122 W. H. Hobbs—Mineralogical Notes. 
lead. A complete chemical analysis of the mineral has been 
made on the small amount of material that could be spared for 
the purpose, by Mr. Herman Schlundt in the Chemical Labora- 
tory of the University of Wisconsin. The results obtained in 
the analysis are given below in column I. Under II are given 
the calculated per cents of PbO and CO, in cerussite, and 
under III a recalculation of the analysis after deducting the 
silica, iron, and alumina which are derived from the gangue at 
the point of attachment of the crystals, and which could not be 
mechanically separated without too 1much loss of the valuable 
material. 
i 108 III. 
PHOS Sate eee 80°83 83°52 83:90 
CO! aan 15°51 16:48 16°10 
Fe,O, (and Al,0O,) -- "BS ee oe 
SIO4 4. ea ee 9°15 See iis 
thas ice VU RGA gS trace. ee = ‘Se 
Total cee sete be 99°04 100-00 100°00 
The substance was specially examined for other bases with 
negative results. The quantity of sulphur present was too 
small to be estimated in the quantity of substance available. 
The trace of sulphur and the excess of lead in the analysis 
over that in combination with CO, make it probable that the 
superficial coating on the crystals is galena. , 
Thanks to their metallic coating the crystals reflect well 
wherever it is present, though in other places they afford hardly 
ashimmer of light. By using.a number of crystals complete 
measurement has been possible. The more important angles 
were measured a considerable number of times on different 
crystals. The observed forms are the following: m, »P 
(110); a, 2 P% (100); 7, «0 P8 (180); b, 0 P& (010); ¢, oP 
(001); u, 2P (882); p, P (111); and », » P8 (880); the last 
mentioned form being, I believe, new to the species. These 
forms were determined by the following measurements : 
Measured. Calculated, 
| a 110: Ao Goo 62°46) 
Fee 110A 130 29 10 29 58 
(Pa Sega ie 130A 010 28 438 28 39 
TRO el 110A 010 Sichemsys 5S om 
Vi ae 110A, 100 31 19 3 ae 
IUGR pe eee LIO A832 Zon ro 25 39 
WAG) eine 110 Aaa 34 33 30:) 46 
NICHE ae 110A 001 89 57 90 O 
MAD foe 110K Ss0 ol ery 31 35 
Mminitc wee 110110 54 35 54 28 
MAM ___. (over gap) 62 48 62 47 
mn A Cee 110, 100 as eae 1 27 14 
