November 7, 1901J 



NA TURE 



Bunsen tube will, in this case, burn with the aid of external 

 heat; but not without sjme such assistance, because the heat 

 of combustion is so much absorbed by the diluting gases that 

 the temperature of ignition would not otherwise be maintained. 



The experiment reminds one of the burning of ammonia, and 

 of a coal-gas flame rendered non-luminous by the admission of 

 steam. 



A consideration of Prof. Smithells' method of cone separation 

 by a glasi rod {vide Nature, November 1S92) might lead to 

 the suspicion that the obstruction of the rod played some part in 

 the phenomenon, but the above explanation is supported by the 

 fact that the copper wire which, when cold, extinguishes a 

 candle flame, does not, when warm, do so. 



Herbert Kini;. 



The School, Wolverhampton, November 2. 



The Colours of Guillemots' Eggs. 



I AM glad to see that my friend Ciptain Barrett-Hamilton 

 has written on the above subject, though it seems inconceivable 

 to him that " the beautiful varieties of colouring must help each 

 bird to distinguish her egu from others lying near until they all 

 become stained and soiled." The quotation is from " The Birds 

 of Ireland " (p. 364), in which I put forward, as an opinion, the 

 conclusion that I have been led to after many a day spent in 

 climbing among breeding guillemots. 



Discussion of such opinions is to be welcomed, but they must 

 be tested by close observation of the birds and their ways ; and 

 the guillemot finding its own egg among many is not the same 

 thing as an animal finding its young, which has voice, smell, 

 movement and expression, nor has the guillemot a nest to find. 



It is asked, " Why should each guillemot be provided with a 

 conspicuous private egg-pattern when other sea-birds, her 

 neighbours, have to find their homes without such aid ? " 



Well, let anyone look down on a guillemot-ledge the last 

 week in May, before the birds have begun to sit close, and he 

 will be struck by the fact that each is provided with a conspicuous 

 egg-pattern, the green eggs contrasting with the white ones and 

 those heavily blotched with the streaked ones ; and this is most 

 obvious, even at some distance. I know no other eggs that 

 show such vivid contrasts. 



Does this contrast supply any want that the guillemot may 

 have above other birds to enable it to find its egg ? Her neigh- 

 bours, my friend remarks, find their homes without such aid. 

 But then each has her "home." The gulls and cormorants 

 have their nests. Each puffin has its burrow. The razorbills lay 

 much more in separate nooks than guillemots, but still they 

 approach nearest to them both in the nature of their breeding 

 places and in the varieties of egg-colouring. But guillemots lay 

 and sit in packs, often touching one another, on open surfaces 

 of rock (see the plate, " Birds of Ireland," facing p. 362). At 

 first the eggs are often left uncovered and other guillemots 

 alight, lay beside them, and ihey roll more or less. Must not 

 the special colouring greatly enable the parent bird to find her 

 egg while this is going on ? Why should we deny her intelli- 

 gence in a matter that concerns her, even though other birds are 

 satisfied if they know the way to their nests and do not seem to 

 distinguish whether the eggs in them are their own or not. 

 Thus the cuckoo's egg is unquestioningly accepted by the foster- 

 mother. 



It is objected that my suggestion about the colour helping 

 guillemots to distinguish their eggs is disproved by the subse- 

 quent admission that ihey all become stained and soiled as 

 incubation advances; but at that si age each bird clings to her 

 treasure and never leaves it, unless her mate relieves her (a point 

 which needs proof). 



The colouring of the eggs of this species is not protective, for 

 it makes them gaudy. It is peculiar, and why should it not be 

 useful during laying-time considering the very peculiar conditions 

 under which guillemots breed ? They sometimes come down 

 with a thump among others which are hatching, they sometimes 

 fight, they are awkward on their feet ; eggs are not only moved, 

 but many are thrown down, broken or lost in pools. 



I wish some ornithologist would contrast fro n observation 

 the guillemots' colonies on surfaces of rock with those of other 

 birds that breed in packs without nests. Penguins appear to 

 lay on earth and leave lanes between the nesting-places on 

 which the birds travel on foot. That being so, tlieir eggs 

 tvou'd not be in such danger of being rolled about. 



Cippagh, CO. Waterford. R. J. Ussher. 



NO. 1 67 I, VOL. 65] 



THE TERCENTENARY OF TYCHO 

 BRA HE'S DEATH.' 



ON October 24, 300 years had elapsed since Tycho 

 Brahe died at Prague, expressing in his last 

 moments the hope that he might not appear to have 

 lived in vain. When saying this he doubtless did not 

 fear that the work he had accomplished might not turn 

 out to be of permanent value, but merely regretted that 

 the great goal he had looked forward to from his early 

 youth, the complete reformation of astronomy, had not 

 yet been fully reached. Could he have foreseen how 

 brilliantly Kepler, who stood at his deathbed, was to 

 complete the work, Tycho would have had no fear as to 

 the lasting nature of his reputation. 



It is difficult nowadays to realise that only a little more 

 than 300 years ago it was not a self-evident proposition that 

 the science of astronomy could only be firmly established 

 by observing the heavens systematically year after year, 

 and not merely by taking an odd observation now and 

 then. And yet this does not appear to have occurred 

 to anybody before Tycho, as even Copernicus records 

 very few observations taken during his long life, so that 

 the values of most astronomical quantities had still to be 

 borrowed from Ptolemy. But in .August 1563 the young 

 Danish noble, then a student at the University of Leipzig, 

 only si.xteen years of age, commenced the series of obser- 

 vationswhich he carried on, with few'interruptions, till the 

 end of his life, thirty-eight years later. The instruments 

 he used at first were crude enough, but already at that 

 time the future reformer of practical astronomy was 

 aware that a very inferior instrument may produce good 

 work if all sources of possible errors are investigated 

 and corresponding corrections are applied to the results 

 of the observations. It is also worth noticing that the 

 planets almost from the beginning claimed his undivided 

 attention, so that the youthful observer had perceived 

 that the existing planetary tables could only be improved 

 if the computed places of the planets were systematic- 

 ally compared with observed places and the errors of 

 the tables thus brought to light. Thanks to the great 

 liberality of King Frederic II. of Denmark, Tycho was 

 afterwards able for more than twenty years, with a 

 multitude of instruments of improved construction and 

 assisted by a number of pupils, to follow the motions 

 of the sun, moon and planets, while he at the same time, 

 by his observations of a thousand fixed stars, gave to 

 the world a catalogue of accurate positions of these 

 bodies which took the place of the old catalogue of 

 Ptolemy and held its own for more than a hundred 

 years, until the use of telescopes and clocks of precision 

 enabled Flamsteed to produce much better star places. 



That Kepler made use of Tycho Brahe's observations 

 to find the laws which govern the planetary motions and 

 thereby to free the Copernican system from the e.xcentric 

 circles and epicycles which it had taken over from the 

 Ptolemean system is too well known to require repeti- 

 tion here. But Tycho did a great deal more than merely 

 amassing materials for his successor. Not only was he 

 the first observer who did not assume his instruments 

 to be faultless but who studied their errors of construc- 

 tion, but he was also the first to investigate refraction 

 and to attempt to correct his observations for it, and 

 he succeeded in improving his instruments so much 

 that it is ditficult to see how a much greater accuracy 

 could have been attained by succeeding generations, if 

 the telescope had not been invented a few years after 

 his death and if the application of the pendulum to 

 clocks had not simplified many methods of observing. And 

 Tycho was able to deduce many important results from 

 his own observations. By showing that the comets 



xiv Octobris 



1 "Tychonis Erahe Dani d 

 operum primitias De Nova Slell, 

 iMjcietasScicnliarum Danica. H; 

 Pp. 16 -h 54 ff. -i- pp. 30 ; 2 plate- 



MDCI defuncti 

 nuo ttliHit Regia 

 .• Octobris A. D. M DCCCCl." 



