Geology and Mineralogy. 231 



After full descriptions of tbe great fields of basalt and the sur- 

 face and intruded outflows, and an account of the rocks — which, 

 although mainly basic, include trachytic, and related kinds and 

 even granite, — Dr. Geikie discusses the origin and history of the 

 disturbances. In the closing summary he observes that, while 

 denudation may have made extensive removals of the lavas, 

 there is still, in the basalt-plateau of Antrim and the region of 

 the Inner Hebrides to the northward, an accumulation of lava 

 streams in some places to a thickness of 3000 feet ; and that the 

 outflows continued until they had filled the hollows of the great 

 valley stretching northward from southern Antrim. The region 

 was then mostly above water-level, as is shown by the leaves, 

 stems, fruits and remains of insects found between the streams. 

 The ejections were mainly of lava, fragmental materials being of 

 small amount. The streams appear to have flowed off almost 

 horizontally, not in Dr. Geikie's opinion from any one center, 

 but rather from many. Reviewing the history he remarks that 

 basic outflows, raising the surface some thousands of feet, were 

 followed by other lavas which solidified as coarsely crystalline 

 doleryte, gabbro, troctolyl e and picryte. Later, probably after vol- 

 canic action had mainly ceased, a renewal of activity brought up 

 trachytic and felsitic rocks, recalling in some respects the 

 trachytic puys of Auvergne, and granophyres and granitic vein- 

 like dikes were made in the felsitic masses or spread out in sheets 

 between the beds below. Still later, basic lavas anew outflowed 

 over the surface. Further, the dikes of pitchstone at Antrim and 

 the region north are probably of yet later origin; for "these 

 vitreous protrusions traverse every other of the volcanic series 

 and do not appear to be cut by any " ; and at one locality the 

 Scuir of Eigg, the streams of pitchstone flowed out over the 

 basaltic plateau, after it had been cut through by valleys, making 

 " an impressive memorial " of the Tertiary topography of the 

 place. 



The greatness of the volcanic results in Tertiary Britain, and 

 not less in many parts of Europe, give emphasis to the fact, 

 alluded to above, that the western border of the Atlantic in the 

 same era from the far north to the West India seas, afford no evi- 

 dence of volcanic fires. j. d. d. 



3. Geological and Natural History Survey of Minnesota. — 

 Volume II of the final Report on the Survey of Minnesota, by 

 N. H. Winchell, assisted by Warren TJpham, has recently ap- 

 peared — a large quarto volume of 695 pages, with forty-two 

 plates. The volume contains reports on the geology of thirty 

 nine counties by one or the other of the authors above men- 

 tioned. Both have made a careful study of the regions. Mr. 

 Upham's attention, as notices of the annual reports in former 

 volumes of this Journal have shown, has been especially directed 

 to the drift — a very prominent feature over the great State, hav- 

 ing special interest from the relations of the State in position and 



Am. Jour. Sci.— Third Series, Vol. XXXVII, No. 219.— March, 1889. 

 15 



