258 Scientific Intelligence. 
271° 41’. Neptune had this longitude in 1775 ; the comet of 
1812, in 1777; and that of 1846, in 1809. Now, with the 
known period of Neptune and the periods of the comets as de- 
termined by Encke and Peirce, we find (neglecting perturba- 
tions) that— 
Neptune was in longitude 271° Ali in the year re B. & 
the comet of 1812 
1846, av. « 696 a 
It seems, therefore, that “ three bodies were very nearly to- 
gether about 695 years before the Christian era. It is conse- 
quently not improbable that the er, oars form of the two 
comentary orbits dates from this epoc 
Bloomington, Indiana, June 17th, 1869. 
SCIENTIFIC INTELLIGENCE. 
I. PHYSICS. 
1, On the Blue Color of the Sky, the Polarization of Skylight, 
and on the Polarization ‘a Light by Cloudy matter generally ; 
by Jonn Tynpatt, LL.D., F.R.S. —Since the communication of 
aoe by Light,” the experiments upon this subject have been con- 
tinued, and the number of the substances thus acted on considera- 
bly augm mented, New relations have also been established be- 
e R 
questions glanced at incidentally in the abstract referred to,—the 
blue color of the sky, and the polarization of skylight. | Reserv- 
ing the historic treatment of the subject for a more fitting occa 
ing enigmas of meteorology. Indeed it was the praginsl manifest- 
ed in a, i Sir John Herschel, in a letter of sin specula- 
tive pores that sueneed me to enter upon the sendaration of these 
$ 80 Soo 
: inches intern er e vapor to be examined is intro rt 
ced into this tu the manner described in my last abstract, a0 
upon it the condensed of the electric lamp is permit 
beam 
act sue the neutrality or the activity of the substance has been 
ared. 
tt has hitherto been my aim to render the chemical action « of 
light upon vapors visible. For this subst s have 
osen, one at least of whose P ducts of ee, a tie nnd 
dec 
