312 G. J. Brush—American Sulpho-Selenides of Mercury. 
have been inadvertently omitted in the cut. One of these 
(Carrollton) lies on the 8° 80’ line, a few miles north of the 
i nother (Glasgow) lies on the ‘river, a little south of 
east from Carrollton. The third (Columbia) lies just east of 
the 8° line, and southeast from Carrollton. A fourth station 
omitted is nearly due east of the southern terminus of the 
line, and just outside the 7° 30’ loop. The other stations, rep- 
resented by the small circles are shown on the cut, and an in- 
spection of the map will show the weight to be given to differ- 
ent parts of the lines. At stations situated at points of abrupt 
curvature of the lines, the observations have been repeated at 
various localities in the region, until it was clear that no min- 
ute local effects existed. 
he value in the Iron Mountain region is the mean of 
many hundred determinations made with a solar compass by 
Pumpelly and Moore, in 1872. This region is in the east part 
of the 7° 30’ loop. In the western iron field, which is nearly 
coincident with the 7° oval, our observations were repeated at 
various points (our aim being to avoid iron deposits), without 
finding any local action. In conducting this survey, a mag- 
netometer belonging to Washington University was used, but 
the dip circle and declinometer were kindly furnished by Pro- 
fessor J. E. Hilgard, of the U.S. Coast and Geodetic Survey. 
Thus far the survey has been conducted wholly on private 
means, in which we have been aided by the railroad compa- 
nies, and by citizens of St. Louis. A bill providing for the 
i ea of the survey is now before the legislature of the 
te. 
ArT. XXXVUL—On American Sulpho-Selenides of Mercury ; 
by Gxo. J. BrusH— With analyses of Onofrite from Utah ; 
y W. J. Comstock. Contributions from the Sheffield 
Laboratory, No. LXI. 
AT a meeting of the National Academy of Sciences, held in 
New York in November last, Professor J. S. Newberry com- 
municated to the Academy two papers, on the occurrence of 
various ores in Southern Utah, mentioning, among others, 
the discovery of a mercuric selenide at Marysvale, a mining 
camp two hundred miles south of Salt Lake City. 
A specimen of this mineral was given me by Dr. Newberry, 
and desiring to ascertain more definitely its specific relations; I 
made a pyrognostic examination of it, and found it to be essen- 
tially a sulpho-selenide of mercury with traces of zinc an 
manganese, and that the mineral was probably identical with 
Rose’s Onofrite. On communicating my results to Dr. New" 
