received 
from the sun should give rise to copious evolutions of the 
* This Journal, III, vol. ix, July, 1875, p. 44. 
