September 13, 191 7] 



NATURE 



33 



bridge, contains particulars of many interesting, and 

 some scarce, works in anthropology, archaeology, folk- 

 lore, mythology, botany, geology, mathematics, astro- 

 nomy, and physics. We notice in the astronomical 

 section a set of the AstrophysicaL Journal, and the 

 Nautical Almanac" for 1875-1916. 



OUR ASTRONOMICAL COLUMN. 

 Relativity and Gravitation. — According to the 

 original form of the theory of relativity, an absolute 

 \ elocity v in space cannot be determined by any phys- 

 ical means, all matter as well as electrical and optical 

 fields being contracted, in the terminology of the older 

 physics, in the same ratio {i—v^/c')i. tJsing the same 

 terminology, Einstein's recent gravitational theory re- 

 quires a gravitational field to suffer contraction in this 

 same ratio, so that an absolute velocity v must remain 

 for ever hidden from our knowledge. Einstein has 

 shown that this theory, suitably generalised to cover 

 independently-moving bodies, leads to changes in the 

 I>erihelia and eccentricities of the four inner planets 

 which agree well with those observed. In the Phil. 

 Mag. for August Sir Oliver Lodge suggests an alterna- 

 tive explanation of the changes in Mercury's orbit. In 

 accordance with pre-relativity theory, the mass of Mer- 

 cury, when moving with velocity v, is suppo.sed to be 

 ))io(i — ■y^/c^)~i; of this only the stationary mass m„ is 

 supposed subject to gravitation, while the sun's gravi- 

 tational field is not supposed to suffer distortion as it 

 moves through space. The assumed increase in 

 inertia, uncontrolled by gravitation, is found to lead 

 to a revolution of Mercury's orbit in its own plane, 

 which will agree with that observed if the sun has a 

 velocity of about 68 km. a second towards longitude 

 294°. This velocity would also give an apsidal pro- 

 gression for Mars about equal to that observed, but in 

 the September Phil. Mag. Prof. Eddington has shown 

 that it would give orbital distortions for the earth and 

 Venus enormously greater than those observed. In 

 these papers no allowance is made for the distinction 

 between longitudinal and transverse electromagnetic 

 mass, but it seems impossible that this correction 

 could reconcile theory with observation ; indeed, the 

 discussion Suggests that no theory of the general type 

 suggested by Sir Oliver Lodge can be made to fit all 

 the facts, so that the relativity theory appears to be 

 left in a stronger position than ever. 



Photographs of Nebulae. — A remarkable collection 

 of photographs of nebulae taken with the 60-in. reflector 

 of the Mt. Wilson Observatory has been published by Mr. 

 F. G. Pease {Astrophysical Journal, vol. xlvi., p. 24). 

 The objects selected were in general nebulae of un- 

 known structure, or nebulae which were known to 

 exhibit unusual features. Most of the exposures were 

 made with aperture ratio F/5, but several of the 

 bright planetary nebulae were also photographed with 

 the 80- and loo-ft. focus Cassegrain arrangements of 

 the telescope, in order to give a larger scale. The 

 exposures ranged from ten minutes to seven hours. 

 It is interesting to note that the perfection of the 

 photographs was increased in the case of very long 

 exposures by the use of two guiding stars, which 

 allowed of correction being made for variation in size 

 and for rotation of field produced by refraction and 

 imperfect adjustment of the telescope. In addition to 

 the sixt\'-five nebulae which are fully described, atten- 

 tion is directed to others which appeared incidentally 

 on the plates, and to a number of uncatalogued nebulae 

 and nebulous stars. The photographs show a great 

 amount of intricate detail, and bear witness alike to 

 the excellence of the instrument and the skill of the 

 observer. 



The ioo-in. Reflector' yyT Mount Wilson.— An 

 illustrated description of the great reflector of the 

 Mount Wilson Observatory is given by Mr. Pease in 

 the Scientific American for August ii. As supplement- 

 ing the account already given in the columns of Nature 

 of July 12 (vol. xcix., p. 385), it may be noted that the 

 moving parts of the telescope, which is mounted on 

 the English pattern, weigh 100 tons. The greater part 

 of the weight is taken up by the mercury flotation 

 system, 40 tons at the north pedestal and 60 tons at 

 the south pedestal. The driving clock is regulated by 

 an isochronous governor of the conical pendulum type, 

 and the weight is wound up automatically at intervals 

 of twelve mmutes without interference with the driv- 

 ing. The clock itself stands 6 ft. high and occupies a 

 floor space of 5^ ft. by 4 ft. The actual diameter of 

 the mirror is 101-2 in., and its focal length 5075 in., 

 giving an aperture ratio of 505. Elaborate arrange- 

 ments have been made to maintain the mirror at 

 constant temperature by water circulation. Manipula- 

 tion of the dome and telescope involves the use of 

 forty motors of 1/20 to 7^ horse-power, with an aggre- 

 gate of 50 horse-power and more than thirteen miles of 

 wiring. It is estimated that about 300 million stars 

 will be within range of the new instrument. 



INDUSTRIAL FATIGUED 



T TNDER the above title Prof. Spooner has collected 

 ^ articles written by him in 1916 for publication in 

 Co-partnership. The pamphlet is a useful con- 

 tribution to the discussion of reconstruction, which 

 already is receiving anxious attention from many who 

 realise its extreme importance and its extreme diffi- 

 culty. 



Evidently in so small a space but few details can 

 be given, but the author has touched upon many points 

 which show how wide is the problem and how great 

 are the difficulties which surround it. Perhaps the 

 main impression left upon the mind after a perusal 

 of these fifty-nine pages is one of the immense amount 

 of scientific investigation which remains to be done 

 before industrial processes — to say nothing of industrial 

 management — can be placed on a thoroughly satis- 

 factory footing. It is only quite recently, and largely 

 on account of present conditions, that the general 

 public and directors of industry have begun to realise 

 that science after all is merely crystallised and sys- 

 tematised knowledge, and that to attempt to conduct 

 industrial processes without it is to dispense with one 

 of the greatest aids to success. Now, however, the 

 leaven is spreading. Many firms operating processes 

 which depend on scientific principles have their own 

 scientific staff working in admirably equipped labora- 

 tories, and so far as their own processes are concerned 

 little more is needed, though it would undoubtedly con- 

 tribute to the general advance if the results of the 

 investigations carried out could be made available for 

 all to profit by. But apart from these questions there 

 are larger problems which affect all industries, and 

 which can only be dealt with effectively by some 

 central authority. Such, for instance, is the question 

 of the number of hours' work per week which will 

 enable an operative to produce the largest output 

 without injurious fatigue. Evidently no general answer 

 can be given to such a question. The answer must 

 vary with conditions, and all conditions must be 

 studied in order that their influence in producing 

 fatigue may be determined. But certain fundamental 

 facts may be established, and perhaps the most im- 



1 " Industrial Fatigue in its Relation to Maximum Output." By Henry I. 

 .Spooner, C.K. Forewords by Sir Robert Hadfield, F.R.S., and Mr. J. R. 

 Clynes, M.P. (Co-partnership Publishers, Ltd., 6 Bloomsbury Square, 

 W.C.i.) PriceW.net. 



NO. 2498, VOL. 100] 



