11 



KNOWLEDGE 



[Janlaby, 1902, 



Astronomical. — Several attempts have been made to 

 ascei-tain the date of the original construction of 

 Stonchengo from astronomical considerations, but 

 hitherto the adopted data appear to have lacked the 

 precision which is necessary in calculations depending 

 upon the secular variation of the obliquity of the 

 ecliptic. There is every indication that one use of the 

 structure was to mark the direction of sunrise at the 

 summer solstice, and it is evident that if this direction 

 can be determined the departure from it of the present 

 point of sunrise will furnish material for an estimation 

 of the date. In a paper recently communicated to the 

 Royal Society, Sir Nonnan Lockycr and Mr. F. C. 

 Penrose give particulars of observations made last year 

 which have led them to fix the date at about 1680 B.C. 

 The adopted azimuth of the axis is 49° 34' 18", and 

 the elevation of the local horizon 35' 30" ; it has 

 further been supposed that the sun's upper limb was 

 2' above the horizon when the observations were made, 

 this estimate being based upon an actual observation 

 of sunrise made on June 25th. It is notable that 

 implements which have been discovered since the above 

 obsei-vations were made also indicate a fairly accordant 

 date. 



The probability that the solar corona consists largely 

 of particles capable of reflecting the light of the photo- 

 sphere has been greatly strengthened by the obsei-vations 

 of the eclipse of last May. The evidence of polarisation 

 obtained by Mr. Newall has been fully confirmed by 

 the work of the pai-ty from the Lick Observatoiy, and 

 the Lick obsei-vers have also established the presence 

 of Fraunhofer lines in the spectioim of the outer corona 

 by using instruments of low dispersion. The continuous 

 spectrum of the inner corona is readily accounted for 

 by supposing the particles to be incandescent in the 

 immediate neighbourhood of the photosphere. It there- 

 fore seems reasonable to suppose that the coronal 

 streamers consist of finely-divided particles of matter 

 ejected with great velocity from the siu-face of the 

 sun. The observations of all the eclipses since 1893 

 indicate that the part of the corona giving a gaseous 

 spectrum is relatively very shallow. 



Further details given in Lick Observatory Bulletin 

 No. 10 appear to leave little doubt as t-o the reality of 

 the enonnous proper motion of four condensations in 

 the nebula surrounding Nova Persei. The result was 

 arrived at by comparing a photogi-aph taken on 

 November 7th with one taken 48 days earlier at the 

 Yerkes Observatory, from which it appears that the 

 movement is at the rate of 11' a year, and is certainly 

 not radial. It is probable tJiat the nebula is intimately 

 connected with the Nova, and it does not seem unlikely 

 that a study of their relationships will throw much light 

 on the origin of new stars.- — A. F. 



Botanical. — The function of crystals of calcium 

 oxalate in plants ia discussed in the current volume of 

 the Botanical Gazette by Dr. A. Schneider. The com- 



monly accepted theory is that these crystals protect the 

 plant against herbivorous animals, cither in consequence 

 of an unpalatable taste which they are supposed to im- 

 part to the herbage, or of mechanical interference. It 

 IS shown that calcium oxalate is dissolved with difficulty, 

 being insoluble in water, alcohol, ether, acetic acid, 

 saliva, and other animal secretions, and is, in these 

 substances, tasteless. It is therefore inferred that taste 

 docs not repel animals. Protection by mechanical means 

 is thought to be improbable from the way in which the 

 crystals are distributed through plant-tissues. Instead 

 of being confined to peripheral parts, where their effects 

 would bo most pronounced, they are often abundant in 

 tho pith and hcartwood of stems. Kraus in 1891 sug- 

 gested that calcium oxalate was a resei-ve product, which 

 would be re^dissolved and again utilised by tho plant. 

 This, Dr. Schneider believes, is its secondary function, 

 the primai-y one being that of mechanical support as 

 exemplified in parts of certain plants where sclereu- 

 chymatous tissue is replaced by crystal-bearing cells. 



In the Indian Forester for October, 1901, Sir Dietrich 

 Brandis draws attention to two Burmese aromatic woods, 

 one of which (Cordia frogratifissima) is the som"ce of a 

 cosmetic and perfume used by Burmese ladies. It has 

 a brown, vei-y hard hcartwood, which is strongly 

 aromatic, differing in this respect from that of allied 

 species, in one of which, however, it is slightly scented. 

 The other wood is produced by a close ally of Santaluin 

 album, the sandal-wood tree, but differs in having longer 

 meduUai-y rays and a dark olive-brown heartwood. — 

 S. A. S. 



Zoological. — So far as mammals are concerned, the 

 most important event we have to chronicle is the arrival 

 at the Duke of Bedford's park, Wobum Abbey, of a 

 drove of Przewalski's horse (Equiis przewahkii), from 

 the deserts of Mongolia. Although this species was 

 described twenty years ago, no specimen has hitherto 

 reached England, and naturalists have been veiy im- 

 perfectly acquainted with its affinities, and have had 

 doubts whether it was really entitled to rank as a 

 species. In spite of being colts, the specimens at 

 WobruTL Abbey demonstrate the distinctness of this 

 most interesting member of the equine famdy, and show 

 that it is more nearly related to the horse than to the 

 wild asses, although presenting some resemblance to the 

 latter. In general appearance the colts are not unlike 

 New Forest ponies, although their white muzzles give 

 them a somewhat asinine appeai'ance. They ai'e dun- 

 colovu-ed, with black points, and show in most cases no 

 dark stripe down the back. They have, like the horse, 

 "chestnuts" on all four legs; but the long hairs on 

 the tail do not commence quite so high up as in that 

 species. 



Dr. A. Nehring, of Berlin, has recently described (in 

 Globus) the skull of a large fossil camel from Russia, 

 which he believes to be the ancestor of the living two- 

 humped Bactrian species. These two species appeal', 

 indeed, to be natives of Central and Northern Asia, and 

 are essentially adapted for a cold climate. The one- 

 humped Arabian camel, on the other hand, seems to 

 have originated in tropical or subtropical regions. 



American naturalists are devoting much attention to 

 the restoration of tho external bodily form of extinct 

 animals; and in tho Smithsonian Report for 1900 

 Mr. F. A. Lucas, of the U. S. National Museum, has 

 published an interesting paper dealing with the history 

 of the subject. The attempts at restoration by Cuvi'er 

 in Paris and Waterhouso Hawkins at the Crystal Palace, 



