492 



NATURE 



[December 30, 19 15 



tive equivalents of different agents, as compared with 

 1000 Board of Trade units of electrical energy. 



Table of Efficienxies for Continuous Heating. 

 The rates given are those current in London previous 

 to the war and at present : — 



Approximate equivalents. 



Ull I 



Rates 



■per 



Gross 

 cost 



Relative 

 cost 



I.OCO 



Electric Radiator. 



/•Board of Trade^ 

 Units of Elec- 

 trical energy 

 utilised in best 

 radiant stove 

 of 69% radiant 

 efficiency dis- 

 posed in the 

 best manner . 



Open Fire. 



1-38 tons of/ 

 best house 

 coal, 14,000-^ 

 B.T.U. per 

 lb. ... 



0-520 ton best 

 house coal, 



14,000 

 B.T.U. peri 

 lb. ... 



0*235 'o" ^'^st , 

 anthracite, 



14,500 \ 

 B.T.U. per 

 lb I 



Burnt in bad | 

 grate unsuit- 

 ably disposed . 



Burnt in best 

 open modern 

 grate sunk in 

 wall ... 



26/- 



35/- 



26/- 



35/- 



Closed Anthracite Stove. 

 Burnt in best] 



modern slow I 



combustion, !- 45 



closed anthra- 1 



cite stove ... I 



40/- 

 50/- 



i-s 



2-42 



0-675 

 0-91 



0-47 

 0-59 



Gas Stove. 



18,300 cub. ft. I'Burnt in medium"! 

 gas. at 520 I old - fashioned (_ 

 B.T.U. perl gas fire (not! 

 cub. ft. ...{_ woi'st type) ...J 



10,700 cub. ft. I'Burnt in best 

 gas, 520J modern ven- 

 B.T. U.. perl tilating gas 

 cub. ft. .. \, stove 



36 



62 



Water Radiators. 



'Burnt ill best pro- 

 vided modern 

 water boiler 

 with well- 

 clothed circu- 

 lation to radia- 

 tors or pipes . 

 In usual smain 

 0-306 ton of I house hot I 

 coke, 12,500! water instal- 1 

 lation asj" 

 generally in- 1 

 stalled J 



o-jgS. ton^ of 

 coke, 12,500 

 B.T.U. per 

 lb 



00! 

 B.T.U. perl 



'^ I 



62 



Oil Stove. 



19-5 gallons rComple t e 1 y^ 

 petroleum! burnt in any 

 0-87 gravity, | kind of stove I 

 1 disci 

 I produ 

 I air of 



20, 240 

 B.T.U. per 

 lb. , 



harging 



nets into 



room ... 



20/- 

 30/- 



20/- 

 30/- 



8^. 



10^. 



0-198 

 0-297 



0-306 

 0-4S9 



0-650 

 0-810 



100 

 200 



335 

 400 



10-8 

 14-6 



7-54 

 9-42 



36-6 

 44 



21-3 

 25-6 



3-17 

 475 



4'9 

 7-36 



10-4 

 13-0 



Arthur H. Barker. 



THE PHYSIOLOGY OF INDUSTRIAL 

 FATIGUE.^ 



n'^HE gradual recognition of the prevalence among 

 ^ industrial workers of severe physical or mental 

 fatigue has led during the last few years to a closer 

 study of its harmful effects and to various suggestions 

 as to its prevention. Although moderate fatigue is a 

 healthy and natural event, there is little doubt that 

 unduly prolonged hours of work, particularly if the 

 work is carried on under unfavourable hygienic con- 

 ditions, may lead to such a degree of fatigue that the 

 efficiency and health of the worker are seriously im- 

 paired. The decline in efficiency manifests itself not 

 only in a smaller output of work, but also in many 

 occupations by an increased liability to accidents. 



The prevention of extreme fatigue is, therefore, a 

 matter of great importance, both to the employer and 

 to the worker; but hitherto one of the most serious 

 difficulties in the consideration of the problem has been 

 the lack of any simple and certain test for the presence 

 of fatigue. The question of finding a suitable index 

 of fatigue has recently been taken up by Prof. Stanley 

 Kent, and the preliminary results of his investigation 

 are recorded in a report on industrial fatigue, which 

 has been issued by the Home Office. Prof. Kent 

 examined the influence of fatigue upon certain physio- 

 logical phenomena, namely, the arterial blood-pressure, 

 the reaction time in response to a simple stimulus, the 

 acuity of hearing and of vision. The acuity of hearing 

 was determined by noting the distance from the ear 

 at which the ticking of a watch could be heard, and 

 the acuity of vision was ascertained by noting the 

 distance at which certain letters (test types) could be 

 recognised. 



The main experiments were carried out on three 

 groups of workers — one group of six colliers, one group 

 of six workmen in a chemical works, and one of six 

 workers in the printing trade. The tests were applied 

 twice daily, once before and once after the day's work, 

 over a period of a week or more. 



The experiments on the arterial blood-pressure and 

 the reaction time yielded irregular and discordant re- 

 sults, but it was found that there was a striking 

 diminution in the acuity of both vision and hearing at 

 the end of the day's work, and that in many cases 

 there was a progressive decline during the course of 

 the week. The latter effect might be regarded as 

 evidence of cumulative fatigue towards the end of the 

 week. The decline in visual or auditory acuity was 

 observed in all three groups of workers ; in some mem- 

 bers of each group the diminution amounted to 50 per 

 cent, or more, whereas in others the change was so 

 slight as probably to fall within the limits of normal 

 daily variation apart from fatigue. The large varia- 

 tions in visual or auditory acuity in the same person 

 on successive mornings, or on successive Monday 

 mornings, when the subject was presumably not 

 fatigued, are a prominent feature in Prof. Kent's re- 

 sults. These variations rather suggest that the sub- 

 jective factor (as distinct from fatigue) is an important 

 element in the test ; and the fact that the test is purely 

 "subjective," and that there is no means of checking 

 the worker's statement as to the distance at which 

 he hears a watch or sees a standard letter, is a distinct 

 drawback to these tests. 



Prof. Kent's observations also make it clear that, 

 in some individuals, a day's work or a week's work 

 leads to impairment of hearing but not of vision, or, 

 on the contrary, to impairment of vision but not of 

 hearing. This was noticed in each group of workers. 

 It rnight be expected that, if the decline in visual or 

 auditory acuity is a manifestation of general fatigue, 



1 Report on an Investigation 'of Industrial Fatigue by Physiological 

 Methods. By Prof. A. F. S. Kent. (Home Office.) 



NO. 2409, VOL. 



