August 2: 



1919] 



NATURE 



493 



INDUSTRIAL FATIGUE. 



I^HE Industrial Fatigue Research Board, which 

 was recently appointed by the Department of 

 Scientific and Industrial Research and the Medical 

 Research Committee jointly, has quickly got into the 

 sw^ing of its labours. It has just issued two brief 

 reports, and announces other more lengthy reports 

 which are in preparation. In Report No. 2 Mrs. 

 Ethel E. Osborne describes "The Output of Women 

 Workers in Relation to Hours of Work in Shell- 

 making." The women were engaged in the opera- 

 tion of "ripping" or "part-off" on 6-in. shells, and 

 their output was compared when they were on twelve- 

 hour and eight-hour shifts. The output of work 

 achieved during each hour of actual work in the 

 shorter shifts was 65 per cent, greater than in_ the 

 longer shifts, but because of the improvement in time- 

 keeping and the more efficient running of the 

 machinery the production per hour of factory work 

 was 15 per cent, greater. Determinations of hourly 

 output showed that during the last hour of the long 

 shifts there was always a low output, whilst on the 

 short shifts output was maintained throughout. 



In Report No. 3 Col. C. S. Myers, a member of 

 the Board, describes "A Studv of Improved Methods 

 in an Iron Foundry." Hitherto the American 

 methods of time and motion study have gained very 

 little acceptance in this country, and the enterprismg 

 managing director of the iron foundry investigated by 

 Col. Myers is greatly to be congratulated on his 

 initiative in applving the methods practically to the 

 production of small iron castings. Although the hours 

 of work were at the same time reduced from fifty-four 

 to forty-eight per week, the men were able to increase 

 their total output greatlv, and they suffered less 

 fatigue. The men were on piece rates, but they were 

 paid on the novel, but wholly equitable, principle that 

 the greater their oroduction the greater their scale of 

 pav per piece, or* the rate of pav rose automaticallv 

 with increase of total output. In that the overhead 

 charges of a factory are usually almost the same 

 whether the output of a worker be small or great, it 

 is only fair that employers should adopt this system 

 of payment, but it is absolutely exceptional for them 

 to do so. 



MEAN SEA-LEVEL.^ 



THE science of oceanography is slowly coming into 

 its own, and it has advanced greatly in the last 

 twenty years ; but still, of those who think of it at all, 

 many people know verv little what it is. It is looked 

 upon, often enough, as an easy, descriptive science, 

 a small part of a simple, descriptive geography. But 

 if this be true at all, it is a very small part of the 

 truth; for the great problems of oceanography are 

 physical problems, to be approached by mathematical 

 methods, and soon involving us in difficult questions 

 of hydrodynamics, and other difficulties besides. In 

 the elementary task of the exploration of the sea 

 Englishmen have taken a large, perhaps a lion's, 

 share; in one special part of scientific hydrography, 

 the theory of the tides, they have done a great deal, 

 for such "names as Lubbock, Whewell, Airy, Kelvin, 

 and George Darwin come at once to our minds. But 

 in other parts of the subject, and in recent times, we 

 have done less; and the Scandinavian countries 

 especially have done a great deal more. Bjerknes, 

 Witting,' Otto Pettersson, Sandstrom, Fridjof Nansen, 

 Helland-Hansen, Madsen, and De la Cour are only a 

 few names of men who, from Denmark to Finland, 



1 Rolf Witting : " Haf«vtan, Geoidvtan och I,andh5jn)neen utmed 

 Baltiska Hafvet och vid NordfjSn." Fennia 30, .No. 5. (Helsingfors, 

 19«8.) 



NO. 2599, VOL. 103] 



have studied the hydrographical phenomena of the 

 Baltic or the wider problems of hydrography. 



Among its most fundamental problems are those 

 connected with the determination of mean sea-level — if 

 we may so speak of something that has never yet been 

 determined. There is scarcely a physical constant so 

 freely spoken of or so often used ; every elevation in 

 the world is referred to it, but no man knows what 

 it is. Two or three generations ago a few observa- 

 tions of consecutive tides were supposed to be enough 

 to ascertain it — a month was ample ; but we have long 

 known that the "constant" so determined is no con- 

 stant at all, but is subject to complicated fluctuations, 

 some regular and some, at first sight, erratic. This 

 first approximation to "mean sea-level" has a very 

 appreciable annual fluctuation, an "annual tide"; it 

 alters from year to year; at any one locality these 

 changes are apparently irregular, but they are 

 found to tally with one another over large areas of 

 coast; there are important differences of sea-level 

 between one station and another; and there are slow 

 changes of long period which again may be found 

 common to large areas. Among the elementary diffi- 

 culties of the problem is the fact that the annual 

 change of level is much too great for a simple astro- 

 nomical explanation— it is not a "solar tide"; and, 

 that being excluded, we are thrown back on two 

 hypotheses or sets of hypotheses, the one meteoro- 

 logical, the other based in one way or another upon 

 movements of the earth's crust. A great deal has 

 been written on the subject in recent years ; we cannot 

 attempt to reviev/ the whole question, but must be 

 content to give an abstract of an important paper 

 lately published by Prof. Rolf Witting, of Helsingfors, 

 director of the Oceanographical Institute in that 

 University. 



The "level " of the sea, or, more generally speak- 

 ing, the form of the surface of the sea, is a resultant 

 of forces both extrinsic and intrinsic; that is to say 

 (after we have eliminated by a sufficient number of 

 observations the effect of the tides), we have to deal 

 with the densities and currents of the sea itself, and 

 with the winds and the atmospheric pressure acting 

 upon its surface. It is plain that where the sea is less 

 dense its surface will tend to stand at a higher level 

 than where it is more so; this is an intrinsic pheno- 

 menon. As to the extrinsic forces, inasmuch as the 

 winds are determined by the distribution of atmo- 

 spheric pressure, the latter may be employed as our 

 common indicator for both factors— that is to say, for 

 the winds and for their effect upon the sea. ^ 



For the latter, or extrinsic, forces Prof. Witting 

 gives us the following law or laws: — (i) Every baro- 

 metric distribution of anv permanency produces a de- 

 formation of the surface of the sea. (2) The ascending 

 slope so produced is not identical in direction with 

 the barometric gradient, but deviates to its right-hand 

 side, in the northern hemisphere. (3) The amount of 

 slope is greater than that which would correspond with 

 the hydrostatic pressure induced by the barometric 

 distribution. (4) The amount of the deviation, and 

 also the ratio between the amount of slope and the 

 barometric gradient, are (to a first approximation) 

 independent of the gradient, but largely affected by the 

 shape of the basin and by the distribution of densities 

 in its water-lavers. 



From Fig. i we may judge, for a particular date, 

 the relative directions of the barometric gradient and 

 of the sloping surface of the Baltic Sea. 



In a celebrated observation (to which, bv the way, 

 Prof. Witting does not happen to refer) Sit James Ross 

 found that, at a certain' point within the Antarctic 

 Ocean, a change of barometric pressure produced, to 

 all intents and purposes, its precise hydrostatic equiva- 



