November 15, 1900] 



NATURE 



67 



W. p. Hiern's description of the dicotyledonous plants collected 

 by Dr. Welwitsch, the first having been published at the end of 

 1896. 



The Bibliotheca Geographica, edited by Dr. Otto Baschin for 

 the Berlin Geographical Society, is known to be a most com- 

 plete annual and international bibliography of geographical 

 literature. The sixth volume of this catalogue contains the 

 titles of papers published during 1897, classified into the usual 

 groups according to subjects, and with an authors' index. It is 

 thus possible to find, without the slightest difficulty, what papers 

 upon any particular district or branch of geography were pub- 

 lished in 1897, or to look up the list of publications of any writer 

 on geographical subjects. The volume contains 444 pages, and 

 it does credit to the editor and the society under whose auspices 

 it has been prepared. 



The additions to the Zoological Society's Gardens during the 

 past week include a Lioness (Felts led) from East Africa, pre- 

 sented by Major T. Soutar, Cameron Highlanders ; a Sooty 

 Mangabey ( Cercocebus fuliginosus, <J ) from West Africa, pre- 

 sented by Major G. McMicking, commanding C.I.V. Field 

 Battery ; two Ostriches {Strttthio camelus), a Nilotic Crocodile 

 [Crocodilus niloticus) from East Africa, presented by Mr. G. 

 Marsden ; an Egyptian Jerboi {Dlpiis oegyptms) from North 

 Africa, presented by Mrs. R. Gurney ; a Barn Owl {Strix 

 flammea), British, presented by Lady Hutt ; a Leopardine 

 Snake (Coluber leopardmus), a Tesselated Snake [Troptdonotus 

 iessellatits), European, presented by Mr. W. J. Wintle ; a Grey- 

 cheeked Mangabey ( Cercocebus albigena, <J ), a Sooty Mangabey 

 (Cercocebus fuligmosus, 9 ) from West Africa, a Moustache 

 Tamarin (Midas mystax) from the Upper Amazons, a Yellowish 

 Capuchin (Cebus flavescens) from South America, twj Tenrecs 

 { Centetes ecaudalus), a Short-nosed Tenrec (Ericulus setosus), 

 a Long-nosed Tenrec (Hemicentetes semispinosus) from Mada- 

 gascar, a Festive Amazon (Chrysotis festiva) from Guiana, two 

 Tui Parrakeets (Brotogerys tut), a Hawk-headed Parrot 

 (Deroptyus accipitrinus) from Brazil, deposited ; two Grey 

 Squirrels (Sciurus griseus, var. ) from North America, pur- 

 chased; a Bosch-bok (Tragelaphus sylvatictis, i), eight Mo- 

 cassin Snakes ( Tropidonoius fasciatus), born in the Gardens. 



OUR ASTRONOMICAL COLUMN. 



Observations of the Infra-red Spectrum of the 

 Solar Corona. — In a recent issue of the Comptes rendus (vol. 

 cxxxi. pp. 658-661), M. Deslandres describes some of his lattst 

 experiments in connection with the detection of the solar 

 corona at ordinary times without the intervention of an eclipse. 

 All the methods adopted prior to 1894 had been modifications of 

 spectroscopic examination, using either the visual or ultra-violet 

 rays, and were probably unsuccessful owing to the great proportion 

 of these radiations existing in our general sky illumination, thereby 

 diluting the small direct coronal light. In 1894 M. Deslandres 

 found evidence that the sky radiation was very poor in the infra- 

 red region, while the corona emitted this light abundantly, and 

 this has since been investigated by Prof. Hale, in 1895, without 

 producing any confirmatory results. M. Deslandres here suggests, 

 however, that this non-success may have been due to those ex- 

 periments having been made near the period of maximum sun- 

 spot activity, at which time the corona is much more uniformly 

 distributed round the limb than at periods of minimum. 



During the last eclipse, in May 1900, the author, in conjunc- 

 tion with M. Charbonneaux, found that the infra-red coronal 

 radiation was some one-half or one-third the radiation of the 

 same part of the sky after the eclipse, and the work has since 

 been continued daily at the Observatory of Meudon with the 

 same apparatus. This consists of a mirror 030 metre aperture 

 and I "50 metres focus, a slit spectroscope with crown lenses and 

 prisms, a sensitive Melloni or Rubens thermopile, and a very 

 sensitive Deprezd'Arsonval galvanometer. The slit of the 

 spectroscope was 12 mm. long and i mm. wide, (he prism train 

 being so arranged tli.it ilie thermopile only received the infra- 



NO. 1620, VOL. 63] 



red radiation from Ai" to Ai''-8. The slit has also been re- 

 placed by circular apertures o 4 mm. and i mm. diameter. 



The interesting conclusion is that, at all times of the day, the 

 sum of the deviations along the equatorial region has always 

 been greater than the corresponding sum of the readings in a 

 polar direction. As it is improbable that the diffuse heat of our 

 atmosphere would be unequally distributed over the small area 

 corresponding to the angular diameter of the sun, this difference 

 can only be attributed to the effect of the corona ; the present 

 time being a minumum of spots, the greater action along 

 the equatorial region is in agreement with the known con- 

 spicuous equatorial extensions of the coronal streamers and the 

 comparatively small polar plumes. Many variations in the dis- 

 position of the apparatus have been made to discover any 

 possible systematic errors, but the results have throughout 

 remained the same. 



In contrast with the above report should be considered the 

 preliminary statement of the results obtained by the expedition 

 organised by Prof. S. P. Langley from the Smithsonian Institution 

 during the same eclipse (Astrophysical Journal, vol. xii. pp. 69- 

 76). The light given from a 17 inch siderostat mirror passed to 

 a concave speculum 50 cm. diameter and i metre focus. 

 Arrangements were made whereby either the full image of a 

 part of the solar surroundings could be allowed to fall on the 

 bolometer strip, or the light previously passed through a prism, 

 thus sifting out any particular radiation for action on the bolo- 

 meter. 



Settings on the inner corona gave a distinct negative deflec- 

 tion with respect to the zero of the instrument, but this was 

 numerically less than the deflection given by a setting on the 

 centre of the dark moon ; this shows that the coronal radiations 

 were recognised by the bolometer, giving some 5 mm. deflection 

 greater than that of the dark moon. 



The fact of the negative deflection, however, indicates that 

 the radiation reflected by the earth's atmosphere during the 

 partial phase is vastly more intense than that of the corona. 

 Also " the corona is effectively cooler than the bolometer, and 

 appears, therefore, neither to reflect much light from the sun, 

 nor, chiefly by virtue of a high temperature, to give light of its 

 own, but seems rather to be giving light in a manner not asso- 

 ciated with a high temperature, or at least with the prepon- 

 derance of infrared rays usual in the spectra of hot bodies." 



Annual Report of the Melbourne Observatory. — In 

 the thirty-fourth annual report of the Melbourne Observatory, 

 Mr. P. Baracchi, the acting Government astronomer of Victoria, 

 summarises the work accomplished at the institution during the 

 period March i, 1899, to March 31, 1900. With the 8-inch 

 transit circle the total number of right ascension observations 

 was 331 1, and of north polar distance 2406. Of the latter, 1435 

 were on stars selected from the astrophotographic catalogue 

 plates, to serve as fundamental stars for the reduction of these 

 plates. 786 observations of heliometer stars were made at the 

 request of Dr. Gill, and have been sent to him for comparison. 

 The computations for the third Melbourne General Catalogue of 

 3100 stars are about two-thirds completed. The astrographic 

 work has made considerable progress, the two series of catalogue 

 plates and the series of chart plates with single exposure of one 

 hour having been completed with the exception of a few 

 scattered regions. Catalogue plates for regions above 80° of 

 declination are being duplicated, and the second series of chart 

 plates, with triple exposure of 30 minutes each, has been com- 

 menced, giving chree images of each star about 8" apart. The 

 measurements of the catalogue plates taken at this observatory 

 and the Sydney Observatory have been made at Melbourne, and 

 the progress made is stated in a joint report by Messrs. H. C. 

 Russell and P. Baracchi. The first twelve months of the 

 existence of the measuring bureau (commencing November, 1898) 

 were occupied in preliminary instrumental experiments and 

 training of observers, but during the last four months systematic 

 measurement has been carried on Several new micrometers 

 have been obtained, one by Repsold, similar to that u<ed by Dr. 

 Gill at the Cape. This has double slides, and thereby permits 

 quicker measurements. At present two observers, relieving each 

 other for alternate periods of one hour, measure in a day about 

 500 stars with the Repsold and ab->ut 400 with the local micro- 

 meter. As the total number of stars on the Sydney and Mel- 

 bourne plates is probably 1,500,000, it is e timated that with 

 three efificient measuring machines, and six observers employed 

 fiom six to seven hours daily, the whole may be accomplished in 

 some six or seven years. The photoheliograph, great telescope 



