Scientific Serials

Abstract

American Journal of Science, July.—A new Erian (Devonian) plant allied to Cordaites, by Sir William Dawson. This únique specimen from the lower Catskill (Upper Devonian), Wyoming County, Pennsylvania, presents the peculiarity of combining the fructification of the Cordaiteæ with foliage akin to that of Næggerathia, thus connecting two Palæozoic groups which are now considered as allied to Cyadeæ and Taxineæ.—The law of thermal relation, by William Ferrel. The object of these researches is to compare Dulong and Petit's older formulæ and the more recent determination of Stefan with the principal available data derived from experiment and observation, with a view to ascertaining what modifications these formulæ may require in order accurately to represent the true law of relation between the intensity of the radiation and the temperature of a body. It appears generally that neither of the formulæ in question represents the true law of Nature through the whole range of experiments, but that different values are required for different ranges of temperature. To determine the true mean value with greater accuracy experiments upon radiation will have to be made at much lower temperatures than any yet made.— Stratigraphic position of the Olenellus fauna in North America and Europe (continued), by Charles D. Walcott. Since writing the first part of this article the author has completed the survey of all the species known to him from the Olenellus (Lower Cambrian) zone in North America. From a general comparison of this zone with the Ordovician the superiority of the latter in number of species, genera, and families becomes at once apparent. But when the comparison is extended to class characters, the disparity is much reduced, and it is made evident that the evolution of life between the two epochs has been in the direction of differentiating the class types that existed in the earlier fauna. It cannot be asserted that the Olenellus fauna of Europe and North America was contemporaneous, although its relations to the succeeding Middle and Upper Cambrian and Ordovician is everywhere essentially the same, the Olenellus being the basal fauna wherever it has been found.—On allotropic forms of silver (continued), by M. Carey Lea. The properties are given of the two already described insoluble forms of allotropic silver, which differ from normal silver especially in their sensitiveness to light, their brittleness and specific gravities (9˙58 and 8˙51, the normal being 10˙5).—The peridotite of Pike County, Arkansas: Part I., description and general relations, by John C. Branner; Part II., microscopic study, by Richard N. Brackett. Though small in extent, the exposure of peridotite occurring near Murfreesboro, Pike County, is geologically important, as offering a clue to the time and character of the disturbing influences which about the close of the Cretaceous sank the greater part of Arkansas and other contiguous regions beneath the ocean. It is also interesting as being the third reported occurrence of picrite-porphyry in the United States. Its position and topographic features are shown in the accompanying map.—Papers are contributed by T. M. Chatard, on urao, shown to be the true natural form of sodium carbonate; by Edward F. Ayres, on the crystallization of trona (urao), from Borax Lake, California; by G. F. Kunz, on fluorite, amber, opal, and diamond; and by O. C. Marsh, on the discovery of Cretaceous Mammalia by J. B. Hatcher in the Laramie formation of Dakota and Wyoming. There is also a reprint of Mr. James Croll's paper in the Quarterly Journal of the London Geological Society for May 1889, on prevailing misconceptions regarding the evidence of former glacial periods.