130 OC. H. F. Peters—Elements of the Planet Dido. 
We conclude, therefore, soe this mineral contains a small per- 
centage of free silica , and also that a part of the water is basic. 
This latter opinion is Stncrigthiil by the fact that about 12 
per cent of the water escaped at a dull red heat, and that only 
prolonged heating in a platinum crucible for several hours 
would expel the last 1°75 per cent. At least six determinations 
of the water were made in this variety, with the same result. 
The percentages of Numbers I and II are so near that of 
Number III that no material difference can exist in their form- 
ule. While recognizing this fact as respects the chemical con- 
stitution of these minerals, the great rei ar in their phys- 
ical structure leads us to regard Number III as a distinct and 
well marked variety of thomsonite, if not a distinet species. 
We have therefore given it the name Jinionite, in honor o 
Miss Laura A. Linton, a recent student and graduate of this 
University, to whose patient effort and skill we are indebted 
for the analyses given in this paper. 
University of Minnesota, Nov. 20, 1879. 
ART. 2 the Planet Dido ; by Professor C. H. F. 
PE ERs. rom a communication to the Editors, dated 
Litchfield heavens of Hamilton College, Clinton, N. Y., 
January 4, 1880.) 
For the planet Dido (209), I have derived from observations 
of October 25, November 15 and December 7, the following 
elements: 
Epoch: 1880, January 0°0, Berlin m. t. 
M = 201° 56’ 40°°3 
7 190° 41 136 
a= 41°3 
= rr 9°0 
¢= 38°3 
= a 
629" 122 
log a = 0°500848, 
which represent an observation obtained on January 1, when 
it was still very near. The small eccentricity of the orbit is 
remarkable. In consequence of this, there remains consider- 
able uncertainty as to the longitude of perihelion and the mean 
anomaly, but not as to theirsum M+z=L, the mean longitude 
in orbit. 
