SMITHSONIAN EXPLORATIONS, I929 25 



After Dr. Moraes left us early in July, we continued northward to 

 the Bridger Range in Montana. Here some of the earliest work in 

 the West was done and consequently the type localities of several 

 Cambrian formations whose age has recently been brought into ques- 

 tion occur here. As so often happens, restudy showed the strati- 

 graphic history at this place to be much more complicated than previ- 

 ously thought. The Bridger Range has an interesting and peculiar 

 structure for the Rockies in that the northern l)lock is constituted of 

 strata in normal order. Next south we find what may Ijc called the 

 Flathead Pass block which is completely overturned to the east 

 while the southern block on the other hand again has the strata in 

 normal superposition. Strange to relate the sequence of beds in the 

 three adjacent blocks varies, which injects the difficult problems pre- 

 viously mentioned. 



Camping on the west side of the Bridger Range is always pleasant 

 as it aiTords a view across the fertile Gallatin A'alley, probably the 

 most productive portion of the State. Numerous towns and villages 

 dot the floor of the depression through wdiich flow the Gallatin Rivers 

 on their way west to help form the Missouri at the western outlet of 

 the Valley, beyond Logan. Terraces, composed of the exceedingly 

 fertile Bozeman Lake beds whose soil is often over 500 feet deep, 

 yield enormous quantities of dry- farming wheat of such high quality 

 as to be almost world famous. The other topographic feature char- 

 acterizing the A^alley is the irrigated alluvial plains and meadows, all 

 below the benches rimming the inner valleys. Here the towns are 

 located, most of which are flourishing. Bozeman at the eastern and 

 more extensively irrigated section of the Valley is an attractive city, 

 containing a portion of the State University. On the bench southwest 

 of Bozeman, where streams from the Madison Range furnish water 

 for irrigation, a Dutch settlement has grown u]\ to which the inhal)i- 

 tants have given the aspect of a real Holland landscape. Logan, at 

 the western end of the Valley, constituted our base for the summer's 

 work because of its situation at the junction of the Butte and Helena 

 lines of the Northern Pacific Railway, thus allowing mail to go directly 

 to most other sections of the State. Since 1925, when a very heavy 

 earthquake with its focal i)oint near Lombard on the Missouri, caused 

 considerable destruction of brick structures, Logan and the surround- 

 ing vicinity have experienced almost weekly shocks. 



After ten days work in the Bridger Range we moved westward 

 and northward across the Continental Divide into the Blackfoot 

 country where the pre-Cam])rian rocks were examined and an effort 



