526 



SCIENCE. 



[N. S. Vol. XIX. No. 483. 



comparable with that of the .septa in the 

 extinct forms, though proceeding in only 

 two of the six primary chambers. 



Tlie Sudbury Nickel-bearing Eruptive: 



A. P. Coleman. 



Field work carried on for two summers 

 for the Bureau of Mines of Ontario has 

 proved that the eruptive rock accompanied 

 by nickel ores in the Sudbury District has 

 a continuous outcrop enclosing an oval area 

 forty miles by sixteen in extent, and dip- 

 ping inwards on all sides. It is in reality 

 a sheet of rock from one to three miles 

 thick forming a boat-shaped basin, but 

 having an eruptive contact with the rocks 

 both above and below. Its outer, lower 

 edge consists of norite and is much more 

 basic than the inner, upper edge, which is 

 a micropegmatite consisting mainly of alka- 

 line feldspars and quartz. The nickel ore 

 bodies are found arranged along the basic, 

 outer edge or on irregular dike-like exten- 

 sions of the norite which may reach six 

 miles from the main body of the eruptive. 

 One mine contains several million tons of 

 ore. Most of the ore appears to have sep- 

 arated by gravitation from the still molten 

 eruptive, but part has been deposited by 

 circulating waters. 



The Widespread Occurrence of Fayalite in 

 Certain Igneous Bocks of Wisconsin: 

 Samuel Weidman. 



In the central part of Wisconsin, within 

 the area of pre-Cambrian rocks, is a large 

 variety and abundance of igneous rock 

 which intrudes a much older sedimentary 

 series, and, in turn, lies beneath a later 

 sedimentary series. These igneous rocks 

 may be divided into three series ; the oldest 

 being rhyolite ; the next, diorite, gabbro 

 and peridotite; the latest, granite, quartz- 

 syenite, nepheline, sodalite, and segerite- 

 syenites, and related rocks. In the last- 

 mentioned series fayalite occurs as a per- 



sistent, though minor, constituent. Anal- 

 ysis of the fayalite is given. Also analyses 

 of the rock varieties are given, showing a 

 remarkably low content of magnesia, which 

 does not increase as the content of silica in 

 the series decreases. The alteration of the 

 fayalite is to magnetic iron oxide. A brief 

 account of the general occurrence of fayal- 

 ite in other places is given. The various 

 principal types of rock from Wisconsin, 

 containing fayalite, with thin sections and 

 photo-micrographs, are exhibited. 



Stnictwal Relatione of the Granites of 

 North Carolina: Thomas Leonard Wat- 

 son. (Read by title.) 

 Describes the occurrence, distribution 

 and petrography of the North Carolina 

 granites, with special reference to their 

 structural and age relations. The numer- 

 ous dikes of basic igneous rocks penetrating 

 the crystallines of the Carolina Piedmont 

 Plateau region are discussed in their rela- 

 tions to the jointed structure of the en- 

 closing rocks, especially the granites. 



Field Work in the Wisconsin Lead and 



Zinc District: U. S. Grant. 



During the summer of 1903 the Wiscon- 

 sin Geological and Natiiral History Survey 

 did sbme detailed mapping of selected areas 

 in the southwestern portion of the state, 

 which is part of the Upper Mississippi 

 Valley lead and zinc district. In this field 

 work the topographic and geologic map- 

 pings were carried on pari passu by the 

 same individuals ; the field sheets prepared 

 were on the scale of eight inches to the 

 mile, with ten-foot contour interval, and in 

 publication the scale is to be reduced one 

 half. Wliile maps of this scale and detail 

 will be valuable in themselves, it is hoped 

 that they will give important results in 

 working out the details of the relations of 

 the ore bodies to the structure of the dis- 

 trict. 



