April 25, 1918] 



^^■vancement of science in the forefront of its political 

 ■■^jgramme. What the Labour Party stands for in all 

 fi fields of life is, essentially, democratic co-operation ; 

 and co-operation involves a common purpose which 

 can be agreed to ; a common plan which can be ex- 

 plained and discussed, and such a measure of success 

 in the adaptation of means to ends as will ensure a 

 immon satisfaction. An autocratic sultan may govern 

 : I bout science if his whim is law. A plutocratic 

 irty may choose to ignore science, if it is heedless 

 lether its pretended solutions of social problems that 

 ly win political triumphs ultimately succeed or fail. 

 ■lit no Labour Party can hope to maintain its posi- 

 ti unless its proposals are, in fact, the outcome of 

 1 • best political science of its time; or to fulfil its 

 impose unless that science is continually wresting new 

 fields from human ignorance. Hence, although the 

 r.uipose of the Labour Party must, l)v the law of its 

 •ng, remain for all time unchanged, its policy and 

 - programme will, we hope, undergo a perpetual 

 vflapment, as knowledge grows, and as new phases 

 the social problem present themselves, in a continu- 

 iv finer adjustment of our measures to our ends. 

 1 1 law is the mother of freedom, science, to the Labour 

 I'arty, must be "the parent of law." 



In this spirit all students of science may unite. 

 l"h rough it, and not otherv^rise. may the decay of 

 civilisation be arrested, and the fair fruits of ages of 

 tort brought to maturity. T. D. A. Cockerrll. 



Uoulder, Colorado, March, 1918. 



NATURE 



45 



The Motion of the Perihelion of Mercury. 



The type of resistance suggested by Sir Oliver 

 Lodge (Nature, April 18, p. 125) is very difficult 

 'o visualise. The motion of a planet consists prac- 

 lically of a siteady motion in a circle, with a super- 

 imposed free vibration, the amplitude of which is pro- 

 portional to the eccentricity, and the phase of which 

 it'pends on the longitude of the perihelion. The 

 h\pothesis that the perihelion can be made to move 

 I bout alteration in the eccentricity is equivalent to 

 -liming that a free vibration can persist in a resist- 

 ; medium without change of amplitude. It is true 

 it the absolute resistance would be expected to be 

 ater at perihelion than at aphelion, on account of 

 • difference in density at the two points, but tihis 

 Urence contains the eccentricity as a factor, and it 

 lor this reason that the rate of decrease of the eccen- 

 .icity and the motion of the perihelion would be of 

 I hi' same order of magnitude. 



rhe limitation of the resistance to a force parallel 



to the minor axis would mean that the departure of 



the orbit from circularity determines a very small 



[jart of the resistance, most of this being due to a 



general motion of the medium in that direction with 



I \(!locity far exceeding the parabolic velocity. Even 



hout the difficulties introduced by the high density 



Liired, such a velocity could not be accepted. 



< )ne effect of a difference between longitudinal and 



iisverse electromagnetic masses was shown by Mr. 



W. Walker, in the April Philosophical Magazine, 



r ) 1)6 a change in the plane of a planet's orbit. The 



nature of this change can be found without much 



lifticulty to be a rotation of the plane about the pro- 



tion on itself of the sun's motion in space, the 



id of rotation being proportional to the product 



>)i the components of the sun's motion in and per- 



p^-ndicular to the plane. The rotation being about an 



axis in the plane of the orbit, the effect on the nodes 



should he much less than that on the inclinations, 



whereas the contrary is the case. Thus it seems that 



the motion of the node of Venus cannot be accounted 



for in this wav, and etther one of the two component 



NO. 2530, VOL. lOl] 



velocities must be very small or the effect of absolute 

 motion on electromagnetic mass must be in some way 

 compensated in the law of gravitatwn itself. The 

 absence of the variations in the eccentricities that 

 would be expected to be produced by a mci:ion of the 

 sun through space also suggests that there is such a 

 compensation. Harold Jeffreys. 



A Plea for the Naturalist. 



The naturalist is not so black as he is painted. 

 Conditions of modern technological inquiry are against 

 him ; the splitting of species into geographical and local 

 races, distinguished by the finest touches of colour or 

 the minutest of structures, has put the detailed identi- 

 fication of many of our native creatures beyond his 

 compass. 



But there is still a wide field for the naturalist, the 

 closer observation of the habits of our native creatures. 

 It is to be regretted, therefore, that in this his proper 

 field his work should be slighted and minimised by 

 the worker who prides himself, and rightly, on his 

 technical equipment for specialised work. In a recent 

 issue of Nature (March 21) a writer groupcxi 

 naturalists with "landowners, sportsmen, farmers, 

 rat-catchers," as well as a large class of bird-lovers, 

 as being of the people whose personal opinion " is really 

 of very little moment," in a matter which, after all, 

 is mainly one of observation — ^an inquiry into the 

 economic significance of the feeding habits of birds. 



Why the fact that a man possesses -or farms a few 

 acr'es should invalidate his natural history observa- 

 tions is not easily understood. And, after all, are the 

 opinions of the naturalist really so much at fault? 

 Many times during the last few years we have been 

 told in effect that years of careful work by an experi-_ 

 enced investigator, supplemented by the researches of' 

 many others, had at last made it "possible to state 

 definitely that, at the' present time there is ample 

 evidence of a far-reaching kind to prove that no 

 quarter should be shown to the wood-pigeon," that 

 the rook " is far too plentiful at the present time, 

 that it prefers a grain diet, and that it is injurious," 

 that " the starling has increased in numbers enor- 

 mously," and that "the bullfinch and blackbird in 

 fruit-growing districts are most destructive." 



But the naturalist knew and had recorded these 

 things; pigeon-shoots are not affairs of yesterday; and 

 already in the early part of the fifteenth century the 

 Scottish Parliament had passed a law for the destruc- 

 tion of rooks precisely on account of their " gret skaithe 

 apone cornis." On the whole, the naturalists and 

 farmers were right, and minute researches have con- 

 firmed thejir general opinions. 



On the whole, too, the results of the minute re- 

 searches are less definite than would at first sight 

 appear, for, apart from the difficulty of contrasting 

 vegetable with animal food as it is represented in the 

 food canal of a bird some time dead, there is the 

 danger of reaching conclusions from unconsciously 

 selected spHJcimens. The gull on the turnip-field is 

 likely to be shot and sent for examination, that on the 

 offal of the fishing village is likely to be left unharmed, 

 and the percentage of injury caused by gulls rises ac- 

 cordingly. No one would dream of deprecating such 

 inquiries as have been carried on. They are necessary 

 and of the greatest value, and in the hands of an 

 organised group of observant workers of wide sym- 

 pathies they will yield a large proportion of truth. 

 But they are not infallible. 



The contributions of both naturalist and laboratory 

 expert are necessary to the fullness of this knowledge, 

 but one without the other leans on a broken reed. 

 April IT. James Ritchie. 



