Geology and Mineralogy. 163 



4. On the Joint Transmission of Direct and Alternating Cur- 

 rents. — In a paper presented before the recent meeting of the 

 American Association, Dr. Frederick Bedell discussed the 

 simultaneous transmission of direct and alternating currents by 

 the same conductor. He shows that each current acts as though 

 it had the whole conductor to itself and the other current were 

 absent. Further there results a saving in weight of copper and 

 copper losses, which saving, as shown by calculation, may amount 

 to as much as fifty per cent. 



II. Geology and Mineralogy. 



1. Geology of the Narragansett Basin ; by N. S. Shaler, J. 

 B. Woodworth and A. F. Foerste. Monograph XXXIII, 

 United States Geological Survey, pis. i-xxxi, figs. 1-30, pp. v-xx, 

 1-402, Washington, 1899. — The investigations reported in this 

 Monograph were begun as early as 1865 by Professor Shaler, at 

 first in connection with his university classes in geology. Ten 

 years ago the completion of the work for publication as a mono- 

 graph was undertaken in connection with the United States Geo- 

 logical Survey, and has been completed with the assistance of 

 Mr. Foerste, working in the southern section, and Mr. Wood- 

 worth, in the northern portion of the field. The study of the 

 construction of the basin has led to one important conclusion, 

 which requires special notice, which may be best expressed by 

 quoting the words of Professor Shaler: "The judgment as to 

 the nature of the mountain-building work rests in part upon 

 observations — in the main unpublished — which I have made in 

 other somewhat similar basins that lie along the Atlantic coast 

 from Newfoundland to North Carolina. The general proposi- 

 tion that the basins are characteristically old river-valleys which 

 have been depressed below the sea level, filled with sediments 

 — the sedimentation increasing the depth of the depression — and 

 afterwards corrugated by the mountain-building forces, will 

 derive its verification in part, if at all, from the study of other 

 troughs of the Atlantic coast. It may, however, fairly be 

 claimed that the facts set forth in this memoir show that this 

 succession of actions has taken place in the Narragansett field." 



Mr. J. B. Woodworth has written a report upon the northern 

 and eastern portion of the basin (pp. 99-214). In his report the 

 pre-Carboniferous rocks recognized are classified as follows : 

 Algonkian Period 

 Blackstone series 



Cumberland quartzites 

 Ashton schists 

 Smithfield limestones. 



Rocks of Cambrian age are recognized in drift pebbles, but not 

 in place in the northern basin. 



The rocks of the Carboniferous system are classified under the 

 following names : from below upward : 



