Chemistry and Physies. 433 
of four determinations, 2°398; that of the yellow variety, mean of 
two determinations, 2-402. Before the blowpipe fuses with difti- 
culty to a brown enamel. The following analyses were made by 
ze C. E. Munroe, Assistant in the Laboratory of Harvard Col- 
ege :— 
GREEN VARIETY OF HALLITE. 
Si Al = Fe te Me OU i 
(1) 35°97 7°61 883 1°13 31°34 043 14°32=—99°63 - 
(2) 35°80 7:29 873 1:13 3156 049 14:°33=99°33 
(Mean) 35°89 745 8-78 1:13 3145 0-46 14°33=99-49 
1014... *347 2°65 0°25 12°58 0°08 
e——_ — fi 
19°14 6-10 12°91 12°74 
3 0-96 2°02 2: 
3 ae 2° 2° 
YELLOW VARIETY OF HALLITE. 
Si Al Fe Fe Mg K H 
(1) 35°17 7°74 9°76 0°32 81°61 0°56 14°65—99°81 
(2) 35°34 7:42 961 0°32 31°41 065 14°91—99°66 
(Mean) 35-26 7:58 968 0°32 81°51 061 14°78—99-74* 
18°81 3:53 2°90 O10 1260 0-10 13°14 
ee eee a 
18°81 6°43 12°80 13°14 
3° 1:03 2 2°09 
3° 9° Vy 
1° 
tte; a. . Oa . St, . 12H, 0. 
Biotite from Greenwood Furnace. Mr. Hall informs me that -_ 
tag perfect crystals have only been found in one pocket of the 
rpentine, : 
_ The distinction, however, between the phlogopites and = 
biotites is not fundamental, either chemically or physically. 
* Trace of manganese. 
