March 24, 1892] 



NATURE 



485 



I accordingly had two sleeves prepared, one of turned and 

 polished iron, the other left with a thick coating of oxide. 

 Two sets of experiments, in each of which six observers took 

 part, were made. In each set of experiments three observations 

 were made with the polished, and three with the oxidized sleeve. 

 In each case the observers were in the dark room for some 

 minutes before the experiments began. 



In the first set of experiments the observers gave their opinion, 

 at the conclusion of the experiments, as a body, that the first 

 appearance of colour was a greyish-white ; as the sleeve became 

 hotter the colour was yellow, and gradually changed into orange. 

 There was little or no difference between the observers as to 

 the instant of visibility ; it was generally over a minute before 

 the sleeve became visible, the light generally showing first on 

 the generating line of the cylinder between the eye and the axis. 



There was no difierence in colour between the bright and the 

 oxidized sleeves. 



In the second set of experiments, the observers had no 

 communication with one another, had no idea what colour they 

 were expected to see, and their impressions were written 

 down separately and independently. Their impressions were 

 as follow, the observers being designated by a, )3, &c. '.— 



(o) First colour visible, grey white, second colour white with a 

 little mauve, third pale rose, fourth orange. The above was the 

 first experiment (polished metal). The other experiments showed 

 same colour, but no mauve seen. In the last experiment (a 

 very low heat) the colour never passed beyond a pale yellow. 



(3) For all experiments, first grey white, second yellow, third 

 orange. Last experiment, no orange. 



(7) For all experiments except last, first white, second yellow, 

 third orange. 



NO. I 169, VOL. 45] 



(S) For all experiments except la^t, first grey white, gradually 

 becoming warmer till it reached orange. 



(e) First white like phosphorus in the dark, gradually getting 

 to rose, and winding up with a reddish- orange not reached in 

 the last experiment. 



(C) First white with a dark shade, second yellow, third orange ; 

 no difference in any of the experiments except the last, where 

 the temperature was lower, and the orange was not reached. 



I may add that the temperature of the heating bar was a little 

 reduced each experiment, the colours changed very slowly, and 

 gave ample time for observation. A. NoiiLE. 



Poincare's " Thermodynamics." 



M. Tait ne repond pas a mon objection sous pretexte qu'elle 

 est sans importance. Je maintiens que nous n'avons aucun 

 moyen non seulement d'assigner I'origine des forces electro- 

 motrices Thomson, mais encore d'en constater I'existence. Si 

 M. Tait veut repondre, et s'il connait ce moyen, qu'il I'indique. 

 Dans le cas contraire, s'il n'est pas en mesure de soutenir une 

 quelconque de ses critiques, et s'il prefere un autre terrain de 

 discussion, je suis pret a I'y suivre. 



Seulement je serai force d'etre un peu plus long, car il me 

 faudra passer en revue les trois reproches de M. Tait. 



(i) La forme de mon ouvrage est trop mathematique. 



C'est la une appreciation personnelle dont il n'y a pas a dis- 

 puter. Je veux bien d'ailleurs d'une polemique surune question 

 de doctrine, mais non d'un proces de tendance ou je jouerais le 

 role d'accuse. 



Toutefois il est certain que je consacre relativement peu de 

 place a la description des experiences, et on aurait le droit des'en 

 etonner si je n'en donnais I'explication. Mon livre est la repro- 

 duction textuelle de mon cours ; or mes auditeurs avaient tous 

 suivi deja un cours de physique experimentale, oil ces experi- 

 ences leur etaient dccrites en detail. Je n'avais done qu'a leur 

 en rappeler brievement les resultats. 



(2) J'ai mal parle de la definition de la temperature absolue. 

 Autant que je puis comprendre, M. Tait ne trouve pas ma 



definition mauvaise, et n'en propose pas une autre ; mais, dit-il, 

 j'aurais du parler des experiences de Joule et Thomson, qui per- 

 mettent de mesurer la temperature absolue. 



Or j'ai decrit ces experiences a la page 164, et j'ai montre \ la 

 page 169 comment elles permettent de determiner la temperature 

 absolue. 



(3) J'ai laisse completement de cote une explication mecanique 

 du principe de Clausius que M. Tait appelle "the true (z.^. 

 the statistical) basis of the second Law of Thermodynamics." 



Je n'ai pas parle de cette explication, qui me parait d'ailleurs 

 assez peu satisfaisante, parce que je desirais rester completement 

 en dehors de toiUes les hypoUieses moleculaires quelque inge- 

 nieuses qu'elles puissent etre ; et en particulier j'ai passe sous 

 silence la theorie cinetique des gaz. H. PoiNCARE. 



Ornithology of the Sandwich Islands. 



Having just returned from an exploring expedition into the 

 interior of Australia, ou my way home I lingered in this group 

 of islands, and was sorry to find that .«ome species which have 

 been obtained here are now no longer to be found. 



My attention has been called to an interesting paper liy Prof. 

 Newton in your last issue (p. 465), on this subject, which seems 

 to imply that the ornithological collection made by Sir Joseph 

 Banks during his voyage in the Endeavour with Captain Cook 

 no longer exists, which I beg to be allowed to make a few 

 remarks upon. After the return of Sir Joseph Banks he had 

 several cases of birds carefully mounted and arranged according 

 to the localities in which they were collected. In one group of 

 land birds from Owhyhee, another case contained a number of 

 specimens from Botany Bay, conspicuous in the centre of 

 which was a very fine specimen of the Black Swan, which was 

 shot by Captain Cook himself. 



These cases were in the custody of the Linnean Society of 

 London until 1863, when they formed part of their Natural 

 History sale. 



These cases have been carefully preserved, and are now in 

 the museum of my ancestor, Mr. John Calvert, together with 

 a number of cases of birds which formed part of Sir Ashton 

 Lever's collection, amongst which are a few from the Pacific 

 Islands. These last cases were purchased from the executors of 

 the late Mr. M. Armfield, of Catherine Street, Macclesfield, 



