482 Scientific Intelligence. 



stations in Eastern Canada and the United States, will probably 

 be affected by the penumbra in the early morning. At Montreal 

 the eclipse (partial) is at its greatest phase at 5.52 a. m. Standard 

 time. It is possible that the eclipse may have some influence 

 even when it is invisible. 



" The investigation of strays is of as great interest as that of 

 signals. So far as is yet known, the natural electric waves reach- 

 ing wireless telegraph stations in latitudes higher than 50° appear to 

 travel mostly from the south. Thus the greatest changes produced 

 in strays by the eclipse will probably be experienced at stations 

 in Scandinavia and Russia, to reach which the waves must cross 

 the path of the umbra. At the same time changes of some kind 

 are to be expected in other districts than these, and it is therefore 

 desirable that statistical observations of natural electric waves be 

 made all over the world, and especially at places within an earth 

 quadrant of Southern Russia. It is also desirable that meteoro- 

 logical observations, including those of atmospheric ionization and 

 potential gradient, should be at the disposal of the committee 

 Avhen considering the records of strays and signals. 



" The committee propose to prepare and circulate special forms 

 for the collection of statistics of signals and strays, especially 

 within the hemisphere likely to be affected by the eclipse ; they 

 will endeavour to make provision for the transmission of special 

 signals at times to be indicated on the forms ; and they will offer 

 for the consideration of the authorities controlling stations near 

 the central line a simple programme of work. The discussion of 

 the observations, and the comparison with meteorological data, 

 will be carried out by the committee ; and digests of the statistics, 

 together with the conclusions drawn from the analysis, will be 

 published in due course. 



" The committee would be greatly aided in the organization of 

 this investigation if those possessing the necessary facilities and 

 willing to make observations during the eclipse would com- 

 municate with the Hon. Secretary, Dr. W. Eccles, University 

 College, London, W. C, at the earliest possible date." 



II. Geology and Natural History. 



1. Manual of Petrographic 3Iethods, by A. Johannsen. 

 Pp. xxviii, 649, 8°, figs. 764. New York, 1914 (McGraw 

 Hill Book Co.). — This work, as its name implies, is not a text- 

 book for beginners in petrology, but a volume of reference for 

 workers of all classes in the subject. It is in some ways the most 

 complete work of its kind that has yet appeared, containing more 

 methods and material than even the first volume of the last 

 edition of Rosenbusch's Physiographie. Every part of the pedog- 

 raph er's laboratory equipment, excepting of course that required 

 in analytical chemical operations, is fully described, not only 

 from the practical but also from the theoretical standpoint. The 

 treatment of crystals both on the crystallographic and optical 



