Feb. 2, 1888] 



NATURE 



315 



upon zinc ; (2) by means of caustic potash and alu- 

 minium ; and (3) by electrolysis. In all, sixteen experi- 

 ments are given. The results are stated in the following 

 table :— 



The final mean is O =r o"ooi7. 



This very bald account does but scanty justice to the 

 beauty and simplicity of the methods adopted by Prof. 

 Cooke and Mr. Richards, and to the manipulative skill 

 and patience with which they carried them out. With 

 respect to the bearing of their result on Prout's hypothesis, 

 the question seems to them to narrow itself to this point : 

 Is the hydrogen they have made use of the typical hydrogen 

 element ? They are inclined to believe that the theoretical 

 question in regard to Prout's law has been settled so far 

 as analytical work can solve the problem. On this point, 

 however, we are at issue with them. That statement 

 impHes a finality about our present quantitative methods 

 which we have no right to assume. It implies, too, that 

 the methods employed by the authors have yielded as close 

 an approximation to the typical element as we are ever 

 likely to obtain. Their method in principle no doubt 

 removes one fundamental objection to Dumas' plan of 

 work, considered as an experimental process, but it by no 

 means removes all the sources of error, and anybody who 

 will patiently sift out these sources and seek to appreciate 

 their net effect must admit that the ultimate tendency 

 is to apparently lower the relative value of the atomic 

 weight of oxygen. 



If we have regard to this fact, and if we consider too 

 what we may call the volumetric evidence, as given above, 

 it seems premature to assume that the ultimate question 

 has actually been narrowed down to the point to which 

 Prof. Cooke and Mr. Richards are disposed to conclude 

 that they have brought it. T. E. THORPE. 



PHYSICAL GEOGRAPHY OF THE SEA. 

 Handbuch der Ozeanographie. Von Dr. Georg von 



Boguslawski und Prof. Dr. Otto Kriimmel. Two 



Vols. (Stuttgart: Engelhorn, 1884-87.) 

 'T^HESE volumes belong to a series of geographical 

 -•- hand-books — each written by an acknowledged 

 master of the subject — brought out on a uniform plan 

 under the editorship of Prof. Dr. F. Ratzel, by the 

 well-known Stuttgart publishing firm of Engelhorn. 



Dr. Ratzel's own volume on Anthropogeography, Dr. 

 Hann's on Climatologj'^, and Dr. Heim's on Glaciers 

 have already appeared ; and now, under the somewhat 

 novel name of " Oceanography," the physical geography 

 of the sea has been exhaustively treated. The editor 

 has divided the subject into two parts, and given each to 

 a specialist. In Volume I., Prof. Dr. G. von Boguslawski, 



of the Hydrographical Department of the German Ad- 

 miralty, treats of the distribution, physical condition, and 

 chemical composition of sea- water ; while in Volume II., 

 Dr. Otto Kriimmel, Professor of Geography in the Uni- 

 versity of Kiel, discourses on the motions of the ocean. 

 Each part is complete in itself, but the index to both is 

 given only in the second volume. 



It is somewhat difficult to give an idea of the multi- 

 farious contents of this exhaustive treatise. In Volume I., 

 Dr. Boguslawski begins with an account of the shape 

 and area of the different oceans, and then naturally de- 

 scribes successively the physical character of their various 

 coast-lines, and the depths of the sea all over the world. 

 But we must remark on the poverty of illustration and the 

 absence of maps which characterize this and so many 

 other first-rate German books. Here we have actually 

 no map, however rough, to show graphically the depth of 

 the oceans. The unfortunate reader who wants to get 

 his information as easily and quickly as possible has first 

 to read through about 100 pages of closely-printed type, 

 and then to try and picture to himself the relief of the 

 floor of the sea. 



After discussing ocean depths, the author devotes a 

 short chapter to the chemical composition of salt water ; 

 and then a somewhat longer space to the density or 

 specific gravity of the sea. Colour and transparency are 

 next discussed, and the last 200 pages are occupied with 

 what is called maritime meteorology. 



Of this space only thirty-four pages are devoted to wind 

 and storms, and very rightly, as these subjects would re- 

 quire a special volume for their proper treatment. The 

 remainder is occupied with a minute account of the tem- 

 perature of the ocean, both on the surface and at various 

 depths ; and with a notice of the distribution of ice in 

 high latitudes. Here too, the value of the admirable text 

 is greatly diminished by the absence of maps. 



So far no mathematics have been required, but it is 

 impossible to treat of the motions of the sea without 

 algebraical formulae. Dr. Kriimmel, however, uses great 

 judgment in only giving the formulae of motion, which 

 only involve simple algebra, and not the investigation of 

 the formulae, that would require much higher analysis. 



In the second volume he begins with the consideration 

 of waves. The theory of wave-motion, both in deep and 

 shallow water, he gives first, mostly following Airy ; while 

 experimental illustrations, and observations on the actual 

 length, height, and speed of waves follow next. Breakers 

 and rollers are then discussed, together with their in- 

 fluence on the abrasion of coast-lines. Earthquake and 

 volcanic- waves are illustrated by a self-recorded tidal 

 trace from South Georgia, which will be new to Enghsh 

 readers ; and the section ends with a capital account of 

 stationary waves, seches, and of the curious tidal pheno- 

 mena in the Straits of Euripus, which so puzzled the 

 ancient Greeks. 



The author then turns to tides, dealing mostly with 

 the theories of Laplace, Whewell, Ferrel, Airy, Thom- 

 son, &c., but very wisely ending with a chapter on 

 "unsolved problems." The difficult subject of the ver- 

 tical circulation of the ocean is next discussed, and an 

 admirable account given of the cold aufreibwasser — 

 up-rubbed water — of tropical weather coasts. This un- 

 euphonious term is applied to the cold water that is found 



