D, Kirkwood on the origin of the Comets of 1812, ete. 255 
Ephesite. Lesleyite. 
Silica oe Le eee 30°70 31°18 
Alumina 2 203 55°67 55°00 
HIG a Se et ee ee 2°55 0°45 
Soda 6°52 1°20 
Potash Geer 390 7°28 
Water 2c 2 a1 4°80 
100°45 99°91 
The alkalies in the two varieties are reversed, the Ephesite 
containing principally soda, and the Lesleyite potash. : 
This close relation of the two minerals is an interesting 
fact as regards the associate minerals of corundum found in 
different parts of the world. : 
In regard to the reddish variety of Lesleyite examined by 
Roepper, the analysis cannot be considered as giving very satis- 
factory results, for the mineral may have been impure, and the 
culty in decomposing by the soda fusion may give very 
erroneous results in a silica determination. 
Louisville, Ky., August, 1869, 
Ant. XX VIII.—On the Origin of the Comets of 1812 and 1846 
IV; by Prof. Danie, Kirxwoop. 
THE comet of 1812 was discovered by Pons on the 20th of 
July, and continued to be observed till about the last of Sep- 
tember. It became visible to the naked eye shortly after its 
discovery, its tail attaining a length of more than 2°. 
