C. H. F. Peters—A New Planet. 129 
trough of some deep wave of the sun’s edge. The last contact 
occurred at 65 0™ 36*7, Harvard Coll. Observatory mean time. 
No trace of the planet was seen after it left the limb of the sun, 
but the sky was not very clear and the image was too unsteady 
to make delicate observations. 
The luminous ring observed around Mercury in transit has 
generally been attributed to the horizontal refraction undergone 
by the rays of the sun in passing through the dense atmosphere 
which is supposed to envelop this planet. This explanation 
seems quite plausible, although it is difficult perhaps to con- 
ceive how atmospheric refraction alone can produce such a 
phenomenon, and it would seem that something else is wanting 
to fully explain it. Perhaps the refraction theory might some- 
what be helped by the fact that the sun, having a vastly greater 
diameter than Mercury, must necessarily illuminate at all times 
more than one-half of the globe of this planet, and this surplus 
of illumination must be visible from the earth during transits, 
and appear as a thin luminous ring surrounding Mercury. Of 
Cambridge, May 8th, 1878. 
Art. XITI.—Discovery of a new Planet ; by Professor C. H. F. 
Prrers.—From a letter to the Editors, dated Litchfield Ob- 
servatory of Hamilton College, Clinton, N. Y., July 3, 1878. 
On June 18th 1 marked upon my chart, quite near to a star 
of the 11th magnitude, another of the 12th or 18th magnitude; 
and on June 19th this star was no more in its place. I there- 
fore drew upon the chart all the small stars in the neighbor- 
hood; but before the one among these that had revealed itself 
