Abstract: By grinding minerals under water it has been found that they yield relative and reproducible measurements of the hydrogenion concentration resulting from their hydrolysis. Many silicate minerals and two glasses have been studied in this way by a colorimetric method of determining hydrogen-ion concentration, and some of them have been studied more quantitatively by means of the hydrogen electrode. The results of these tests are a rough index of the weathering qualities of different silicate minerals. The effect of silicate minerals on underground waters and upon geochemical changes is discussed.

From introduction: From the time of the publication of the Leadville monograph 2 by the United States Geological Survey, in 1886, the general geology and stratigraphy of the Mosquito Range around the Leadville and Alma districts have been known. In the recent resurvey of the area, however, it has been found necessary to undertake much more detailed studies of most of the formations. In particular, the sediments of Pennsylvanian age and the overlying red beds have received considerable attention and thought. This study was necessary to determine the amount of displacement along some of the notable faults and the depth to older strata that had contained valuable ore deposits in the larger mining districts. In some places the outcrops appear to have been improperly correlated in the older reports. These were given additional study, and considerable revision of stratigraphic sections has been necessary.

Abstract: The identification of new collections of fossil plants from the Green River formation of middle Eocene age made it necessary to reexamine the megascopic types of the Green River flora. This study resulted in the reassignment of some species and the rejection of such species as were based on fragmentary, indefinable specimens. The recent collections yielded 22 new species. Exclusive of the microscopic forms of thallophytes and pollens, the flora now numbers 135 megascopic species that are considered to be recognizable and distinctive. The new elements found in the flora do not alter the previously expressed opinion that the megascopic Green River flora lived in a warm-temperate well-watered environment.

From introduction: This paper describes a small fossil flora from the vicinity of Leadville, central Colorado. The beds from which the flora was collected have long been referred to as the "Weber formation ", though with considerable doubt on the part of many geologists that all the beds so named in Colorado are correlative with the Weber quartzite of northeastern Utah. In current usage these Colorado beds are designated the " Weber (?) formation."

Abstract: The author describes 75 species of plants from the Miocene of about 30 localities in Idaho. These plants represent 40 genera in 28 families and 17 orders, and the most common types are species of Acer, Quercus, Populus, Betula, and Laurus. There are 2 ferns, 3 monocotyledons, and 70 dicotyledons, 18 of which are no longer present in the northwestern United States. There are some xerophytic types, but the majority are mesophytic, possibly indicating a mixture from different altitudes. The beds are correlated with the Latah formation and considered to be of upper Miocene age.

From abstract: This paper is a continuation of the study of the kaolin minerals, in the first part of which, published in 1931, the kaolin minerals kaolinite, dickite, and nacrite were described. In that paper the application of chemical, optical, X-ray, and dehydration methods to the investigation of clay materials were discussed. The present study shows that halloysite is a fourth mineral of the kaolin group, closely related to but distinct from kaolinite. The chemical, optical, X-ray, and dehydration properties of a representative group of halloysites are recorded, all these being new data determined by the authors on separate portions of single samples whose purity has been carefully tested.

From page 127: For the last few years Mr. Henry E. Lee, of Rapid City, S.Dak., has been sending me selected material from the lower part of the Lance formation of Harding County, S.Dak., the exact locality being what is locally known as the Jump Off, an erosion basin of the headwaters of the South Fork of the Grand River, 10 miles north of the East Short Pine Hills. 1 The matrix is a soft gray friable sandstone, and consequently only the coarser, more resistant plants are preserved. In view of the coarseness of the matrix the preservation is excellent, although usually the finer details of venation are obscure. In the sands overlying the plant beds are thin seams of impure lignite.