July 24, 1919] 



NATURE 



405 



Of the seventy-five, some said nothing rbout annual 

 increment, a few gave the initial salary only, several 

 gave both initial and maximum salaries, and some 

 sufficient data to find the true average value of the 

 salary over a number of years. This information has 

 been used to deduce reasonable estimates of the 

 prospects of advancement in other cases where the 

 full data were wanting. 



The posts were classified into three divisions, which 

 comprised, roughly, (.\) professorships, (B) lecture- 

 ships, and (C) demonstratorships, or the equivalent 

 of these, though of necessity a certain amount of 

 <liscretion was used in the process. The average of 

 the mean (not the minimum) salary in each class was 

 then found, with the following result : — 



Average of 

 Class Number of vacancieti mean salary 



A ... 16 ... 620 



B ... 22 ... 385 



C ... 37 ... 234 



The posts of the first class were nearly all at fixed 

 salaries; those of the second started at, roughly, 

 320/., rising to 450/., per annum; those of the third 

 went from an initial salary of about 200Z. to 270/. 

 These .salaries probably give a fair idea of the value 

 placed by governing bodies on the trained brain 

 at the present day. They are undoubtedly higher than 

 would have been the case in pre-war conditions, at 

 least in the lower and middle of the two classes; but 

 if the best brain-power of the nation is to receive 

 full encouragement—and if labtiur difticulties are to 

 disappear, production increase, and British civilisation 

 advance, this can come only from full encouragement 

 -these salaries are still far from adequate. Monev 

 has to-day little, if any, more than 45 per cent, of its 

 purchasing power previous to the viar. Salaries of 

 zvtol. and 600/. to-day bring their possessors no greater 

 -hares of economic goods than goi. and 270Z. in 1914. 

 It is beginning to be recognised — it is already recog- 

 nised in the United States— that the elevation of the 

 ^'eneral level of prices is now more or less permanent, 

 md that a return to a lower level, at least in this 

 -generation, is improbable, even if it should be desir- 

 able. The cla.ss of manual labourers has had its 

 wages increased almost, if not quite, in proportion to 

 the rise in prices. The mercantile community, work- 

 ing as it does on percentage margins, has made 

 ordinary profits commensurate with that rise, and, in 

 addition, has obtained unearned profits resulting from 

 the rise itself. The class of fixed salary earners, 

 which comprises the brain-workers of the nation, the 

 professional class, has borne the brunt of the rising 

 prices without anything like an adjustment of salarv 

 corresponding with the rise. It is the hardest hit 

 of all by the war, and yet this class, perhaps more 

 than any other, has contributed to winning the war. 

 Hitherto patriotism has kept it silent. Now, how- 

 ever, the time has come when the scale of the pro- 

 fessional man's salary must be revised. Incomes such 

 IS those found above do not admit of the upbringing 

 ind education of a family as befits its inherited 

 liiility; of the expenses inevitable if a man is to keep 

 ibreast of his profession; and of saving and insurance 

 igainst sickness, age, and death. 



"In war-time," writes the Economist of Julv 12, 

 in a "business note" on British and German science, 

 "we make full use of our men of science. If we did 

 -o in peace they might be as useful for production 

 IS they have been for destruction." The first step 

 i< to see that they get what, for them, is a living 

 -alary, else there will be no men of science to use. 

 1 he second step is to see that their teachers get 

 adequate remuneration, else there will be no training 

 to make men of science of them. C. 



NO. 2595, VOL. 103] 



MODERN SINGLE-OBSERVER RANGE- 

 FINDERS. 

 nPHlRTY years ago the War Office asked for 

 -^ a rangefinder for field service that would 

 measure ranges to within 4 per cent, at 1000 yards 

 —that is, 40 yards at 1000 yards, or 160 yards at 

 2000 yards. A single-observer rangefinder of 

 30 in. base was designed to fulfil these require- 

 ments. In 1892 a naval rangefinder was required 

 that would work within an error of 3 per cent, at 

 3000 yards, which is equivalent to i per cent, at 

 1000 yards. This demand was met by a range- 

 finder of 4 ft. 6 in, base. Whereas in 1895 ^^^ 

 effective range of naval gunnery was between 2000 

 and 3000 yards, the effective range in 1904 was 

 6000 yards. For this service a rangefinder of 

 9 ft. base was introduced. 



At the Battle of Jutland in 1916, firing com- 

 menced at a range of more than 20,000 yards, and 

 although the makers had already constructed 

 rangefinders of 15 ft. to 35 ft. base, the majority of 

 the Service rangefinders were still of 9 ft. base, the 

 Fifth Battle Squadron alone having been equipped 

 with 15 ft. base rangefinders capable of measuring 

 a range of 20,000 yards to within 170 yards, an 

 error equivalent to 18 in. at 1000 yards. The 

 30 ft. base rangefinders exhibited by Messrs. Barr 

 and Stroud, Ltd., at their stand at the British 

 Scientific Products Exhibition are designed to 

 work within half this error (Fig. i). • 



Thus in the development of single-observer 

 rangefinders during the past thirty years, the un- 

 certainty of observation has been reduced from 40 

 yards at 1000 yards to the equivalent of 9 in. 

 at 1000 yards ; that is, the accuracy has been in- 

 creased 160-fold. 



This increase of accuracy has been obtained by 

 increasing the base length about 12-fold and the 

 magnification about 3-fold, thus accounting for a 

 36-fold increase. The remainder of the increase 

 has been attained by refinements in the design and 

 construction of the optical and mechanical ele- 

 ments based upon the results of research work 

 conducted continuously during many years by a 

 large staff of scientifically trained observers. 



The accuracy of observation when using a co- 

 incidence rangefinder is ultimately dependent 

 upon the accuracy with which the eye can detect 

 a want of alignment between the partial images 

 of the object in the field of view, and this largely 

 depends upon the manner in which the images are 

 presented for observation, .^s a result of much 

 experience and many experiments on the align- 

 ment of images as presented in the Barr and 

 Stroud rangefinders, it would appear that, under 

 ordinary good conditions of observation, a want of 

 alignment between the images can be detected 

 when they subtend at the eye an angle of about 

 12 sees., i.e. 00000582 in circular measure, 

 although frequently a much smaller angle can be 

 resolved. 



If B is the base of the rangefinder, M the 

 magnifying power, and R the range, then 



SR = 00000582 R7MB. 



