408 



NATURE 



[January 23, 1919 



publii .11 large; the Patenl Law requires to be so 

 framed that each of these interests -.hall be pro- 

 vided with suitable safeguards. Therefore, whilst 

 i iv desirable thai the ambil of a patenl should 

 be widened and its validity after introduction made 



less open to impeachment, there is no good reason 



For extending the present statutory term ol a 

 pateni, which is founded on the old practice ol 

 apprenticeship; moreover, it must always be borne 

 m mind that during the period of a strong mono- 

 poly all incentive to improvement is removed, a 

 situation being , reated which is as much to the 

 detriment oi the inventor and of the capitalist as 

 of the individual consumer, and of the State also. 



NATURAL AND ARTIFICIAL CAMOU- 

 FLAGE. 

 IN an interesting essay on "Camouflage 

 (Scientific Monthly, December, rgi8, pp. 



a.!si .))) Mr. Abbott il. Thayer illustrates his well- 

 known conclusions in regard to the cryptic colora- 

 tion of animals that hunt or are hunted. In their 

 "superhuman perfection" the concealing coats ol 

 wild animals have become the models for the 

 camouflage corps of armies. The patterns which 

 animals exhibit "always inevitably tend to con- 

 ceal," and that in direct ratio to their strength — 

 i.e. the degree of difference among the component 

 notes. " Monochrome, no matter how grey, 

 reveals its wearer against all backgrounds what- 

 soever (and most of all if these are monochrome) 

 except a background which is an absolute repeti- 

 tion of itself." What is practically universal is 

 background-imitation, the deeeptiveness of which 

 is overwhelming. Mr. Thayer illustrates this by 

 interesting views of brook-scenes and wood- 

 scenes photographed through a stencil of bird or 

 beast. The creature has the garment of invisi- 

 bility because its "costume is pure scenery. " " All 

 the patterns and brilliant colours on the animal 

 kingdom, instead of making their wearers con- 

 spicuous, are, on the contrary, pure concealing 

 coloration, being the actual colour notes of the 

 scene in which the wearer lives, so that he really 

 is Nature's utmost picture of his background." 

 Even the scarlet bodice of the scarlet tanager, 

 by being a perfectly unbird-shaped scarlet patch 

 amidst the forest foliage, is effective because it 

 corresponds with the sprinkling of single scarlet 

 leaves throughout the trees. 



[wo points mUSl be borne in mind : (t) that the 

 costume of a creature that does not change much 

 throughout its life will correspond with "an average 

 and expectable type of scene"; and (2) that what 

 catches our eye may be quite elusive to the animal . 

 the sight of which was to be deceived, for a skunk 

 that may seem to man conspicuous has been 

 < "loured "for concealment from the small 

 creatures on which he feeds, and above which 

 he looms against tin sky." 



It may be questioned, however, whether we 

 know very much about the vision of the small 

 creatures referred to. And when to the con- 

 clusion : "This resultant background-imitation is 

 NO. 2569, VOL. I02] 



practically the universal accomplishment of 



animals' patterns," Mr. Thayer adds: "1 have 

 bee 11 left alone in the world to point this out," 

 many readers will naturally wonder where Alfred 

 Russel Wallace, lor instance, comes in! This 

 is a historical question, however, and the aim of 

 Mr. I haver's essay is largely practical namely, 

 the statement of a law ol camouflage. "Man has 

 only to i ut out a Stencil ol the soldier, ship, 



Oannoh, or whatever figure he wishes t in i al, 



and look through this stencil from the viewpoint 

 unci, i consideration, to learn just what 

 Costume from that viewpoint would most tend to 

 conceal this figure. " 



That this is not the whole doctrine of camou- 

 flage is suggested by the recent exhibition of 

 "dazzled " ships or models ol ships at Burlington 

 House, where Lieut. -Commander Wilkinson's 

 devices were admirably illustrated. The curious 

 patterns of designs which have been painted on 

 so many merchantmen and patrol-boats were 

 thought out by Commander Wilkinson — like Mr. 

 Thayer, an artist — not to make the ship incon- 

 spicuous, but to break up its form in such a way 

 as to make it difficult for an attacking C-boat to 

 estimate the course. A vessel at rest near the 

 Cliffs of a fjord or against the background of a 

 Wooded island can be camouflaged in various 

 Ways so as to become inconspicuous, but the 

 "dazzled" ships expressed another idea, and 

 elaborate trials have shown that even old, experi- 

 enced seamen are so deceived by the strange de- 

 signs that their estimate of the direction in which 

 the ship's bows are actually pointing is usually 

 wrong, and sometimes ludicrously wide of the 

 mark'. It is probable that some bird-designs — e.g. 

 white tail-feathers— may have the same effect of 

 breaking up the form of the' body, thus making it 

 more difficult for hawks to take- a sure aim. 



DR. II. E. J. 1)1' HOIS. 



DR. DU BOIS, whose deatli occurred at 

 Utrecht on October 21, has left behind him 

 a record of valuable work in magnetism, in optics, 

 and in radiation. It was especially the connection 

 between magnetic phenomena and the polarisation 

 of light which led him into optical fields of re- 

 search. Thus his earliest paper published in the 

 Annalen der Physik und ('hemic in 1X87 deals 

 with magnetic circular polarisation in cobalt and 

 nickel. In 1889 Dr. Du Bois made his first ap- 

 pearance at the British Association, which met that 

 year in Newcastle, and gave an account of his 

 experiments on the Kerr effect in magneto-optics, 

 showing how it could be used in the measure- 

 ment ol strong magnetic fields. The complete 

 papet was published in t8go in the Inn. J. Phys. 

 u. (hemic and in the Philosophical Magazine 

 (vol. xxix., p. 253). This paper was noteworthy 

 both for the novelty of the method used and for 

 the admirable manner in which the method was 

 worked out. The fundamental idea was to 

 measure the magnetisation at the surface of mag- 

 netised spheroids of iron, nickel, and cobalt by 



