482 SCIENCE PROGRESS 



The usefulness of chemistry in this connection has long been directly obvious 

 and that science is well provided with comprehensive reference-books ; but 

 the work of the physicist has usually reached the industrial world by way 

 of the engineer, so that physics has long been regarded as rather an academic 

 science out of touch with human needs : indeed, since for that very reason 

 the physicist rarely came into contact with industrial conditions, it inevitably 

 tended in that direction. The war altered all this, and one of its few beneficial 

 results has been the recognition, by at least a small part of the manufacturing 

 interests of the country, that the physicist is able to give valuable assistance 

 in the solution of many of the technical problems of industry. With that 

 recognition has come a new grouping of scientific knowledge, a combination 

 of physics and engineering in which the former is the dominant partner, and 

 it is with this grouping that the volumes under review are mainly concerned. 

 Realisation that the works chemist has need of some knowledge of engin- 

 eering has already resulted in the provision of college courses in chemical 

 engineering ; it is to be hoped that the time is not far distant when similar 

 training will be available for the physicist. 



The Dictionary has been arranged so that those interested in only one or 

 two branches of physics need not purchase the complete work in order to 

 cover the whole of the ground with which they are concerned. The arrange- 

 ment in each volume is alphabetical, but the volumes themselves deal with 

 specific parts of the subject. The contents of the first two volumes have 

 already been indicated ; Vol. Ill will contain the articles on Meteorology, 

 Metrology, and Measuring Apparatus ; Vol. IV those on Optics, Sound, and 

 Radiology ; and Vol. V those on Metallurgy and Aeronautics. In order that 

 each volume may be complete, a certain amount of overlapping has been 

 admitted, e.g. Vol. I contains a complete account of the instruments used 

 for measuring pressure and temperature (including the Resistance Thermo- 

 meter and Thermocouples), which might perhaps have been looked for under 

 Measuring Instruments, while Vol. II contains an article on X-rays which 

 will no doubt be amplified in the volume on Radiology. This subdivision 

 of the subject-matter in separate volumes, while greatly to the advantage 

 of the limited purse of the average physicist, is presumably also responsible 

 for some of the few, but conspicuous, lacunae in the volumes already published. 

 Thus in Vol. I there is no reference to hygrometry, and Vol. II gives no in- 

 formation about electroscopes, machines for generating static electricity, 

 the ordinary induction coil, or any kind of medical application of electricity. 

 There are other omissions which can hardly be repaired elsewhere — notably 

 in connection with those subjects studied under the head of general properties 

 of matter, such as surface tension, diffusion, osmotic pressure, and the kinetic 

 theory. 



The authors of the great majority of the articles have a first-hand know- 

 ledge of the subjects on which they write. This is essential in an authoritative 

 work, but, when space is limited, is apt to lead to a biased choice of material. 

 In these articles such bias is remarkable for its absence, where it occurs 

 the omissions may be defended on the ground that the practical side of the 

 subject is to have preference. A surprisingly large proportion of the material 

 appears in book form for the first time, having been collected from widely 

 scattered and often extemely inaccessible papers. Articles notably rich 

 in information of this character are those on Air-pumps (by the Research 

 Staff of the General Electric Co.) ; Calorimetry (Ezer Griffiths) ; Heat 

 Convection (F. H. Schofield) ; Friction (T. E. Stanton) ; Viscometry (W. 

 F. Higgins) ; and the Realisation of the Absolute Scale of Temperature, 

 a very notable essay by Day and Sosman. 



The plan adopted by most of the writers of the longer articles is to give 

 a general introduction, and then, under suitable headings, an account of the 

 methods employed in the most important researches, with diagrams of the 



