

r891.] Geology and Paleontology. 1121 
II. As to origin, he is at variance with others who have worked in the 
same field, in that he holds the porphyries as well as the granites to be 
ancient eruptives rather than metamorphosed sediments. 
The Archean age of these rocks had been fully established, but Mr. 
Haworth’s observations gave him newevidence, confirming the accepted 
view, which he groups under two heads: 
1. Absence of contact metamorphism in the surrounding Paleozoic 
rocks, ; 
2. Inclusion of numerous fragments of crystalline rocks almost every- 
where, in both sandstone and limestone. 
In proof of his eruptive theory of the origin of the rocks, Mr. 
Haworth presents the following evidence in detail : 
A. Field evidence of the eruptive origin. 1. Absence of true bed- 
ding. 2. Flow structure, banded structure, and lithophyse. 3. Brec- 
cia. 4, Scoria and amygdaloids. 5. Tuff. 6. Absence of gradations 
of crystalline into non-crystalline rocks. 
B. Petrographic evidence of the eruptive origin. 2. Texture of the 
ground-mass in the porphyries and breccias. 2. Flow structure in the 
porphyries and breccias. 3. Broken crystals due to the flowage of lava 
after the crystals were formed. 4. Magmatic corrosion of porphyritic 
crystals, and of fragments in the breccia. 5. Amygdaloids. 6, Ab- 
sence of metamorphic mineral 
The paper is well illustrated with plates and sketch maps, which 
add materially to its value. 
The Sulak Gorge.—In a paper on the Transverse valleys in the 
Eastern Caucasus, Professor Sjögren gives the following description of 
the Sulak Gorge, below Gimri, in Daghestan : ‘‘ Among the many val- 
leys of Daghestan that are interesting to the geologist, there are none 
more remarkable than the channel by which the river Sulak passes 
through the chain of Cretaceous and Jurassic mountains which borders 
Inner Daghestan. Just above the entrance to this defile the four 
rivers Koissu unite in one stream, which, in series of cataracts, tears 
through a tremendous chasm some fifteen miles in length, cutting the 
huge ridge almost at right angles to its axis. 
“ The gorge traverses the main ridge in the direction north, forty 
degrees east, then changes its line to northwest, which it still follows 
at the widening of the valley below Tjirkei, and finally comes back to 
due north, as it passes through the Tertiary hills below Subut. . . . 
The huge cutting has a vertical depth of from 5,000 to Saas feet, 
while its breadth is so small that the river leaves no room, sig a proper 
Am, Nat.—Dec.—6. 



