May 15, 1903.J 



SCIENCE. 



793 



ated and even shaly, resulted in the lateral 

 movement being taken up in varying degree 

 by the individual beds, so that the motion 

 was such as is produced by forces acting in 

 couples. The brecciation is due to the tend- 

 ency of the pieces, resulting from the break- 

 ing of certain brittle strata, to shear past each 

 other, or to rotate with the horizontal move- 

 ments of the adjacent beds, so that the frag- 

 ments are relatively displaced. 



Mr. E. 0. Eckel, 'Dahlonega Mining Dis- 

 trict, Georgia.' 



The country rocks in the Dahlonega dis- 

 trict in Georgia are mica schists and gneisses 

 of pre-Cambrian age, including possibly some 

 m.etamorphosed Paleozoic. These early rocks 

 are cut by diorites and granites; the former 

 highly sheared, the latter but slightly gneiss- 

 oid. The gold-bearing quartz veins occur 

 along the contacts of the diorites or granites 

 with the mica schists. The veins show but 

 little deformation, and the epoch of vein 

 formation, as well as of the intrusion of the 

 granites, is therefore thought to be not earlier 

 than the Ordovician. This view is confirmed 

 by the occurrence of gold veins in the Ocoee 

 (Cambro-Silurian) rocks of Georgia and Ten- 

 nessee, and in Ordovician rocks in New York. 

 W. 0. Mendenhall, 

 Secretary. 



NEW YORK ACADEMY OF SCIENOE. SECTION OF 

 GEOLOGY AND MINERALOGY. 



A REGULAR meeting of the Section of Geol- 

 ogy and Mineralogy was held at the American 

 Museum of Natural History on the evening 

 of March 16. In the absence of Professor 

 Kemp, Dr. Julien was made temporary chair- 

 man. 



The first paper was by Dr. A. W. Grabau 

 on the ' Geology of Becraft Mountain, New 

 York.' Becraft Mountain, in Columbia Co., 

 N. Y., is an outlier of the Helderberg Moun- 

 tains. Its base is formed by the upturned 

 and eroded rocks of the Hudson Group, chiefly 

 the Norman's Kill shales. Unconformably 

 upon this rests the upper part of the Manlius 

 limestone, followed in turn by the members 

 of the New York Devonian up to and includ- 



ing the Onondaga limestone. The structure 

 of the eastern and southern portion of the 

 mountain, which is of the Appalachian type, 

 was discussed, and the excessive folding and 

 faulting upon it illustrated by maps and sec- 

 tions. The paper was discussed by Dr. Ste- 

 venson and by Dr. Julien. 



The second paper, by Mr. C. W. Dickson, 

 was entitled 'The Mineralogy and Geology 

 of the Sudbury Ontario Copper Nickel De- 

 posits.' 



It was shown that by magnetic concentra- 

 tion of the ore nearly all the nickel can be 

 eliminated from the pyrrhotite, proving that 

 the element is present in a separate mineral 

 and that it does not replace part of the iron 

 of the pyrrhotite isomorphously. The eco- 

 nomic concentration of the nickel by mag- 

 netic methods is, however, practically impos- 

 sible. The composition of the nickel mineral 

 corresponds closely to that of pentlandite, but 

 there is always an excess of (Fe-j-Ni) over 

 that required by the formula (Ee-f Ni)S in 

 the proportion 11 : 10. 



After studying the relations of the ore and 

 rock minerals in the field and by the aid of 

 the microscope, the conclusion was reached 

 that the deposits are replacements along 

 crushed zones through which the mineral- 

 bearing waters circulated, and that they can 

 not be original magmatic segregations, as 

 generally held. 



George I. Finlay, 

 Secretary pro tern. 



ELISHA MITCHELL SCIENTIFIC SOCIETY. 



The 148th meeting was held in the chemical 

 lecture room. University of North Carolina, 

 April 14, 7:45 p.m. 



The following papers were read: 



' The Prices of Anthracite Coal in the 

 United States, 1850-1902,' by Professor C. L. 

 Eaper. 



'Habits of North Carolina Woodpeckers,' 

 by Mr. Ivey E. Lewis. 



' Note on Imaginary Boots of a Cubic,' by 

 Professor "Wm. Cain. Certain characteristics 

 of the graphs of functions of the third degree 

 were established and easy tests found (not 



