40 



NA TURE 



[Mav 11, 1893 



about three feet thick, they retain for a long time the heat which 

 they absorb during the day. The result is that there are layers 

 of air of different temperature in the room at night." To im- 

 prove fundamental astronomy, half a second of arc, he says, 

 must be seriously taken into account, and this can only be done 

 by employing a sound instrument and a properly-constructed 

 observing-room, " and we have neither the one nor the other at 

 the Cape nor at Greenwich. If we are going to fight for two- 

 tenths or three-tenths of a second, we must set to work de novo 

 with better instruments, better housed, for the determination of 

 constant error." 



The Lunar Atmosphere. — Various are the methods that 

 can be adopted for observing whether the moon has an atmo- 

 sphere or not, but some of them, such as those that depend on 

 solar eclipses, have been the least often attempted, since they are 

 of an extremely delicate nature. In eclipses, whether partial or 

 total, if the moon really had a moderately dense atmosphere, 

 we should be able, by photographing the sun when partially 

 covered by the moon, to note whether the delicate details on 

 the solar surface in the region of the lunar limb had suffered 

 any slight alterations in their forms. To note such variations 

 it is needless to say that photography must be em|>loyed, and 

 further that the photographs must be on a moderately large 

 scale, for if indeed there be changes of form they will by no 

 means be necessarily very apparent. For such observations as 

 these no better scale could be used than that adopted by M. 

 Janssen in those wonderful solar pictures that have done much 

 to help us in extending our knowledge of the sun's surface. In 

 fact M. Janssen, in Comptes Rendus for April 17 (No. 16) tells 

 us that in order to try this method again several plates were 

 exposed during the recent eclipse of the sun, but owing to the 

 state of the sky the conditions were not very favourable, as these 

 large photographs require a perfectly pure atmosphere. He 

 mentions at the end of his note that he has already made some 

 prepress towards the solution of this question from the photo- 

 graphs that were taken at Marseilles during the partial eclipse 

 of July, 1879. 



GEOGRAPHICAL NOTES. 



The Berlin Geographical Society has awarded the Humboldt 

 medal, the highest honour it can bestow, to Dr. John Murray, 

 editor of the Challenger reports, in recognition of the great ad- 

 vances in physical geography which are associated with his 

 „ame. 



The Paris Geographical Society has also awarded one of its 

 gold medals to a foreigner. Dr. Fridjof Nansen. Other gold 

 medals given by the Paris Society went to Captain Monteil, for 

 his great journey to Lake Chad, M. Dybowski, for exploration 

 on the Shari, and M. Lentheric for his monograph on the 

 Rhone. 



Mr. Gi;y Boothby has recently crossed Australia from north 

 to south. He started from Normanton on the Gulf of Carpen- 

 taria in March, 1892, travelled leisurely on horseback or in a 

 waggon to Bourke, and then descended the Darling in a boat, 

 and later a river-steamer to Morgan, thence by rail to Adelaide. 

 The journey occupied rather more than a year, and so far as ap- 

 pears little or no new country was traversed. 



The May number of the Scottish Geographical Magazine co^- 

 tains a paper on the people of the Lake Nyasa region, by Mr. 

 D. J. Rankin, in which he makes some serious charges against 

 Mr. H. H. Johnston, the British Commissioner. Mr. Rankin 

 considers the rule of the commissioner to be too severe, and finds 

 fault with his knowledge of the native tribes and their claims to 

 the land. 



Mr. E. A. Floyer has a long paper in the Geographical 

 Journal on the Eastern Desert of Egypt, illustrated by some 

 very characteristic pictures and a new map, the result of his 

 surveys. The expedition of which he was the leader was sent 

 out by the Egyptian Government in 1891, and surveyed 23,000 

 square miles of mountainous desert. The region is crossed by 

 a ridge of high ground in the higher peaks of which a few shep- 

 herds find a precarious pasture for their flocks, which feed on 

 the comparatively thick growth of acacias. The water-supply 

 is in the form of natural reservoirs of rain, in many cases con- 

 tained in limestone cavities which keep the wells supplied. 



NO 1228, VOL. 48] 



The Columbus file held in Paris on April 15, the 400th an- 

 niversary of the return of Columbus is reported at length in 

 the current number of the Revue de Geographic, the main fea- 

 ture being an address by M. Ludovic Drapeyron, who presided. 

 The novelty of such celebrations has passed, and it is difficult 

 to see how the celebration of the fourth centenary of each episode 

 of the life of Columbus after 1492 can be made serviceable to 

 geography or of special interest to the public. 



THE RECENT SOLAR ECLIPSE. 



■XXTE have already printed a number of telegrams relating to 

 observations of the solar eclipse of April 16 in various 

 parts of the world, and now reproduce from the Nottingham 

 Daily Guardian of May 9 an article on the work of the British 

 party in West Africa. This article is contributed by a special 

 correspondent of that journal, who writes from H.M.S. Blonde, 

 Las Palmas, April 28. It contains the first detailed information 

 which has appeared on the subject. The writer says : — 



The expedition left Liverpool on March 18 by the British and 

 African Company's steamer Jeneriffe, the company having most 

 generously contracted to convey them to the Gambia at greatly 

 reduced rates. Bathurst, near the mouth of the Gambia, was 

 reached on March 31, when the observers and their instrument! 

 were at once transferred to H.M.S. Alecto, which had beer 

 kindly placed at the disposal of the expedition by the Admiralty. 

 The Alecto, being specially designed for service on the West 

 African rivers, was eminently adapted to the purposes of the 

 observers, and, indeed, without some such aid the expedition 

 would have been impracticable. On the afternoon of April 2 

 the Alecto proceeded with the observers to the Salum River, 

 which lies some distance to the north of the Gambia, and Fun- 

 dium was reached on the following morning. The village, by 

 the way, is called Goundiougne by the French. The chief oc- 

 cupation in this part of Africa is the raising of ground nuts for 

 export. On arrival it was found that M. Deslandres and a small 

 staff from the Paris Observatory had already been at Fundium n 

 fortnight, and had got most of their instruments into position. 

 A neighbouring site, kindly offered to the British party by the 

 Administrator, was at once accepted as satisfying all require - 

 ments. It had the advantage of being partially enclosed, and 

 was quite near to one of the wharves, so that the instrument ; 

 could be put ashore without difficulty. The land around Fun- 

 dium is very flat, and a perfectly clear horizon was therefore 

 obtained. The site having been selected, plans for the arrange- 

 ment of the various instruments were at once drawn, and the 

 concrete bases were laid down, the necessary cement having; 

 been brought from Liverpool. Huts for the instruments, which 

 had likewise been brought from England, and the instruments 

 themselves were also erected with the least possible delay. , In 

 this preliminary work Lieutenant-Commander Lang and hi-; 

 staff, with the readiness characteristic of the British Navy, gave 

 the party all needful assistance. 



As eclipse work was new to all the observers, with the excep- 

 tion of Prof. Thorpe, who was in charge of the expedition, the 

 instrumental equipment was such as not to overtax any of them. 

 Prof. Thorpe, assisted by Mr. P. L. Gray, was in charge of a 

 6- inch equatorial telescope, belonging to Greenwich Observatory, 

 with the necessary accessories for determining the intensity of 

 the light at different points of the corona. The photometer 

 used was of the form in which the amount of light from a glow 

 lamp necessary to cause the disappearance of a grease spot on a 

 piece of paper was determined by measuring the strength of the 

 electric current which illuminates it. A number of such spots 

 were so arranged in the photometer that the image of the corona 

 formed by the telescope fell upon them, while on the other side 

 they were illuminated by a glow lamp, the whole, of course, 

 being inside a dark box. I myself, representing Prof. Norman 

 Lockyer, had the management of a 6-inch photographic 

 telescope, provided with a large prism in front of the object 

 glass for the purpose of determining the chemical constitution 

 of the corona and prominences. With this method of work a 

 separate image of each position of the corona or prominences is 

 obtained corresponding to each kind of light which it emits, and 

 this gives the clue to its chemical character. A duplex telescope 

 for photographing the surroundings of the eclipsed sun was in 

 charge of Sergeant J. Kearney, R.E., who has had the advan- 

 tage of a long and varied experience in photographic matters. 



