28o 



NATURE 



[July 21, 1898 



Mrs. Wallace ; a Lion {Felis ho, 6 ) from North Africa, pre- 

 sented by Mr. P. B. Vanden Byle ; a Grey Parrot {Psiltactis 

 erithacus) from West Africa, presented by Mr. Palmer; a 

 Cardinal Grosbeak {Cardinalis virginianus) from North 

 America, presented by Mrs. Chambers ; two Shags [Phalacro- 

 corax graculus) from Scotland, presented by The Maclaine of 

 Lochbuie ; three European Pond Tortoises [Etnys orbicularis) 

 from Italy, presented by Miss E, Endicott ; two Axolotls 

 {Amblystoma tigrinum) from Central America, presented by 

 Mr. W. R. Temple ; a Chameleon [ChanttEleon vulgaris) from 

 North Africa, presented by Mr. Clyde Hinshelwood ; . two 

 Common Snakes (Tropidonotus natrix) from Germany, pre- 

 sented by Mr. A, Waley ; two Orang-outangs {Simla 

 satyrus, i 9) from Borneo, a Squirrel Monkey {Chrysothrix 

 sciurea) from Brazil, a Gentoo Penguin {Pygosceles iceniatus) 

 from the Falkland Islands, a Maguari Stork {Dissura maguari) 

 firom South America, two Thick-billed Penguins {Eudypies 

 pachyrhynchus) from New Zealand, a Jardine's Parrot {Pceo- 



cephalus gulielmi) from West Africa, two Honey- eaters 



(Ptilotis, sp. inc.) from Australia, two Elephantine Tortoises 



{Testudo elephantitia), a Tortoise [Testiido, sp. inc.) from 



the Aldabra Islands, deposited ; five Bridled Wallabies (2 <J , 3 ? ) 

 from Australia, five Ruffs {Machates pugnax), two Redshanks 

 (Totanus calidris), two Spoonbills {Platalea leucorodia), 

 European, ten Common Chameleons {Chamaleoii vulgaris) 

 from North Africa, purchased ; a Macaque Monkey {Macacus 

 cynomolgus), two Japanese Deer {Cervus sika, (J 9 ), born in 

 the Gardens. 



OUR ASTRONOMICAL COLUMN. 



Comet Perrine (June 14). — The following is the ephemeris 

 for comet Perrine for the ensuing week : — 



1898. R.A. Decl. Br. 



h. m. s. o / 



July 21 ... 6 38 7 ... +3852-3 ••• 3*96 



22 ... 42 6 ... 37 580 



23 ... 46 4 - 37 2-6 



24 ... 49 59 ... 36 5-9 



25 - 53 51 ••• 35 8-1 ... 4-67 



26 ... 57 41 - 34 9*1 



27 ... 7 I 29 ... 33 8*9 



28 ... 7 5 16 ... 32 7-5 



A New Form of Grating Spectroscope. — Prof. Michel- 

 son describes, in the Astrophysical Journal for June, a spectro- 

 scope which seems specially adapted for examining any particular 

 line in a spectrum. The idea is that in a grating it is desirable 

 sometimes to be able to throw a large proportion of light into 

 very high orders of spectra — the hundredth, for example — and 

 according to the arrangement here adopted the method seems 

 quite simple. The problem becomes still more simple if the 

 grating be arranged for transmission, as the grating can then 

 be efficiently constructed if one can make a considerable number 

 of plane-parallel plates of glass of the same thickness. Using only 

 seven elements — that is, seven of these plates of glass arranged 

 in step fashion — and placing them between a collimator and an 

 observing telescope, and the collimator slit illuminated by a 

 sodium flame, the broadening of the lines could be easily de- 

 tected, and the Zeeman effect readily observed when the sodium 

 flame was placed in a magnetic field. The resolving power of 

 this instrument being independent of the number of glass plates, 

 but depending 'only on the total thickness, the only advantage 

 gained in using a large number of elements is that the spectra 

 are more separated. With a few elements the spectra over- 

 lap ; but this, as is pointed out, does not make much difference 

 if effects of broadening, shifting or doubling of single lines be 

 alone attempted. A spectroscope with twenty elements has 

 already been in use in the Ryerson Physical Laboratory, and 

 Prof. Michelson is now having another constructed giving 

 greater resolving power, and sufficient for the analysis of close 

 groups of lines. 



Structure of the H and K Lines.— Mr. Jewell tells 

 us {Johns Hopkins University Circular for June) that while 



NO. 1499, VOL. 58] 



examining a series of photographs of the solar spectrum made 

 by Prof. Rowland in 1888 and 1889, he discovered one plate oi> 

 which the shading of the H and K lines of calcium was brokei> 

 up into bands or series. These bands were noticed to begin at 

 the centre of the shaded lines and extend outward, the distance 

 between the component lines of the series increasing as the 

 distance from the centre increased. Further, the series were 

 perfectly symmetrical about the centres about H and K, and 

 the individual lines or components somewhat nebulous, while 

 nearly all the other lines in the same region were sharp and 

 clear. Since that date Mr. Jewell has not been able, except 

 quite recently, to detect this peculiarity in the photographs 

 taken by himself ; but, on March 1 1 last, a plate was exposed to 

 the arc spectrum of calcium (x 4000) under somewhat special 

 conditions, and this showed the shading broken up into series. 

 The shading on the red side of H was quite distinctly broken 

 up into series similar to those of the solar spectrum mentioned 

 above. The series on the violet side was not so distinct ; while 

 the shading is better on the violet side of K than on the red 

 side. Mr. Jewell further says that the resolution into lines is 

 hardly perceptible close to the principal line, but is fairly dis- 

 tinct about three Angstrom' units from H. Curiously enough, 

 the lines of the series in the arc spectrum plate are reversed ; 

 but some distance away from the central lines it is probable that 

 they are continued as emission lines. 



To obtain this negative an extremely powerful direct electric 

 current was used, being allowed to act for a short time before 

 the image of the poles was thrown on the slit of the spectro- 

 scope, the length of exposure being three to four seconds. In 

 this way the calcium was highly volatilised, and the "highly 

 heated vapour formed a much more extended atmosphere 

 around the poles than with a weaker current ; and it is also 

 possible that the conditions throughout the larger part of the 

 arc were more uniform than under ordinary circumstances." 

 Mr. Jewell thinks that, in the case of the solar spectrum referred' 

 to, the slit of the spectroscope probably covered a region of the 

 sun's atmosphere where the principal layer of the calcium was 

 of a particular density, and being thus to a degree isolated was 

 able to produce its characteristic series. This, he says, is 

 somewhat confirmed in that the general shading of H and K on 

 the plate is unusually weak. 



Blurring Aberration in the Telescope. — In the note 

 which previously appeared in this column (May 26, p. 88), 

 we referred to Mr. Collins' paper on this subject, and remarked 

 that the tilting of the image not only occurs in the case of the re- 

 flector, but in that of the refractor also ; the effect in the latter case 

 being twice as great as that in the former. We should, however, 

 have made it clearer if we had stated that the tilt is really the 

 same in both instruments of like angular aperture, but the 

 difference in the inequality of size of the images formed from the 

 " marginal " and "central" portions of aperture focussed on a 

 single focal plane is twice as great in the ordinary refractor as 

 with the reflector. The images formed from the central portioii 

 of the reflector are smaller than those formed by the marginal 

 rays, while with the refractor the marginal rays produce smaller 

 images than the central rays passing through the lens. 



THE LIFE-HISTORY OF THE SALMON} 

 nPHE investigations recorded at length in this Report are partly 

 ■*■ of biological, partly of more purely physiological interest. 

 They were undertaken with the following objects : — 

 (i) To elucidate some of the factors governing the migration 

 of the salmon, and to study the course of these migrations. 



(2) To determine whether or not Miescher is right in his con- 

 tention that salmon do not feed during their sojourn in fresh 

 water. 



(3) If salmon while in the river do not procure an abundance 

 of food, to investigate from what source they obtain the energy 

 for the large amount of muscular work they perform, and 

 whence comes the material to build up the enormous genitalia 

 which are developed before spawning. Such an investigation 

 must necessarily yield information of interest as to the chemical 

 changes of various substances in the animal body. 



1 " Report of Investigations on the Life-History of the Salmon in Fresh 

 Water." From the Research Laboratory of the Royal College of Physicians 

 of Edinburgh. Edited by D. Noel Paton, M.D., Superintendent of the 

 Laboratory. A Report to the Scottish Fishery Board presented to Par- 

 liament by command of Her Majesty. (John Menzies and Co., Edinburgh ) 



