450 



NATURE 



[June 9, 192 1 



compartments containing homogeneous material, 

 and (b) compartments which admit freely 

 any literary matter of sufficient merit or popular 

 appeal. The problem, therefore, is to devise a 

 scheme by which information contained in the 

 latter class — for class (a) presents no special diffi- 

 culties — can be made to flow towards its proper 

 recipient, and this, obviously, can be effected 

 economically only by the acceptance of a common 

 system of classification. 



So far as the literature of science is concerned, 

 a classification already exists in the scheme 

 adopted by the " International Catalogue of 

 Scientific Literature." This scheme has been 

 incorporated in that of the Library of the 

 L'nited States Congress — a library the staff 

 of which appears to possess special quali- 

 fications for dealing with the literature of the exact 

 sciences. Further, this scheme has been published 

 in two forms : (a) with its headings arranged in 

 class order and. issued in separate sections, e.g. 

 Q = science in general [QA = mathematics, and so 

 forth] ; and (b) with its headings arranged in one 

 general alphabet. Thus science possesses a classi- 

 fication stamped with its own hall-mark, but 

 grafted on to a scheme for the general classifica- 

 tion of knowledge. Still, the acceptance of the 

 Library of Congress classification is not an essen- 

 tial feature of these proposals, which are based on 

 the recognition (i) of the division of periodical 

 literature into (a) the homogeneous and (b) the 

 non-homogeneous classes ; (2) of the economic ad- 

 vantage of dealing on a co-operative basis with 

 the latter ; and further, since the non-homogene- 

 ous periodicals cover all departments of know- 

 ledge, (3) of the necessity of adopting some agreed 

 system of classification for the purpose of estab- 

 lishing a means of exchange between the different 

 interests. 



Thus we have shown that the core or 

 umbra of a subject is comprised in a body of 

 homogeneous literature which unquestionably can 

 best be dealt with by its representative professional 

 society, but that outside this core there exists a 

 penumbra of relevant matter dispersed through a 

 literature of gradually increasing irrelevance, 

 with the result that the recovery of the relevant 

 matter can be effected economically only by co- 

 operative effort. The solution, therefore, would 

 appear to be to bring into existence a Central 

 Bureau which should deal solely with the indexing 

 of periodicals of the non-homogeneous character 

 — and in the first stages of its work, with a re- 

 stricted list of periodicals assigned to it by the 

 NO. 2693, VOL. 107] 



contributory bodies. These bodies would receive 

 from the Central Bureau entries from the peri- 

 odicals examined corresponding to their specified 

 requirements. But as the professional abstracts 

 became more fully representative of progress in 

 their respective fields the need for the publication 

 of the corresponding indexes would tend to dis- 

 appear. The institution, therefore, of a Central 

 Bureau would ultimately make for economy in all 

 branches of science in which the publication of 

 abstracts is admittedly indispensable. 



So far as science is concerned, it will probably 

 be found that the simplest and most effective 

 method for obtaining the necessary index slips 

 would be to invite the Central Bureau of the 

 " International Catalogue of Scientific Literature " 

 to provide them. Indeed, the possibility of co- 

 operation between the " International Catalogue " 

 and the abstracting journals was one of the sub- 

 jects considered at the conference held last Sep- 

 tember. Any such arrangement would probably 

 begin with the year 192 1, and, as a preliminary, 

 the " International Catalogue " should be brought 

 up to date by the publication of volumes for 

 1915-20. The provision of funds for this purpose 

 is an urgent necessity, as explained in Nature 

 for October 7, 1920, vol. cvi., p. 195. 



In the foregoing observations we have assumed 

 that the proper bibliographical equipment of the 

 sciences will in the main be founded upon the 

 possession of adequate abstracts. But if the sub- 

 ject were threshed out in an open conference at 

 which representatives of all branches of knowledge 

 were invited to attend, this proposition would not 

 be accepted as holding good universally. Some 

 branches would probably prefer periodical critical 

 reviews or summaries of the year's progress, 

 while others would be content with alphabetically 

 arranged index entries. Our final proposal, there- 

 fore, is that such a conference should be held in 

 order that the special requirements of each 

 division of knowledge should be authoritatively 

 ascertained, and the feasibility of co-operative or 

 co-ordinated action discussed. 



Piezo-chemistry. 



Piezochemie kondensierter Systeme. By Prof. E. 

 Cohen and Dr. W. Schut. Pp. ix + 449. (Leip- 

 zig : Akademische Verlagsgesellschaft m.b.H. : 

 Gustav Fock, 1919.) 



THE direction and extent of a physical or 

 chemical change are frequently determined 

 or modified by pressure. This fact has long been 



