5o6 



NA TURE 



[April 2, 1908 



surrounding- matter, and immediately pass into ad- 

 jacent atoms. This view materially reduces the num- 

 ber of corpuscles required for the transfer of elec- 

 tricity. In both these forms of theory the atoms of 

 the metal itself are supposed immobile, and to play 

 nu direct appreciable part in the transfer of the 

 current. 



The important question of the type of radiation to 

 be expected from a metal on the above theories is fully 

 considered. Since the corpuscles are suddenly started 

 and stopped, they must radiate energy in the form of 

 thin pulses analogous to the pulses which are sup- 

 posed to constitute the Rontgen rays. Lorentz has 

 shown that if this radiation be analysed by means of 

 Fourier's series, the amplitude of the long waves 

 agrees closely with that deduced independently of such 

 assumptions by means of the thermodynamical 

 theory. Prof. Thomson, however, points out that 

 the main radiation must consist of short waves 

 analogous to very easily absorbed Rontgen rays. It 

 would be of great interest and importance if the 

 presence of such a type of radiation from metals could 

 be experimentally detected. In another chapter the 

 author explains the construction and properties of his 

 well-known " model " atoms built up of rings of 

 rotating corpuscles. No one can fail to admire the in- 

 genuity displayed in the construction of such atoms, 

 and in showing the remarkable way in which they 

 imitate many of the known properties of the atom. 

 On this hypothesis the properties of the atom are 

 dependent on the number and arrangement of the 

 negative corpuscles. The corresponding positive elec- 

 tricity, which is distributed throughout the volume of 

 a sphere, merely serves as a cement to hold the atom 

 together. This form of atom, while it has many ad- 

 vantages from the point of view of calculation, is 

 somewhat artificial, for it implicitly assumes very 

 peculiar properties for the positive electricity. To say 

 that a positively charged body is one that has lost 

 a negative corpuscle is not an explanation, but begs 

 the question of the nature of positive electricity. The 

 trend of modern views is to diminish in some direc- 

 tions the importance of the negative charge and to 

 emphasise that of the positive. This is borne out by 

 the author's estimates that the number of free cor- 

 puscles in an atom is about the same as its atomic 

 weight in terms of hydrogen. Until we have a clearer 

 idea of the nature of positive electricity we cannot 

 hope to form a clear view of the constitution of the 

 atom. The proof of the existence of a positive electron 

 — the counterpart of the negative — if such exists, 

 would be of enormous importance to theory and ex- 

 periment. The problem of the nature of positive elec- 

 tricity is now very much to the fore, and it is to be 

 hoped that we shall not have to wait too long for a 

 solution. 



Like all Prof. Thomson's books, the present volume 

 is lucidly and simply written, while the mathematical 

 analysis required for the development of the con- 

 sequences of the theory is made as simple as possible. 

 To all those interested in the latest views of the con- 

 nection between electricity and matter this book will 

 be very welcome. E. R. 



NO. 2005, VOL. 77] 



CHARTING THE WORLD'S COMMERCE. 



Atlas of the World's Commerce. Compiled from the 

 Latest Official Returns at the Edinburgh Geo- 

 graphical Institute, and edited by J. G. Bartholo- 

 mew. (London : G. Xewnes, Ltd.) Twenty-two 

 parts, each 6d. net. 



MR. BARTHOLOMEW is a skilled hand at map- 

 making, and in setting himself to chart the 

 commerce of the world he has undertaken a gigantic 

 task. With the aid of 176 large pages of coloured 

 plates, containing more than 1000 maps and diagrams, 

 he attempts to describe the products, imports, exports, 

 commercial conditions and economic statistics of all 

 the leading countries of the world, and he says quite 

 justly that the successful accomplishment of such a 

 work must throw much needed light on the solution 

 of the great problem of international trade which we 

 in British politics call "the fiscal question." His 

 first object is to show whence we derive our food, 

 drink, clothing, and all that we use in our daily lives. 

 No better text could be chosen for the enlightenment 

 of our politicians, whatever be their fiscal views, and 

 indeed of all who would understand where England 

 really stands in the world of commerce, and what are 

 the essentials of her future as the central force of a 

 great Empire. 



The very immensity of Mr. Bartholomew's under- 

 taking tends to lessen its topical value. For instance, 

 the last three years have been momentous in their 

 effect upon the sources of British food supply, and 

 Mr. Bartholomew can be of little help to the man 

 who would understand how far we are dependent upon 

 foreign and how far upon colonial supplies, when he 

 only carries us down to the year 1903. Canada, for 

 instance, figures in Mr. Bartholomew's diagrams as 

 yielding less than 86 million bushels of wheat. The 

 produce of her western section alone was in igo6 

 considerably in excess of that figure. The fiscal con- 

 troversy is especially associated with the food produc- 

 tion of the newer countries, and the usefulness of Mr. 

 Bartholomew's diagrams, so far as the fiscal con- 

 troversy is concerned, goes little beyond the course of 

 our dependence upon the older countries, such as the 

 United States, Russia, &c. For his distribution of the 

 chief sources of the British supply of wheat, Mr. 

 Bartholomew brings us no further down than the 

 1901-3 average, from which we see that the Canadian 

 percentage was 8'4 and the United States percentage 

 43'5. The limited usefulness of such figures is evident 

 when it is noted that in 1906 the Canadian proportion 

 was at least 12J per cent, and the United States 

 proportion 37 per cent. There may have been in- 

 superable difficulties in carrying the averages down to 

 a more recent period, but it is obvious that, in the 

 absence of more recent figures, it is necessary to 

 endorse with qualification Mr. Bartholomew's claim 

 that in his new atlas " the whole fiscal question is 

 clearly illustrated." 



We may note one other respect in which the topical 

 usefulness of Mr. Bartholomew's investigations is 

 limited, and it is a vital one. In dealing with the 

 import and export trade of the United Kingdom 



