452 Notices respecting New Books. 



the self-induction of short pieces of wire or rod. It is now 

 generally known that the impedance in even large copper rods or 

 strips may be enormous, and that when there is a condensing 

 action and rapid discharge, great surging of electricity may take 

 place and the potential differences which may exist between 

 different parts of such rods may be enormous. The currents on 

 the outsides of conductors may fuse the metal when there is no 

 current and no heating inside. We are led to the use of round 

 rods of iron because their strength and endurance are of more 

 importance than any other qualities. The reader of this book sees 

 clearly how Dr. Lodge was led to the study of those electric 

 oscillations which Prof. Hertz began to consider a year or so 

 previously. It is good that these lectures and papers and extracts 

 from discussions before learned societies should be published in a 

 book form. Now that they are published, it would be good to 

 have a much sinaJler book published with those parts left out 

 which are merely historically interesting. 



Volcanoes, Past and Present. By Edward Hull, 31. A., LL.D., 

 l^.R.S. 270 pages, with 41 illustrations and 4 plates of rock- 

 sections. 8vo. 1892. Walter Scott, London. 

 This handy little volume is one of the " Contemporary Science 

 Series"; and, with its many nice illustrations, is intended as a 

 popular account of volcanic phenomena, their characteristics aud 

 probable causes. A bibliographic sketch of some of the chief 

 works on volcanoes and earthquakes is first given ; and is sup- 

 plemented by numerous foot-notes throughout the book. Then 

 follow some notes — on the form, structure, and composition of 

 volcanic mountains, — on the lines and groups of active volcanic 

 vents, — and on mid-oceanic volcanic islands. A condensed account 

 of the active, dormant, and extinct volcanoes of Europe forms 

 Part II. ; and those of other parts of the world are briefly described 

 in Part III. The districts in the British Islands in which volcanic 

 energy was active in the geological Tertiary period are succinctly 

 treated in Part IV. ; and in Part V. the author notices older vol- 

 canic rocks, both in other parts of the globe (India, Abyssinia, and 

 Cape Colony), and in the British Isles. The eruption of Krakatoa 

 and some earthquakes, as well as the volcanic aspect of the moon, 

 together with theoretical considerations, are referred to in Parts VI. 

 and VII. 



An Appendix offers " a brief account of the principal varieties 

 of volcanic rocks," with the four plates of "magnified sections'' 

 showing their structure. 



This little book on a large subject has been written by the pen 

 of a ready writer, who, appreciating the picturesque and the 

 wonderful, but not working up to the strict scientific standard of 

 the investigators whom he mentions at pages viii and 260, has 

 produced a somewhat dilettante sketch of the results of volcanic 



