186 



KNOWLEDGE. 



[August 1, 1896. 



periodically cutting o£f a part of the star's light, seems to 

 account for the principal features of the phenomenon — 

 viz., a sudden diminution of light followed by a rapid rise, 

 more especially as the actual motion is revealed. ]?ut it 

 does not explain all. Repeated observation has shown 

 that the brightness of the star does not remain constant 

 after the minimum has been passed ; the old idea must be 

 given up that the light curve can be represented by a 

 straight horizontal line, with a sudden depression and 

 then a rccontinuation horizontally. j 



Duuer considers Y Cygni to consist of two equally large j 

 and bright companions and that the line of apsides revolves. 



A remarkable announcement has been recently made 

 that the spectrum of Altair (hitherto free from all suspicion 

 of variation) shows peculiarities from which it is inferred 

 that the star is a " spectroscopic triple," the two secondary 

 bodies being dark as compared with the principal. Prof. 

 Pickering foreshadowed this result some time before in a 

 paper on the discovery of double stars by means of their 

 spectra. 



The Variable Stars, Southern Hemisphere. Algol Stars thus : G 



Enough has been said to show how incomplete is our 

 knowledge of the variable stars — yet that knowledge is 

 advancing with such rapid strides that we may hope to 

 obtain clearer views as time goes on ; and when the 

 problem of variable stars is solved a great step will be 

 made towards that knowledge of the constitution of the 

 heavens which Sir W. Herschel, Proctor, and others have 

 so earnestly sought after. 



Since the above was written the work of discovery of 

 variable stars goes on apace, and Prof. Pickering announces 

 ten new ones in Harvuid CuUcfie (Jhncrvatonj Circular, No. 7, 

 of which one was previously noted by the writer. The 

 Professor also finds that S Antlias is not of the Algol type, 

 but that its light is continually changmg after the manner 

 of S Cephei and i; Aquilie. 



OUR FUR PRODUCERS.-IV. 



FUR-SEALS. 



By R. Lydkkker, B.A.Cantab., F.R.S. 



PROBABLY there are still to be found persons who 

 believe that " sealskin " is the product of our 

 common British seals ; and it is, therefore, well 

 to state at once that this is not the case. It is 

 true that the fur of an ordinary seal has much the 

 same appearance as that of a fur-seal when in it3 natural 

 state, but the former lacks the fine, soft, woolly under-fur 

 which alone constitutes the sealskin of commerce. To 

 remove the upper fur, the skin was formerly always, and 

 still is frequently, shaved on the lower surface ; and as the 

 long hairs are more deeply emplanted than is the under-far, 

 their roots are cut away by this process, and the hairs them- 

 selves can then be brushed out. This process is techni- 

 cally known as "pulling"; and visitors to the Natural 

 History Museum at South Kensington may see, in 

 one of the bays on the left side of the entrance- 

 hall, sealskin before and after it has been subjected 

 to this process. After the removal of the long 

 hairs the sealskin is dyed and curled, and is then 

 ready for use. Seals that yield commercial seal- 

 skin differ from ordinary or true seals [I'horida) 

 in many points — notably in the retention of small 

 external ears, and in the circumstance that, when 

 on land, the hind flippers are bent forwards 

 beneath the body, instead of being stretched 

 straight out behind. It must not, however, be 

 supposed that all the eared seals (as the members 

 of the family Otariida are best termed) yield 

 commercial sealskin. On the contrary, many 

 have only the long hairs without any of the woolly 

 under-fur, and are consequently spoken of as 

 hair-seals, in contradistinction to fur-seals. Not 

 the least curious feature in connection with this 

 difference is that hair-seals and fur-seals are 

 found inhabiting the same districts, showing that 

 the presence of under-fur does not depend by 

 any means on the latitude of the habitat of the 

 animals. 



Although the price of the individual pelts 



is comparatively small, the enormous number 



brought into the market renders sealskin probably 



the most important item in the whole fur trade ; 



and when it is stated that up to 1889 upwards 



of one hundred thousand fur-seals were killed 



annually on the Prybiloffs alone, while in 187i 



about four and a half million individuals were 



computed to visit those islands, some faint idea 



may be obtained of the magnitude and importance of the 



trade. Human greed has, however, done its best to 



ruin this trade by indiscriminate and reckless slaughter ; 



and from many parts of the world where fur-seals formerly 



swarmed they have now been more or less completely 



exterminated. 



The habits of the fur-seals, and the numbers in which 

 they formerly resorted to their "rookeries" during the 

 breeding season, have been so frequently described that it 

 will be quite unnecessary to allude to them further in the 

 present article ; and it will accordingly sufKce to notice 

 the species of most importance in the fur trade, with some 

 remarks on the number and value of the pelts annually 

 obtained. 



Foremost among these is the northern sea-bear, or 

 Alaska fur-seal {Otaria wsina), characterized externally by 



