June 27, 1895] 



NA TURE 



203 



at 20° C, and confined in the reaction tube by mercury, gave a 

 continuous absorption which appeared to go on indefinitely. 

 The product contained mercury, but gave no reaction for sulpho- 

 cyanide. When heated, a quantity of gas was recovered equal 

 to about one half the volume absorbed, and this recovered gas 

 was proved to be argon by condensation with benzene, and 

 production of the remarkable fluorescence previously described. 

 Though this work has been done on such small quantities of 

 material that an e.xhaustive examination of the product was not 

 possible, M. Berthelot believes that he has satisfactorily demon- 

 strated the significant property of argon, that it can enter into 

 combination and be regenerated from its compound or com- 

 pounds with its initial properties intact. 



As a result of observations carried on by the Iiivestigalor in 

 the autumns of 1892-3-4, Commander C. F. Oldham, R.N., 

 contributes two papers on the Laccadive Islands to the Journal 

 of the Asiatic Society of Bengal (vol. Ixiv. pt. ii. No. I, April 

 1895). T'l^ gfoup consists of four submerged coral-reefs, six 

 reefs with small islets (" sand-cays"), and eight inhabited atolls : 

 three of the reefs and five of the atolls were examined. The 

 islands and sand-cays occur, in all cases but one, on the eastern 

 side of the atolls ; they cannot, therefore, have been built up by 

 the action of the ordinary monsoon winds which blow mainly 

 firom the west, but must be due to the occasional hurricanes 

 which reach the eastern and north-eastern sides of the atolls. 

 The effect of the tides and currents is seen in the more vigorous 

 growth of the atolls to the south and west. The islands and 

 islets are extending at their extremities, and in some cases are 

 being added to on the south-western sides where they face the 

 lagoon. No evidence of either elevation or subsidence was 

 observed. 



The additions to the Zoological Society's Gardens during the 

 past week include a Rhesus Monkey {Macacus rhesus, 9 ) from 

 India, presented by Mrs. Stevens ; two Javan Parrakeets 

 (Palteornis javanica) from Java, presented by Lieut. -General 

 Sir H. B. Lumsden ; a Green-winged Trumpeter (Psophia 

 viridis) from Brazil, presented by Mr. H. A. Astlett ; a 

 Diamond Snake {Morelia spilotes) from Australia, presented by 

 Mr. M. Mitchcner ; a Natal Python (/^///ck nalalensis) from 

 South Africa, presented by Mr. William Norman ; a Korin 

 Gazelle (Gazella ritfifrons,'} ) from Senegambia, a Blue and 

 Yellow Macaw (Ara aiaraiina) from South America, a Naked- 

 necked Iguana {Iguana delicatissima) from Tropical America, 

 thirty-four Black Salamanders (Salaniandra aira). South 

 European, deposited ; a Tachiro Goshawk (Asltir tachiro) from 

 South .\frica, nine Red-beaked Weaver-Birds ( (^;«.7fij .(«Hy«j«j- 

 rastris) from West Africa, jiurchased ; a White-crested Jay 

 Thrush {Garrulax leucolo/hus), a StriAlcd]a.y Thrush (Gramma- 

 toptila striata) from India, received in exchange ; a Burrhel 

 Wild Sheep (Ovis burrhel,'}), a Patagonian Cavy (Dolichotis 

 patachonica), born in the Gardens. 



OUR ASTRONOMICAL COLUMN. 



The Yerkes Ouservaiory.— From a note in the -J.c/ra- 

 physical /ournal {ot ]\inQ, we le.arn that the construction of the 

 buildings uf the \"crkes Observatory is advancing rapidly, and it 

 is hoped the 40-inch refractor will be ready for use in Sep- 

 tember or October. The Observatory is situated on the shores of 

 Lake Geneva, Wisconsin, at an elevation of 180 feet above the 

 lake, and is about seventy-five miles from Chicago. The dome 

 for the great telescope, which is being built liy Warner and 

 Swasey, is 90 feet in diameter, with a shutter opening 12 feet : 

 the rising lloor is 75 feet in diameter, .and will have a vertical 

 movement of 22 feet. The motive power for turning the dome 

 and elevating the floor of the Observatory will be supplied by 

 electro-motors. 



In addition to the large telescope, provision is made for the 



NO. 1339, VOL. 52] 



use of the 12-inch telescope now at the Kenwood Observatory, 

 and another telescope of 16 inches aperture. The meridian 

 room is designed to accommodate a large meridian circle, but, 

 in the first instance, a transit instrument will be employed. 



The Observatory buildings appear to be designed on a very 

 liberal scale, and comprise offices, library, lecture theatre, 

 spectroscopic, physical, chemical, photographic, and other 

 laboratories. We understand that Prof. Barnard and Prof. Burn- 

 ham have accepted positions in the Observatory. 



The Granulation oi-- the Sun's Surface. — The granular 

 or mottled appearance of the surface of the sun is familiar 

 to all observers, and the great resemblance to terrestrial cirrus 

 clouds has long been recognised. A possible cause of this 

 appearance has been recently suggested by Dr. Scheiner (Astr. 

 Nach. 3279), the idea being that Helmholtz's investigations on 

 the formation of waves in our own atmosphere apply also in 

 the case of the sun. According to Helmholtz, air waves are 

 produced when two strata of air of different temperature and 

 density glide over each other ; if the lower layer is nearly 

 saturated with aqueous vapour, the wave crests will be centres 

 of condensation, in consequence of diminished pressure, and 

 will appear as clouds, while the depressions will form trans- 

 parent interspaces. On this theory a " mackerel sky " is pro- 

 duced when two series of waves cross each other. Dr. Scheiner 

 points out that somewhat similar conditions prevail in the sun ; 

 there are layers'of different temperature, and currents in various 

 directions in these layers, and in the photosphere the condens- 

 able gases are in an over-saturated state. He therefore con- 

 siders that the bright grains of the photosjihere are wave-crests 

 of two crossing systems of waves, rendered visible by an in- 

 crease of condensation. In the case of the sun, the observed 

 lengths of the waves — that is, the distance between the separate 

 grains — is from icxxi to 3000 kilometres, and it is believed that 

 waves of this magnitude might be produced without the 

 assumption of extraordinary velocities. 



Assuming this to be a true explanation, the photosphere must 

 be a very thin layer ; and since the granules are of about the 

 same size in all parts of the surface, the velocity of the currents 

 must be nearly equal in all heliocentric latitudes.' 



The S.'^tellites of Jupiter. — Not contented with his 

 brilliant discovery of a fifth satellite to Jupiter, Prof. Barnard 

 has been employing the great resources of the Lick telescope in 

 further investigations of the satellites which were discovered by 

 Galileo (Monthly Notices, R.A.S., vol. Iv. p. 332). One part 

 of his work has consisted of micrometric measurements of the 

 diameters of the satellites, and the results, reduced to a mean 

 distance of the planet from the sun equal to 5 '20, are as 

 follows : 



Angular diameter. DLimeter in 



„ miles. 



Satellite I. ... 1-048 ... 2452 



,, II. ... 0874 ... 2045 



„ IIL ... 1-521 ... 3558 



,, IV. ... 1-430 ... 3345 



It is pointed out that these values are in good accordance with 

 the mean values derived from nine sets of measures made by as 

 many different observers since 1829. Of the earlier estimations, 

 those made by Schroeter in 1 798 agree most closely with modern 

 results. 



Special attention appears to have been given by Prof. Barnard 

 to Satellite I., on which hediscovcrcd, with the 12-inch equatorial, 

 on September 8, iSgo, the existence of a bright equatorial belt 

 and dark polar caps. These appearances have been verified at 

 every favourable opportunity, and " they are, beyond question, 

 permanent features of the satellite, and will always be visible 

 when a favourable transit occurs." These markings on the 

 satellite fully account for all the phenomena which have been 

 reported of the distortion or elliiiticity of its disc, xs well as for 

 the apparent doubling of the satellite during some transits. 

 When the satellite is transiting over a dark part of the planet, 

 the white belt appears very prominently, while the dark poles 

 are c<irrespondingly difficult to see, so that, without very close 

 attention, the satellite looks like a thin white strip. If, on the 

 other hand, it be transiting across a bright part of the planet, 

 the white belt is losl in the bright l)ackgroimd, and the polar 

 regions appear ;is two separate dark spots, making the satellite 

 appear double. The dark polar caps are darkest at the poles, 

 and become rapidly less intense towards the equator. Prof. 

 Barnard considers that the phenomena observed on this satellite 

 indicate that its physical condition is similar to that of Jupiter. 



