42 



KNOWLEDGE & SCIENTIFIC NEWS. 



[Febri'arv, 1907. 



thcrmo-clcmont, or a bolomctric arrnnRomont in combinn- 

 tion with a trlrphonc. The intormillomc indoclucod by lln- 

 til^lvcr is SI) threat that in the tclcphono a bif^h note is heard. 

 It is clainiftl that very fine tiiniiijjf can be cniploycd, witli llic 

 resultinfj ndvantajj^'e that neinhboiirinfi stations may br 

 closer loiifetlier without distiirbinjj^ one anollier. 



Time alone will show to what extent the claims of this 

 new system will be substantiated. In a leadinjj article in 

 the Wcciricinn (Oecember 21, iqob), which, in the main, is 

 eulogistic, there is a considerable amount of cautious 

 criticism of the claims and the methods of achieving them ; 

 and the opinion is expressed " that there need be no haste 

 in scr.ippintj plants at present in operation, and that il m;iy 

 vet be many y<>ars before the musical arc can sinjj the diri^e 

 of the spark." 



Mr. nuddell, in the last of his Christmas lectures lo 

 juveniles ;it the Roy.il Institution, showed such a sendini;' 

 anil receiviuij apparatus at work, and illustrated experi- 

 menl.illy the sh.irpness of tunintj which is nocessarv for 

 producing.;' the best effect. 



Disintegration Products of Actiniun^. 



The disinletjration series of acliniuni has been thoroui;blv 

 invesliijated by Dr. O. Ilahn, and the folUnvinfj six statues 

 have been determined :— 



The Monochroma.tism of the Red Cadmium 

 Spectrum Line. 



While .Micbelson's echelon grating' and also Fabrv and 

 Perot's interferometer indicated that the cadmium red line 

 was single, doubt had been thrown upon this result by the 

 fact that with Lummer and GchrcUe's apparatus it ap- 

 peared accompanied by several components. The doubt was 

 as to whether these components were real — in which case 

 the red light of cadmium would be a much more imperfect 

 source of pure light than had previously been hoped ; or 

 whether they were only ghosts or accidental appearances 

 arising from imperfectness in the apparatus employed. 

 This apparatus consists simply in a long parallel plate of 

 glass. A parallel beain of light is admitted in a very 

 oblique direction, and is internally reflected a large number 

 of times, a portion of it escaping at each reflection so as to 

 form an aggregate of parallel beams, between each of which 

 a certain phase-difference exists due to difference of re- 

 tardation in passing through the plate. A similar result 

 to this is produced in other interference apparatus, and 

 Lummer claimed great efiiciency for his particular arrange- 

 ment. Gehrcke and von Baeyer have now shown how to 

 distinguish between a ghost and a true component by the 

 use of an additional plate. The result of their test "is to 

 show that the apparent structure of the red line is wholly 

 due to ghosts, and therefore all the different interference 

 devices which are employed to test structure are now in 

 complete agreement. Similarly with regard to the green 

 mercury line. Lummer had obtained a much more com- 

 plicated structure than other observers. Here again, when 

 the new test is applied, the additional complication is .shown 

 to be spurious. It is very satisfactory to find the various 

 devices all leading to concordant results. In order to 

 indicate the superiority of interference apparatus over diffrac- 

 tive gratings it may be pointed out that no grating has 

 ever been ruled which is able to reveal the structure which, 

 with interference apparatus, is here being studied in detail. 



ZOOLOGICAL. 



By K. Lydekker. 

 is there a British Freshwater iVIcdusaP 



.\iu)i|- twenty jcars .ago it was iliscovered that certain 

 slieams in rhiladelphi.-i were inhabited by a small polyp, 

 which lives attached to stones at the bottom of Ihe water. 

 Twelve years later it w;is observed Ihat this Micmlttjilra, 

 ,-is il is called, reproduces itself by giving off free-swimming 

 jell\-lislKs or medusas. All this, it may be said, has 

 noliiing to do with a British jelly-lish. 'I'rue, but in certain 

 hot-house tanks there were at one time noticed small, fixed 

 jjolyps, then regarded as the sedentary stage of the free 

 jelly-fish previously obserNcd in llie Vidorin rcgia tanks in 

 the Regent's Park; and ihe suggestion now is, thai these 

 fixed polyps may possibly prove lo be indigenous British 

 representatives of the .American Micraliydra. Whether it is 

 worlh the while of amateur naturalists to commence 

 bunling for this problemalical creature must be left to the 

 (Ici'isicm of members of lh.-il liody. 



British Bears. 



Professor .S. II. R(\ Molds, of Bristol, has done much to 

 iricrease our knowledge of the bears which inhaliiled Ihe 

 British Isles during the Pleistocene and Prehistoric epochs, 

 in a memoir issued among the Palaontograijhical .Societv's 

 monogiaphs for 1906. The author fmds that all these bears 

 are closely related, but considers it advisable, on Ihe whole, 

 to retain the great cave-bear, Ursiis spctiiiis, as a distinct 

 species. All the rest he groups under the title of I'rxiix 

 (irrfiis, as typified by the brown bear of Scandinavia. Of 

 s()ecial imporlance is the opinion that the ri'ference of cer- 

 tain British (including Irish) bears to the .American grizzlv 

 {!'. a. horrihiU.*) cannot be substantiated. This is quite 

 in accordance with what might be expected from other con- 

 siderations ; for the grizzly bear (as now restricted) does 

 not occur in the higher latitudes of North America, where 

 its place is taken by races more nearly akin to the European 

 brown bear and its Asiatic representatives. If, then, any 

 of Ihe British bears exhibited marked resemblances to the 

 grizzly, it is obvious that such resemblances could only 

 indicate the existence in the British Isles of a race represent- 

 ing the American animal, and not that race itself. 



The Attis Spider. 



The Rev. O. P. Cambridge ])oints out in the Naturcilist 

 that the power of changing the colour of their eyes 

 possessed by certain spiders from Java (to which reference 

 was made in our last issue) is not a new phenomenon. The 

 same thing has been previously observed in other spiders 

 of the Attis family. 



Papers Read. 



.At the meeting of the Zoological Society on December 

 II, igo6, Messrs. J. Rennie and H. Wiseman contributed 

 a paper on the " Ascidians of the Cape Verde Islands," in 

 the course of which three species were described as new. 

 The arterial system of certain frogs and toads formed the 

 subject of a paper by Mr. L. K. Crawshay ; while fiftv-three 

 new African weevils were named and described bv Mr. G. 

 A. K. Marshall. Results of considerable morphological in- 

 terest were embodied in a paper by Mrs. O. A. M. Hawkes 

 on the cranial and spinal nerves of the shark Chlamydo- 

 sdachus. Two mammals, a cat and an elephant-shrew, 

 collected by Major Powell-Cotton in the Ituri Forest of 

 Central .Africa, were discussed by Mr. Lvdekker, who also 

 described a race of the bruang, or Malay bear, from Tibet. 

 Finally, Sir Charles Eliot furnished a supplemental com- 

 munication in regard to the nudibranchiate molluscs of 

 Southern India. 



At the meeting of the same Society on January 15, 1907, 

 the following papers were down for reading : — On a col- 

 lection of mammals from Annam, by Mr. T. L. Bonhote ; on 

 the " bleating " or " drumming " of the snipe, bv Mr. 

 P. H. Bahr ; on new or little-known marmosets from 

 .Amazonia, by Dr. E. A. Goeldi ; and on the classification 

 and anatomy of certain squamate reptiles (snakes and 

 lizards), bv Air. F. E. Beddard. 



