October 6, 1898] 



NATURE 



547 



of fuchsin, and had been experimentally investigated with 

 great power by Kundt.^ 



Sellmeier himself somewhat marred ^ the physical 

 value of his mathematical work by suggesting a distinc- 

 tion between refractive and absorptive molecules (" re- 

 fractive und absorptive theilchen"), and by seeming to 

 confine the application of his formula to cases in which 

 the longest of the molecular periods is small in com- 

 parison with the period of the light. But the splendid 

 value of his formula for physical science has been quite 

 wonderfully proved by Rubens (v/ho, however, inadver- 

 tently quotes'' it as if due to Ketteler). Fourteen years 

 ago Langley * had measured the refractivity of rock-salt 

 for light and radiant heat of wave-lengths (in air or ether) 

 from 43 of a mikron to 5-3 mikrons (the mikron being 

 lo" of a metre, or lo"^ of a centimetre), and without 

 measuring refractivities further, had measured wave- 

 lengths as great as 1 5 mikrons in radiant heat. Within 

 the last six years measurements of refractivity by Rubens, 

 Paschen, and others, agreeing in a practically perfect 

 way with Langley's through his range, have given us 

 very accurate knowledge of the refractivity of rock-salt 

 and of sylvin (chloride of potassium) through the 

 enormous range of from '4 of a mikron to 23 mikrons. 



Rubens began by using empirical and partly theoretical 

 formulas which had been suggested by varioos theoretical 

 and experimental writers, and obtained fairly accurate 

 representations of the refractivities of flint-glass, quartz, 

 fluorspar, sylvin, and rock-salt through ranges of wave- 

 lengths from "4 to nearly 12 mikrons.^ Two years later, 

 further experiments extending the measure of refractiv- 

 ities of sylvin and rock-salt to radiant heat of wave-lengths 

 up to 23 mikrons, showed deviations from the best of the 

 previous empirical formulas increasing largely with in- 

 creasing wave-lengths. Rubens then fell back " on the 

 simple unmodified Sellmeier formula, and found by it a 

 practically perfect expression of the refractivities of those 

 substances from "434 to 22*3 mikrons. 



And now for the splendid and really wonderful con- 

 firmation of the dynamical theory. One year later a 

 paper by Rubens and Aschkinass ' describes experiments 

 proving that radiant heat after five successive reflections 

 from approximately parallel surfaces of rock-salt and 

 again of sylvin, is of mean wave-length 5 1*2 and 61 "i 

 mikrons respectively. The formula which Rubens had 

 given in February 1897, as deduced solely from refrac- 

 tivities measured for wave-lengths of less than 23 

 mikrons, made \r- negative for radiant heat of wave- 

 lengths from 37 to 55 mikrons in the case of reflection 

 from rock-salt, and of wave-lengths from 45 to 67 mikrons 

 in the case of reflection from sylvin I (/i"^ negative means 

 that waves incident on the substance cann ot enter it, but 

 are totally reflected). 



A FOURTH SPECIMEN OF ''NO TORN IS 

 MANTELLi;' OWEN. 



NATURALISTS in New Zealand have this week 

 been thrown into a great state of excitement by 

 the capture of the fourth entire specimen of this very 

 rare flightless Rail. 



On .\ugust 8 I received a telegram informing me of 

 the acquisition, and asking advice as to its preservation. 

 Fortunately, a skilled taxidermist is attached to the 

 Otago Museum, and I was able to arrange that the bird 



1 Kundt, Pog^. Ann., vols. 142, 143, 144, 145, 1871-72. 



2 Pogg. Ann,, vol. 147, 1872, p. 525. 



3 Wied. Ann.,\o\. 53, 1894, p. 267. In the formula quoted by Rubens 

 from Ketteler, substitute for fteo the value of ^L found by putting t = 00 in 

 Sellmeier's formula, and Ketteler's formula becomes identical with Sell- 

 meier's. Remark that Ketteler's " M " is Sellmeier's " mtC- " according to 

 my notation in the text. 



■* Langley, P/ii/. Mag., 1886, 2nd half-year. 



8 Rubens, U^iei/. Ann., vols. 53, 54, 1894-95. 



6 Rubens, Wied. Ann., vol. 60, 1896-97, p. 454. 



" Rubens and Aschkinass, Wied. Ann., vol. 64, 1898. 



NO. I 5 10, VOL. 58] 



should be sent to that institution : it arrived two days 

 later, and its remains are now in my care. 



The last specimen of Notornis was captured twenty 

 years ago ; and it was almost universally considered by 

 Maories, as well as by whites, to be extinct ; hence the 

 interest that attaches to the present specimen. 



It may not be uninteresting to naturalists at home to 

 be reminded of some facts in the history oi Notornis as 

 recorded in Buller's " Birds of New Zealand." The 

 name was originally bestowed by Owen on some fossil 

 bones discovered in the North Island, New Zealand. 



Some years later (1849), Mr. W. Mantell was able to 

 secure a freshly killed specimen, taken in the south-west 

 of the Middle Island (the southern of the two main 

 islands of New Zealand). This bird, the skin of which 

 is in the British Museum, was declared by competent 

 ornithologists at home to be identical with the fossil 

 form. The second specimen was killed by Maories in 

 185 1, and its remains are also in the National Collection. 

 The third specimen was obtained nearly thirty years 

 later, in 1879, and was purchased for the Dresden 

 Museum. (From an e.xamination of the bones Dr. A. B. 

 Meyer declared it to be distinct from the fossil form, and 

 named it A^. hochsteiteri.) These three specimens were 

 killed at three spots about 100 miles apart, in very 

 rugged country. Later, an incomplete skeleton was 

 discovered, which is at present in the Otago Museum. 



The bird recently killed is thus the fourth specimen 

 seen in the flesh, and its future fate is at present 

 uncertain. It was killed by a dog in the bush adjoining 

 Lake Te Anau, in the same district as the other three 

 specimens. 



I have examined and made sketches of its viscera, 

 which, like all parts of the bird, are carefully preserved 

 for the owner. The specimen is a young female, in 

 excellent health and splendid plumage. 



During the present month I have been fortunate 

 enough to obtain, on deposit, an egg of the Moa — the 

 third or fourth, I believe, in anything like a complete 

 condition. Although the egg is much broken, one side 

 remains practically complete ; the pieces of the other 

 side had fallen inwards, and are embedded in the sand 

 within the shell. The egg was discovered in a sandy 

 deposit, and when it reached me was partially enveloped 

 in sand. This has been removed, as far as safety would 

 permit, from the more complete side of the egg, and 

 the whole was thoroughly soaked in weak gelatine to 

 bind sand and shell together. The specimen closely 

 agrees in size and shape with the cast, which is familiar 

 in all museums, and alongside of which it is now on 

 exhibition. As in the case of the eggs previously dis- 

 covered, it was one of a pair ; the other was unfortunately 

 broken, on handling, by those concerned in its ex- 

 cavation. W. Blaxland Benham. 



Dunedin, August 14. 



A LIVING REPRESENTA TIVE OF THE OLD 

 GROUND-SLOTHS. 



ALL naturalists will unite in congratulating Sefior 

 Plorentino Ameghino on the remarkable discovery 

 it has been his good fortune to make. It appears that 

 several years ago he was informed by Ramon Lista — a 

 traveller in Patagonia— of an encounter with a strange 

 nocturnal beast, which, after being fired at and apparently 

 hit, succeeded in escaping unharmed. It was described 

 as like an Indian pangolin in size and form, but with the 

 skin covered with greyish red hairs instead of scales ; 

 and from the rapidity with which it disappeared among 

 the bushes, seemed to have been an animal of compar- 

 atively active habits. Till quite recently, nothing more 

 had ever been heard of the strange creature seen by 

 Lista in Santa Cruz ; most of those to whom the story 



