244 Scientific Intelligence. 



bottom by diffusion, and there causes the deposition of the stony- 

 crust by its action on the sea-water. The crust, which is chiefly 

 composed of carbonate of lime, siliceous clay, and free silica, 

 varies in thickness from about 1*5 centimetres (0*59 inches) to 8 

 centimetres (3*15 inches), and tends to obliterate the inequalities 

 of the original sea-bottom. Its upper surface is likely to be 

 smooth and clean, while the lower is in immediate contact with 

 the clayey sand. 



Dr. Natterer also draws some interesting conclusions from the 

 application of a special chemical method, based on local varia- 

 tions in the amounts of bromine, of iodine, and of nitrous acid 

 contained in sea-water, to the detection and measurement of cur- 

 rents which move too sluggishly to be amenable to direct obser- 

 vations. He has this year been able to subject his method to a 

 severe test in the currents of the JEgean, where it is possible to 

 make direct measurements for comparison ; and although the 

 results are not yet fully worked out, the two methods agree very 

 closely. Finally, with regard to the extraordinary poverty of 

 the pelagic fauna of the Mediterranean as compared with the 

 open ocean, Dr. Natterer expresses the opinion that so far as 

 chemical conditions alone are concerned, these are favorable to 

 animal life, and that as a matter of fact a rich fauna occurs in 

 some regions in the immediate vicinity of quite sterile masses of 

 water. It appears that abundant animal life is present just 

 where the water is in rapid motion ; and that, generally, the 

 poverty of the Mediterranean fauna is largely due to the want of 

 circulation in its waters— a result opposed to that of Carpenter, 

 who believed it to be due to the excess of suspended matter." — 

 The Geographical Journal, vol. iii, pp. 138-140. 



2. Electric Waves/ being Researches on the Propagation of 

 Electric action with finite velocity through Space. By Dr. Hbin- 

 rich Hertz, Professor of Physics in the University of Bonn. 

 Authorized English Translation by D. E. Jones, B.Sc. With a 

 Preface by Lord Kelvin, LL.D., D.C.L. 8vo, pp. xviii, 280. 

 London and New York, 1893 (Macmillan & Co.). — Probably no 

 greater step in experimental science has been taken in modern 

 times than that which was announced by Dr. Hertz in the spring 

 and summer of 1888 proving the finite velocity of propagation of 

 electromagnetic actions, and showing that these electromagnetic 

 waves in air represent " on a million-fold larger scale the same 

 processes which go on in the neighborhood of a Fresnel mirror or 

 between the glass plates used for exhibiting Newton's rings." 

 The remarkable series of papers in which these discoveries were 

 announced were so much in demand that the publishers of 

 Wiedemann' 's Annalen, in which they appeared, invited him to 

 prepare them for separate publication. This he did under the 

 title : " Untersuchungen iiber die Ausbreitung der Elektrischen 

 Kraft," adding an introduction and supplementary notes. This 

 admirable book now appears in an English dress ; and will be 

 warmly welcomed by English-speaking men of science. Its ap- 

 pearance was almost simultaneous with the death of its brilliant 

 author, Dr. Hertz having died iu Bonn on January 1st, 1S94, at 

 the early age of 37. G. F. b. 



