482 



KNOWLEDGE & SCIENTIFIC NEWS. 



[July, 1906. 



that it became partially involved in a great melting process, 

 consequent on the rise of a heated liquid zone, and the fold- 

 ings assume a morc-to-bc-expectcd aspect. In the rise of 

 such a zone, strata would not necessarily lose its stratified 

 form, although it would become of a plastic consistency. 

 All kin<ls of gradations would Jifterwards appear in such 

 rocks when they again cooled, and these would give rise to 

 those metamorphosed rocks which it is impossible to classify 

 either as igneous or sedimentary. 



Why Lava Rises in a Volcano. 



Occassionall}' portions of sedimentary rocks are erupted 

 from a volcmo, but with these very occasional exceptions 

 the lava, scorias, &c., which are erupted, and those intru- 

 sive rocks which do not reach the surface, may be held to 

 represent part of the original, unaltered, material of the 

 globe. Water plays the part of the explosive agent, and in 

 later stages may assist in the welling of the material up the 

 volcanic neck, after a rupture has been made, and a weak 

 spot has thus been discovered. DifTerent kinds of igneous 

 rocks may be due to an actual stratified arrangement of 

 molten material brought about by differences in specific 

 gravity, .at some time subsequent to the original condensa- 

 tion of the globe. There must, however, be some stress or 

 strain to produce the necessary pressure or squeezing power 

 for the upward flow, and no cause has so far been dis- 

 covered other than that furnished by the secular cooling of 

 the planet. 



ORNITHOLOGICAL. 



By W. P. PvcRAFT, A.L.S., F.Z.S., M.B.O.U., &c. 

 Jackass Penguins on Dassen Island. 



At the last meeting of the ISritish Ornithologists' Clul), Mr. 

 Meade Waldo — who with Mr. M.J. XicoU accompanied Lord 

 Crawford on his winter cruise in his yacht the " Valhalla " in 

 the capacity of naturalist — gave a most interesting account of 

 the vast breeding colony of the Jackass Penquin on Dassen 

 Island off the Cape of Good Hope, and commented on their 

 extraordinary tameness. Though this colony was estimated 

 to contain about 40,000 birds, it would seem that its ultimate 

 extinction is within a measurable distance, since the eggs of 

 these birds are transported annually in enormous quantities 

 to the mainland. 



Cape Cormorants were also breeding herein thousands; but 

 they are carefully protected for the sake of the guano. On 

 this account the presence of Sacred Ibises in their midst is 

 regarded by owners of the island as objectionable, since they 

 prey, or are believed to prey, on the young Cormorants. They 

 are also said to live on the food brought by the Cormorants 

 for their young, though how this is obtained was not apparent. 



Migration of Swifts. 



Colonel Verbury at the meeting just referred to called 

 attention to the enormous flocks of Swifts and Swallows which 

 gather at Torcross in South Devon on their southerly migration. 

 From August 5 onwards, for about a fortnight. Swifts are to be 

 seen here in hundreds, and after their departure Swallows 

 assemble here in thousands. 



We draw the attention of our readers to this spot, since those 

 interested in migration will probably find a rare opportunity 

 of adding to our knowledge of this mysterious instinct, by a 

 stay in this neighbourhood. 



Curious Nesting Place of a Goosander. 



Herr 2ollikofer in a recent number of the ScliweizeriscJie 

 Blatter Jiir Oriiithologic describes a case of a Goosander 

 which nested in a hole in the roof or tower of a manor 

 house at Werderberg. The height of the tower is 100 feet, 

 and the young were in due time brought down to the ground 

 in safety by the parent — it is supposed in her bill. 



Blue-Throated Warbler in Norfolk, 



The Kev. M. C. H. Bird writes to the Field, May 26, to s.ay 

 that he saw, several times during the 1 6th- 17th May, a Blue- 

 throated Warbler in the neighbourhood of Hickling Broad. 

 As this bird, during the autumn at any rate, is fairly connnon 

 during certain years in parts of Norfolk, it is possible that, if 

 unmolested, spring migrants may be induced to breed here. 



Pallas's Sand-Grouse in East Lothian. 



.According to a note by Mr. C. S. Chambers in the Field, 

 June 2, a flock of six Pallas's Sand-Grouse (5)' (T/(n/'ta/i((ra!/y.v!(s) 

 was flushed by him when playing golf over well-known links in 

 East Lothian. There seems no reason to doubt the accuracy 

 of this record, especially after the description of the birds 

 which supplements this note. They would appear to have 

 been frequenting this ground for some time, and to have been 

 seen on several occasions by one of the " caddies." 



Fire-Crest Nesting in Skye. 



The Field, June 16, contains a note by the Rev. 1). De 

 Mackinnon on the nesting of the Fire-crested Wren in Skye. 

 On May 19 the writer saw a bird of this species sitting on her 

 nest near Portree, and since then it seems three other nests have 

 also been found. The " hen bird being very tame every oppor- 

 tunity was afforded of observing her on the nest." But for this 

 assurance we should have felt inclined to believe that the Gold- 

 crest had been mistaken for its rarer ally. And even now we 

 cannot resist a suspicion that some mistake may after all have 

 been made. 



PHYSICAL. 



By Alfred W. Porter, B.Sc. 



On Japanese Mathematics. 



The following is from a paper by Professor Harzer, read 

 last Near before the M;ilhematical and Ph\sical Section of 

 the British Association, the .Annual Report of which has 

 just been issued : — " Concerning the Japanese numerical 

 value of TT, that is to say of the ratio of the circumference of 

 the circle to its diameter, we have knowledge of the fraction 

 79/25, about the year 1627. On expressing this value in 

 the decimal system of numbers, in use in Japan since olden 

 times, the first two places are right. To the second half 

 of the 17th century belong decimal values of the precision of 

 9 and 10 places. About 1709, there is to be found the 

 famous fraction, 355/113, right to 7 places, and about 

 1722 and 1739, the precision increases to 42 and 51 correct 

 places. Moreover, about 1766, the two common fractions 



.S4I93SI „ , 4^8^^4593349304 



— ana — 2 — 5 



1725033 , 1363055121570117 



were known, representing n with astonishing precision 

 to 12 and 30 places; and already about 1760 there exists 

 the value, 98548/9985, for tt- which is exact to 9 places." 



The Black Spots in thin Liquid Films. 



It is gintrally assorted that very thin films beh.'ive as 

 pcrfecliy transparent bodies, that is, that all the light is 

 ttansmitted, and in consequence none is reflected. But 

 Dr. Johannott has shown that there is more than one 

 " black." The first found varied in thickness between 

 40 ;t,u and i2Ayu. The first black was found to break naturally 

 into the other when the atmosphere was incompletely 

 saturated. With a thoroughly enclosed film, it was 

 necessary to heat the system in order to form the second 

 black film, which had apparently a constant thickness of 

 6 ixfj. in all cases. 



Recently (Philosophical 2Iaqazine, June, 1906), he has 

 discovered that great changes in the character of these 

 films could be produced by changing the pressure on the 

 atmosphere surrounding the films. A sudden increase in 

 the pi'essure was accompanied by a rapid thinning of the 

 film while on the other hand a sudden diminution of the 



