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AT A TURE 



\Jan. 6, 1 88 1 



in South America, it is calculated that the cost of the observatory 

 would amount to 70,000 or 80,000 lire, of which 10,000 would be 

 for instruments, and the remainder wnuld provide three dwelling- 

 houses, salaries of four scientists, t^vo assistants, and two ser- 

 vants, food, &c. This is calculated for an absence of sixteen 

 months, twelve of which would be occupied in observations. 



The Geographical Society's Proceedings this month contains 

 three papers relating to Africa, the nrst of which is Sir Rartle 

 Frere's, on Temperate South Africa. This, as now printed, 

 embodies some u-eful statistical information and is illustrated by 

 a general map of South Africa. The other two piper> bring 

 some additions to our knowledge of the geography of West 

 Africa, Mr. Comber giving a short sketch of his recent journeys 

 in the interior of Congo, and Mr. Milum an account of his 

 travels in the Niger region. Thef.rmer is accompanied liy an 

 excellent map of the neighbourhood of San Salvador and of the 

 course of the River Congo from Sran'ey Pool to the sea. The 

 final report of the Executive Comnnttee of the African Explora- 

 tion Fund is published, together with a statement of receipts 

 and exj'enditure. In the Geographical Notes extracts are given 

 from a letter by Mr. Hoi-e of Ujiji, on the long-continued rise of 

 the waters of Lake Tanganyika, which he seems to onnect with 

 earthquake-movements. Mr. Hore is shortly about to return to 

 England, so that we shall probably hear more on this subject 

 before long. Among the other notes we may call attention to 

 these on the River Okavango, the survey of Eastern Pale-tiie, 

 and the United States' Survey operations in the neighbourhood 

 of Behring Strait. Increased attention, we note, is being paid 

 to the proceedings of foreign geographicil Societies, those of 

 the French Society being very fully reported. 



M. VossioN, who, it will be remembered, spent some time in 

 Burmah, and not long since read papers on that country before 

 the French Geographical Societies, has lately gone to Egy|jt to 

 take up the Vice-Consulship of Khartum. During his stay there 

 he is to pav special attention to the slave trade, and to the best 

 means of opening up commercial relations with the Sudan. 



Capt. Serra-Carracioli left Naples on November 23, iSSo, 

 for the Bay of Assab, having undertaken a mission, under the 

 auspices of the Club Africano, to inquire into the possibility of 

 developing commerce there and with the natives of the interior. 

 The Club Africano is desirous of establishing pearl, mother-of- 

 pearl, and sponge tisheries in the Bay of Assab. While funds 

 are being raised for more extensive operations, this expedition is 

 sent out to make a careful survey of the region, to form a depot 

 for further expeditions, whether commercial or scientific, and to 

 make other preparations. The expense is expected not to 

 exceed 600/. It is also stated that the Italian Geographical 

 Society have made arrangenents for the establishment of a 

 meteorological station at the Bay of Assab. The October part 

 of the DolUtino of the Italian Geographical Society contains a 

 long and valuable memoir by Signor C. de Amezaga on Assab. 



At the last meeting of the Lyons Geographical Society M. 

 Coillard gave an interesting account of his twenty years' experi- 

 ences ill South Africa. He was engaged for some time on a 

 missionary expedition in the Upper Zambesi region, and was 

 probably the means of saving Major Serpa Pinto's life, afterwards 

 accompanying him in some of his explorations. As no particulars 

 have yet been pu li hed of M. Coillard's geographical work in 

 this region, it is ui he hoped that his paper will be given in full 

 in the Lyons Socity's Bulletin. 



In last week's Missions Catholiqiies we have the concluding 

 insialment of some interesting and useful papers by the Bishop 

 ot Vancouver, en iiled " Uiie Vi ite Pastorale dans ie Territoire 

 d' Alaska." Per.- Montiton's notes .m the traditions and customs 

 of ihe Sandwich Islands are also c .ntinued. 



The January nu nber of Gooil Words contains the first of a 

 series of -paper by Mr. Jose,.h Thomson on his experiences 

 during his recent journey in East Central Africa. The present 

 instalment deals with the prei)ai at. .ry journey which he made 

 wih Mr Keith ohn-ton to Usain lara, and furnishes interesting 

 notes on the c.untry traversed. 



The Alexandria Correspondent of the Daily News tells us 

 that M, Chower, formerly a newspaper correspondent in Turkey, 

 Kurdistan, Armenia, and Albania, started on Deceinber 31, 

 "to explore Africa from north to south, from Alexandria to the 

 Cape of Good Hope." Bon voyage. 



The death is announced of Dr. Fr. Mook, the well-known 

 African traveller, who accompanied Dr. E. Riebeck on his 



expedition, which started in August last for the East. Dr. Mook 

 died at Jaffa shortly before Christmas. 



We have received parts 17 to 22 of the new edition of Stieler's 

 Hand-Atlas, with three supplementary parts containing in eight 

 sheets a very fine map of the Basin of the Mediterranean Sea. 



The Dutch Committee, which arranged the North Polar 

 Expeditions of the last few years, held a general meeting at the 

 Hague a short time ago, when the resolution was passed to collect 

 funds for the organisation of a fourth Arctic expedition. In the 

 meantime the Committee will endeavour to have a steamer built 

 for this purpose. 



ON HEAT CONDUCTION IN HIGHLY 

 RAREFIED AIR ■ 

 'THE transfer of heat across air of different densities has been 

 ■^ examined by various experim ntali-ts, the general result 

 being that heat conduction is almost independent of pressure. 

 Winkelmann (Fogg. Ann. 1875, 76), measured the velocity of 

 ccoling of a theraometer in a vessel filled with the gas to be 

 examined. The difficulty of these experiments lies in the circum- 

 stance that the cooling is caused not only by the conduction of 

 the gas which surrounds the cooling body, but that also the 

 currents of the gas and, above all, radiation play an important 

 part. Winkelmann eliminated the action of currents by altering 

 the pressure of the gas between 760 and i millim. (with decreasing 

 pressure the action of gas currents becomes less) ; and he obtained 

 data for eliminatirg the action of radiation tiy varying the dimen- 

 sions of the outer ves el. ITe found that, whereas a liwering of 

 the pressure from 760 to gi'4 millims. there was a change of 

 only I "4 per cent, in the value for the vel.icity of ciolingj on 

 further diminution of the pres-ure to 47 millims. there was a 

 further decrease of II per cent., and this decrease continued 

 when the pressure was further lowered to i'92 millim. 



About the same time Kundt and Warburg [Po^g. Ann. 1874, $) 

 can-ied out similar experiments, increasing the exhaustion to much 

 higher points, but without giving measurements of the pressure 

 below I millim. They inclosed a thermometer in a ylass bulb 

 connected with a mercury pump, and heated it to a higher tem- 

 perature than the highest point at which observations were to be 

 taken ; then left it to itself, and noted the time it took to fall 

 through a certain number of degrees. They found that between 

 10 millims. and i miUim. the time of cot ling from fio^ to 20° was 

 independent of the pressure; on the contrary, at 150 iirillims. 

 pressure the rate was one-and-a-half times as great as at 75° 

 millims. Many precautions were taken to secure accuracy, but 

 no measurements of higher exhaustions being given the results 

 lack quantitative value. 



It appears, therefore, that a thermometer cools slower in a so- 

 called vacuum than in air of atmosi-.heric pressure. In dense air 

 convection currents have a considerable share in the action, but 

 the law of cooling in vacua so high that we may neglect convec- 

 tion has not to my knowledge been determined. Some years ago 

 Prof. Stokes suggested to me to examine this point, but finding 

 that Kundt and Warburg were working in the same direction it 

 was not thought worth going over the same ground, and the 

 experiments were only tried up to a certain point, and then set 

 aside. The data which the.-e experiments would have given are 

 now required for the discussion of some results on the viscosity 

 of gases, which I hope to lay before the Society in the cou'se of 

 a few weeks ; I have therefore completed them so as to embody 

 the results m the form of a short paper. 



An accurate thermometer with pretty open scale was inclosed 

 in a ij inch glass globe, the bulb of the thermometer being in 

 the centre, and the stem being inclosed in the tube leading from 

 the glass globe to the pump. 



Experiments were tried in two ways : — 



I. The glass globe (at the various exhaustions) was immersed 

 in nearly boiling water, ar,d when the temperature was stationary 

 it was taken out, wiped dry, and all .wed to cool in the air, the 

 number of seconds occupied for each sink of 5° being no ed. 



II. The gl.jbe was first brought to a uniform temperature in a 

 vessel of water at 25°, and was then suddenly plunged into a 

 large vessel of water at 65°. The lulk of hot water was such 

 that the temperature remained seiisiidy the same during the con- 

 tinuance of each experiment. The number of seconds required 

 for the thermometer to rise from 25° to 50° was registered as in 

 the first case. 



■ Abstract of a Paper read before the Royal Society by William Crookes, 

 F.R.S., December 16, 1880. 



