﻿320 Scientific Intelligence. 



tion, freezing and fire. As an allowance of ninety per cent is 

 now made by architects for error in the values of crushing 

 strength ordinarily quoted, the author desired to devise tests that 

 more closely measure the characteristics of stone under natural 

 conditions; he said that strength should be determined by mod- 

 erate, long-continued pressure that causes a slow yielding, rather 

 than by heavy, violent pressure that produces immediate crushing; 

 that the stone should be continued underpressure at least a month. 

 Frost was found to be more active in removing particles that had 

 been loosened by chemical weathering than in direct mechanical 

 breaking of unweathered rock. 



Geology of Southwestern Colorado. — The geological features of 

 a district in southwestern Colorado were described by Dr. T. B. 

 Comstock in several papers. The mines of Red Mountain are 

 found to be situated in a region of extinct geysers, many mounds 

 around the old vents being larger than any now known in the 

 Yellowstone Park ; the galleries opened in them give excellent 

 opportunity for the study of geyser structure and of mineral depo- 

 sition along the old conduits. The distribution of lavas in the 

 same region suggested a mechanical explanation for von Richt- 

 hofen's classification of volcanic rocks, which Dr. Comstock 

 accepts with certain modifications; andesites are ejected early 

 near the base of large folds ; and if the need of escape from com- 

 pression be great and long-continued, trachyte and rhyolite and 

 finally basalt may follow. He observed that existing examples 

 clearly show this sequence. The local glacial drift and the veins 

 of the region were also described. 



Tully Limestone. — S. G. Williams, of Cornell, detailed the out- 

 crop and thickness of the Tully limestone in the neighborhood of 

 the finger lakes of western New York, where its eroded margin 

 follows a sinuous line. Its gentle dip to the south is occasionally 

 varied by faint curvature in the form of very flat broad-span 

 -arches. A list of one hundred and sixteen fossils was presented 

 as representing its fauna. E. W. Claypole referred to a bed in 

 Pennsylvania that he had thought to be the equivalent of the 

 Tully limestone in New York, and believed his opinion confirmed 

 by the fossils of this list. H. S. Williams thought that nearly all 

 these fossils belonged to the calcareous Hamilton beds that oc- 

 curred near the true Tully limestone, which he regarded as poor 

 in fossils. 



Mollusca of the New Jersey Marls. — R. P. Whitfield, in a 

 paper on the molluscan fauna of the New Jersey marls, gave 

 reasons for belief that the Cretaceous members are equivalents of 

 the higher members (Nos. 4 and 5) of the upper Missouri section, 

 and that the Eocene beds are nearly coeval with the Claiborne 

 beds of the south. The distinctive features of these studies are 

 the gathering together of the material and its separation into 

 paleontological horizons corresponding with those determined 

 stratigraphically by the State geologist. The list of species 

 includes 224 Lamellibranchs, of which 74 are new, and 132 Gas- 



