478 



NATURE 



[January 8, 1920 



Technologic Paper No. 139 of the Bijreau of 

 Standards, Washington, U.S.A., contains an account 

 of tests of light aluminium casting alloys, .^mong 

 other tests, a number were carried out to determine 

 to what extent the mechanical properties of cast alloys 

 could be improved by heat treatment as follows :■ — 

 Heating- for two hours at 500° C, following by 

 cooling in air, the specimens then being left to age 

 several days before testing. Some thirty sjjecimens 

 were so treated, and in all but five or six cases there 

 was a resulting increase in tensile strength of from 

 5 to 50 per cent. In cases where the heat treatment 

 showed a decrease in strength, the whole group of 

 bars of the heat was of inferior quality, cast and 

 heat-treated ones alike. The hardness was increased 

 by the heat treatment. The effect on elongation was 

 more erratic, but in general a decreased elongation 

 was found in the heat-treated specimens. It would 

 appear that the treatment of light aluminium castings 

 has commercial possibilities. Copies of the paper 

 may be obtained by addressing a request to the 

 Bureau of Standards. 



The Technical Book Review Index issued by the 

 Carnegie Library at Pittsburgh, U.S.A., appears 

 quarterly, and is a useful guide to new books on 

 pure and applied science. ITie compilers have not 

 had the actual books before them while preparing the 

 index, but have obtained their information entirely 

 from reviews that have appeared in scientific and 

 technical journals. The accuracy of the information 

 given depends therefore, in each case, upon the care 

 taken in the review consulted. Books are arranged 

 in the alphabetical order of the authors' names. The 

 title of each book is followed by full reference to 

 journals where reviews of the book mav be found, 

 and a short quotation from each review, giving, where 

 possible, some idea of the scope and object of the 

 work. The compilers have wisely refrained from 

 expressing any opinion of their own as to the value 

 of each book, although it appears that an attempt 

 in this direction is made upon the index-cards of the 

 library at Pittsburgh from which this review index 

 has been prepared. It will, however, be found that 

 the extracts quoted from reviews give, in most cases, 

 adequate assistance in forming an opinion as to the 

 merits of each work. 



Photo-electric activity seems destined to play an 

 important part in technical photometry. In No. 349 

 of the Scientific Papers of the U.S. Bureau of 

 Standards Mr. K. S. Gibson gives an account of ex- 

 periments on photo-electric spectrophotometry by the 

 null method, using potassium hydride cells now on the 

 market. Such cells give a maximum response, 

 usually near 460/^// ; consequently, the method admir- 

 ably supplements the visual and photographic 

 methods, being best in the blue and violet parts of 

 the spectrum, where they become poor, and becoming 

 poor only after they have become trustworthy. Bv 

 employing the null method, first brought out bv 

 Richtmyer, errors due to want of direct proportionality 

 between photo-electric current and exciting radiant 

 power, and to the current through the cell when not 

 irradiated, are eliminated. Experiments have also 

 NO. 2619, VOL. 104] 



been carried out on diffuse spectral reflection, and ihr 

 method is applicable to the measurement of the rel;i- 

 tive radiant power of two sources and to the measun - 

 ment of fluorescence. In another publication of thi 

 same series (No. 344) Messrs. W. VV. Coblentz and 

 H. Kahler give data as to the change in the electrical 

 resistance of the sulphide of silver and of bismuth 

 when exposed to radiations of wave-lengths extending 

 from o-6/i to 3/1. Galena, cylindrite, pyrites, and 

 jamesonite did not show any noticeable sensitivity. At 

 very low temperatures the intrinsic sensitivity of 

 silver sulphide was greatly increased — a result of in- 

 terest in connection with the fact that some substances 

 exhibit luminescence only at low temperatures. 



Part ii. of a pajjer on the cutting power of lathe- 

 turning tools was read at the Institution of Mechanical 

 Engineers on December ig by Mr. George \V. Burley, 

 of Sheffield University. Part i. was read in 1913 by 

 Prof. W. Ripper, and a number of points raised in 

 the discussion are dealt with in the present paper, 

 which gives an account of the continuation of the series 

 of experiments. .Among the conclusions arrived at is 

 the fact that there is no practical cutting speed below 

 which it is impossible to obtain a satisfactory finished 

 surface on plain-carbon steels by the use of tools of 

 plain-carbon tool-steel, ordinary (non-vanadium) high- 

 speed steel, or superior (vanadium) high-speed steel, but 

 there are upper limits as follows : — For finishing mild 

 steel, 48 ft. to 58 ft. per minute for each,of the three 

 varieties of tool-steel ; for finishing hard steel, 23 ft. 

 to 28 ft., 17 ft. to 21 ft., and 28 ft. to 34 ft. per 

 minute respectively for the three varieties of tool-st(!el 

 mentioned above. The cutting power of a high-speed 

 lathe tool is influenced by both the cross-sectior al 

 area of the shank of the tool and the nose-radius, but 

 the influence of the latter factor predominates. Thus, 

 with a number of different sections of tool-steel, an 

 increase of 100 per cent, in nose-radius produced an 

 average increase of cutting power of 45 per cent. ; 

 whereas an increase of the shank cross-section of the 

 tool of 500 per cent, with a constant nose-radius pro- 

 duced an average increase in the cutting power of 

 only 85 per cent. There is no marked difference in 

 the net amounts of energy required per cubic inch 

 of material removed from mild-steel and hard-steel 

 bars at high and low cutting speeds. 



Messrs. Longmans and Co. expect to publish in 

 January " .\pplied .\ero-Dynamics," L. Bairstow ; 

 "The Design of Screw Propellers, with Special Refer- 

 ence to their .Adaptation for .Aircraft," H. C. Watts; 

 "Telephonic Transmission, Theoretical and .Applied," 

 J. G. Hill; and vol. i. (The Extremities) of "A 

 Manual of Practical Anatomy," Prof. T. Walmsley. 

 Others books, in the press or in preparation, by the 

 same house are: — "An Introduction to the Study of 

 Terra Sigillata, Treated from a Chronological Stand- 

 point," Dr. F. Oswald and T. D. Pryce ; " Structural 

 Steelwork," E. G. Beck; "Tuberculosis and Public 

 Health," Dr. H. H. Thomson; "Food Supplies in 

 Peace and War," Sir R. H. Rew; vols. ii. and iii. of 

 "A Manual of Practical Anatomy," Prof. T. Walms- 

 ley; and, as already announced, "The Life and Work 

 of Sir Jagadis Chandra Bose," Prof. P. Geddes. 



