480 



NATURE 



[June 17, 1920 



allowed to escape through the meshes of the 

 author's critical net, but he is apparently not con- 

 cerned with the prevalent yet distracting use of the 

 word "gradient" to mean rate of loss per unit 

 length either in the vertical or horizontal direction 

 when speaking of temperature. In this country we 

 are becoming accustomed to confine the word 

 " gradient " to what is commonly understood when 

 it is used with pressure, and to use " lapse " for 

 vertical changes, which are normally losses, with 

 increasing height. 



As readers of Nature already know, it is part 

 of Prof. McAdie's "credo" that pressure should 

 be expressed in "kilobars," which are now com- 

 monly known as "millibars," and that temperature 

 should be expressed in new absolute units of which 

 1000 go to 273 degrees of the Centigrade scale. 

 In the reviewer's experience of units the whole 

 world is divided into three very unequal parts. 

 By far the largest part is made up of persons who 

 think that absolute units for practical concerns are 

 obviously impossible because the man in the street 

 does not " understand " them at all ; the next 

 largest of those who think that absolute units 

 in practice are quite unnecessary because any 

 competent man of science fully understands them 

 and can make the transition whenever he requires 

 them ; and the third is a small body of persons 

 who are devoted to their use because the scientific 

 future of meteorology lies that way. To change 

 once more the already changed in order to remove 

 an apparent historical inconsistency conveys no 

 promise of ranging the well-informed minority on 

 the side of progressive action, but would hand 

 us over helpless to the judgment of the great 

 majority who do not "understand," and who are 

 obsessed with the idea that scientific results are 

 naught if they cannot be used without thinking. 



Among the excellent illustrations of the book 

 are some photographs of cloud-forms. Its author 

 is very insistent that Luke Howard's classifica- 

 tion of cloud-forms on the basis of appearance, 

 as extended by the international conferences, is 

 wrong in principle. He thinks they should be 

 classified according to origin. Unfortunately, the 

 appearance is all that an observer can record, and 

 to ask the ordinary observer to differentiate between 

 similar appearances according to some general 

 instruction as to origin would add materially to 

 the difficulties of the student. What is most 

 wanted is some effective means for the individual 

 observer to ascertain the height of the cloud which 

 he sees. Some simple form of range-finder for 

 clouds suitable for the chief observatories ought 

 not to be beyond the limit of possibility. 



The book comes from Blue Hill Observatory, 

 now a part of Harvard University, and contains 

 NO. 2642, VOL. 105] 



much incidental information as to the great 

 services which that establishment has rendered 

 to meteorology. Its many friends and admirers 

 in this country will welcome the attempt of its 

 present chief to set out the leading principles of 

 aerography which the observatory has done so 

 much to elucidate. * 



Paper-making and its Machinery. 



Paper-making and its Machinery : Including 

 Chapters on the Tub-sizing of Paper, the 

 Coating and Finishing of Art Paper, and the 

 Coating of Photographic Paper. By T. W. 

 Chalmers. (The Engineer Series.) Pp. xi-f- 

 178 + vi plates. (London: Constable and Co., 

 Ltd., 1920.) Price 26s. net. 



THE author in his preface has rightly stated 

 that the chemist interested in paper-making 

 finds ample technical literature at his disposal, 

 whereas the engineer is not provided with any 

 books dealing with the peculiar mechanical prob- 

 lems of his industry. Since the publication of 

 Hofmann's treatise on "The Manufacture of 

 Paper " in 1873 no serious attempt has been made 

 to supply the paper-maker with an intelligent and 

 comprehensive text-book devoted to a study of 

 the economic and efficient control of the machinery 

 peculiar to the manufacture of paper. 



Mr. Chalmers's effort in this direction, admir- 

 able as it is, regarded in its proper aspect as a 

 pioneer to some such technical treatise, falls far 

 short of our expectations in this direction. It 

 is doubtful whether a really practical and useful 

 text-book on the engineering problems of the paper 

 industry will ever be written. The utility of the 

 book we have in mind will depend on a free and 

 frank exposS, by an engineer thoroughly ac- 

 quainted with the art and practice of paper- 

 making, of.conditions, methods, economics, power 

 costs, capacities, output, means for overcoming 

 difficulties, and the hundred "wrinkles" born of 

 long apprenticeship. The description of paper- 

 machines and subsidiary appliances, essential as 

 it certainly is, constitutes only one part, and that 

 the minor part, of an ideal manual. 



The causes which have contributed to this lack 

 of information may be traced to the somewhat 

 natural reluctance on the part of a practical en- 

 gineer to " give away " his knowledge. Every 

 engineer fondly believes he has a monopoly of 

 this kind, and the difficulty of shaking him from 

 such an idea may fully account for the absence of 

 a text-book which would be gladly welcomed by 

 the trade. We may therefore reasonably hope that 

 the present work will inspire some paper-maker 

 to write a supplement. 



