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THE POPULAR SCIENCE MONTHLY.

No. 34. On the relation of the Laramie Molluscan Fauna to that of the Succeeding Fresh-Water Eocene and other Groups. By Charles A. White. Pp. 32, with Plates. Price, 10 cents.—A conception of the importance of the subject of this treatise is given by the conclusion which the author expresses, that there is a complete and unbroken stratigraphical series in the region of his exploration, extending from the Middle Cretaceous to the Upper Eocene, and aggregating nearly or quite two miles in thickness. Yet, while sedimentation was not materially interrupted in a large part of the area, the aqueous life was changed, first from that of a purely marine character to that of alternating brackish and fresh waters, and finally to that of a purely fresh-water character, implying great physical changes without materially interrupting sedimentation. The author also observes that in Western North America the fresh-water deposits rival in extent and thickness the great marine formations. Each of the great lacustrine formations described by him has its own distinguishing fauna, the uniform character of which over great areas is quite remarkable.

No. 35. Physical Properties of the Iron Carburets. By Carl Barus and Vincent Strouhal. Pp. 62. Price, 10 cents.—This paper embodies reports of studies of the internal structure of tempered steel, and of the color-effects produced by slow oxidation of iron carburets.

No. 36. Subsidence of Fine Solid Particles in Liquids. By Carl Barus. Pp. 54. Price, 10 cents.—The author considers the dependence of the rate of descent upon the figure and physical constants of a single particle, or upon the constants of a stated group of particles; tries to find some expression for the dependence of subsidence on the molecular conditions of the liquid; and calls to mind the probability of certain permanent chemical effects of the liquid on the subsiding solid. A second chapter is devoted to the results of experiments upon the dependence of the rate of subsidence on the order of surface, concentration, and turbidity.

No. 37. Types of the Laramie Flora. By Lester F. Ward. Pp. 115, with Fifty-seven Plates. Price, 25 cents.—This is an enlargement of the author's "Synopsis of the Flora of the Laramie Group." The plants described and illustrated in it were collected by himself in the seasons of 1881 and 1883. The principal additions to the original work consist of descriptions of species regarded as new, and critical discussions contributing to the proper understanding of the figures and of the nature of the flora under treatment.

No. 38. Peridotite of Elliott County, Kentucky. By J. S. Diller. Pp.,31. Price, 5 cents.—This memoir concerns dikes of eruptive rock, determined as peridotite, which have been observed in Elliott County, and which the author has studied in co-operation with Professor Crandall, of the Kentucky State Geological Survey. It contains a large proportion of olivine, some of it in well-defined crystals, with proportions of pyrope and ilmenite; is associated with nearly horizontal carboniferous sandstones and shales, from which it differs widely in chemical and mineralogical constitution; and is of special interest, because it affords an instance that is rare of peridotite being found under such circumstances that its eruptive character can be fully established.

No. 39. The Upper Beaches and Deltas of the Glacial Lake Agassiz. By Warren Upham. Pp. 84. Price, 10 cents.—The name of Lake Agassiz is given to the extinct body of water which in Glacial times occupied the basin of the Red River of the North. It is assigned to the closing epoch of the Ice age. The exploration of it was begun by the author in 1879 and continued in 1881 and 1885, first under the State Geological Survey, and in the latter year under the United States Survey. The present report covers what was observed in these explorations, which were limited to the prairie regions in Minnesota and Dakota.

Aperçu de quelques Difficultés à vaincre dans la Construction du Canal de Panama. (A View of Some Difficulties to be Overcome in the Construction of the Panama Canal.) By Dr. Wolfred Nelson, of Montreal. Paris. Pp. 71. Price, 1 franc.

The author resided five years on the Isthmus of Panama, engaged in the practice of medicine, and corresponded with several newspapers, besides contributing mem-