, ..yst 



68 Scientific Intelligence. 



basaltic rock, a formation appearing low down on the Yukon also). 

 They are also the top-rock at the Shumagin Islands, where we 

 have a very pretty section down to theTriassic or Jurassic syenites, 

 which are the base rock of the country nearly every where. 



(1) The marine brown sandstone with Crepidula, whale verte- 

 ers, and fossil teredo-bored wood. 



nglomerates brown and iron-stained with thin sandy 

 layers bearing Sequoia and other vegetable remains. 



'{■■]) Bluish sandy slates and shales with Platanus leaves inter- 

 stratitied with conglomerates and layers of silicitied wood and 

 lignite beds. (This is the Miocene of Newberry and Heer.) 



(4) Quar'zites much metamorphosed but conformable. 



(5) Syenites (or granites without mica). 



Through all the later strata (1-4) irregular ejections of basaltic 

 lavas. 



The sketch of the Shumngiu section, herewith sent, was made 

 ten years ago. It is typical of the general sequence in many parts 

 of the territory. At Bering Strait there are no fos^ilifcrous rocks. 

 The Diomedes are granitic domes, rounded and weathered into 

 irregular shapes, but domes of " massive eruption'' on Kichtho- 

 fen's hypothesis. The rocks of the Asiatic side are nearly all 

 syenitic (at least so wherever I have landed). The American side 

 is mostly the nietamorphic quartzitcs and hard blue slates not 

 fossil-bearing, with oecasional patches (as in Kotzebue Sound) of 

 lava and basalt of late origin. Northward we have the great 

 ground-ice formation broken here and there by hills of Paleozoic 

 age with characteristic fossils and coal of good quality. 



On Aliaska Peninsula we have fossiliferous strata from the Jura 

 up. with the same syenitic basis and superimposed Tertiary rocks. 

 The Miocene plant and marine strata, as here considered, have not 

 been noted northwest of the east coast of Norton Sound on the sea- 

 coast, nor much north of Nulato on the Yukon. Leaving them 

 and going east on the river, we come upon quartzites and con- 

 glomerates, and strike the syenite at the junction of the Yukon 

 and Tananah Rivers; farther eastward the region is probably 

 Devonian, but covered by alluvial deposits near the river; the 

 Devonian rocks actually come out near Fort Yukon, on the Por- 

 cupine River. 



The general depression of the Alaska region indicated by the 

 Tmti.nv beds probably could not have exceeded l.Vxi feet* and 

 perhaps less. But how to reconcile the general absence of 

 T the region <(<ljace,<tto tin strait with 

 not quite clearly see. There was a de- 



u. xjukjou yjj vxjiimi* KiuuvllUt ■ , uv J. a.. Jri 



letter to J. D. Dana, dated, Geological Surve , „. 



15, 1882.)— Mr. G. K. Gilbert and Professor J. LeCoute's articles 



on the "Origin of Jointed Nru.-tiuv in undisturbed Clay : 



