Maech 6, 1896.] 



SCIENCE. 



375 



and low latitudes, in the former meclianical 

 agencies prevailing, and in the latter chemical. 

 Notes on the Geology of the San Carlos Coal Held, 



Trans-Pecos, Texas. By T. WaylAND Vau- 



GHAN. 



The author gave the results of a reeonnois- 

 sance made jointly with Mr. T. W. Stanton, of 

 the U. S. Geological Survey, during the field 

 season of 1895. The coal field is situated in the 

 Veija Mountains. Some general observations 

 on the structure and topographic features of the 

 region were made. Two detailed sections of 

 the mountains were described. The general 

 features of the combined sections, beginning at 

 the top, are: 



3. A massive lava-flow of quartz-pantellerite, 

 which forms the summit of the mountains and 

 from 400-600 feet thick. 



2. A series of interbedded massive and frag- 

 mental rhyolites and conglomerates, sandstones 

 and clays, into which a sheet of basalt has been 

 intruded. South of Chispa this series is about 

 fifteen hundred feet thick, but it is not so thick 

 at San Carlos, where there is not such a variety 

 of volcanic products. 



1. Alternating beds of sands and clays — at 

 San Carlos about fifteen hundred feet thick — 

 and in which the coal occurs. Vertebrate fos- 

 sils of Cretaceous age were found in the sand- 

 stones and clays above the coal. Below the 

 coal a rich invertebrate fauna was collected, 

 whose age was determined by Mr. Stanton to be 

 Pierre (in the terminology of the "Western 

 Interior Region) or Taylor (in the terminology 

 of the Texas Region). The age of the coal was 

 determined to be Pierre or Taylor, as Mr. E. 

 T. Dumble had previously shown. About seven 

 miles southwest of Chispa a fault was described 

 by which the Benton shales had been carried 

 down below limestone belonging to the Freder- 

 icksburg division (of the Lower Cretaceous). 

 The Benton shales are thinly laminated, bluish, 

 calcareous shales, and contain Inoceramus labi- 

 atus, a fossil characteristic of the Benton. These 

 shales are underlaid by a hard blue limestone, 

 containing Alectyonio, carinata, which is char- 

 acteristic of the Washita division. The Dakota 

 sandstone is absent. Limestone belonging to a 

 lower horizon of the Washita division was found, 

 beneath which was a limestone containing a 



fauna characteristic of the Fredericksburg divi- 

 sion. 



Dr. E. C. E. Lord followed Mr. Vaughan's 

 paper on the general geologic features of the 

 regiqn with a petrographic description of the 

 rocks collected. The rock types were : 



1. Massive rhyolite. 

 la. Rhyolite breccias. 



2. Quartz-pantellerite, which was described 

 from America for the first time. 



3. Basalt. Wm. F. Moesell. 



GEOLOGICAL CONFERENCE OF HARVARD 

 UNIVERSITY, FEBRUARY 11, 1S96. 



On the Geological Work of Vortices and Eddies, 



by T. A. Jaggar, Jr. 



A vortex occurs wherever a fluid current is 

 retarded or deflected. The properties of such 

 movements have been worked out mathemati- 

 cally by Helmholtz and others ; the present 

 writer's aim is to express in simple terms the 

 application of their results to geology, and to 

 demonstrate it experimentally. Mention was 

 made of the importance of vortical movement 

 in the study of meteorology, the flight of birds, 

 oceanic currents, dune formation, snow drift 

 and neve sculpture ; and a series of experiments 

 was exhibited with specially devised projection 

 apparatus. A horizontal beam of light projected 

 to the screen through narrow glass tanks served 

 to show Bjerknaes' beautiful experiment with 

 vortex rings, the actual development of ripple- 

 drift on a sandy surface in cross-section, the 

 growth of ripplemark and some imitative beach 

 marks. Apparatus for bending the beam up- 

 ward through glass-bottomed trays showed the 

 gradual separation of the linear sand ridges 

 under the influence of the ripple-forming vor- 

 tices in both rippledrift and ripplemark, and at- 

 tention was called to the possibility of experi- 

 mentally illustrating the action of coastal eddies 

 in building cusps. 



To be published in the proceedings of the 

 Boston Society of Natural History. 



T. A. Jaggar, Jr, 

 Recording Secretary. 



THE ACADEMY OF SCIENCE OF ST. LOUIS. 



At the meeting of February 17, 1896, Dr. 

 Adolf Alt spoke of the anatomy of the eye, and 

 by aid of the projecting microscope exhibited 



