204 S. W. Burnham—Seventh Catalogue of New Double Stars, 
in the hornblende and mica schists of bed XIX, at the contact 
with the overlying granite bed. 
Granite dykes are very numerous in the Laurentian. 
2. Hornblende and Pyroxene Series. 
Some geologists would include here a considerable portion 
of the bedded greenstones embraced under metamorphic rocks, 
“Trap”-dikes in a bed of magnetite occur at the Washing- 
ton mine. At a few other points very small ones have been 
seen. Black, fine-grained, massive, hard, tough. Has been 
called doleritic, dioritic, and, by Dr. Wichmann, diabase, (Has 
but little resemblance to the bedded rocks so-named)—7o, 94. 
The greenstone dikes, sometimes of great thickness, so numer- 
ous in the Laurentian, are not so fine-grained and are more 
dioritic in character. 
8. Hydrous Magnesian Schistose Rocks. 
These are found in dyke-like masses crossing quartaytes, 
iron-ores, and greenstones, sometimes apparently formed from 
the abraded material of the walls of a fault,*—73. Sometimes 
the rock is erratic, as in the case of the soft chloritic? schist 
dyke in massive quartzyte at the northeast corner of Teal Lake 
ot observed in the Laurentian. 
Dresden, Saxony, Dec. 21, 1875. 
Art. XXVI—Seventh Catalogue of New Double Stars; by 8. W. 
BURNHAM. 7 
THE double stars in the following list have been discovered 
during the past year with the Clark & Sons 6-inch refractor 
previously used in these observations. The six catalogues Pre 
ceding this will be found respectively in Monthly Notices of the 
Royal Astronomical Society for March, May and Doccmam 
1874, June and N ovember, 1875, and Astronomische Nachrich- 
ten, No. 2062. The reference number in the first column 18 
continued through the series. been 
Four pairs from the old double star catalogues have 
found to be again more closely double. These are: 
‘ go 39 
H 4935 
w IIL 113 (== 2630 rej) 
H 1489 a 
Through the kindness of the distinguished observer, ie 
Dembowski, I am enabled to attach his careful microme 
measurements of a few of these objects. 
* Faults of any great magnitude are rare in the Huronian. 
