244 



NA TURE 



[July 13, 1905 



as great as that deduced from Planck's formula for this 

 case. In connection with similar work of his own, Mr. 

 Jeans {Phil. Mag., July) has just pointed out that 

 I have introduced a redundant factor 8 by counting 

 negative as well as positive values of my integers i, ij, (. 



I hasten to admit the justice of this correction. But 

 while the precise agreement of results in the case of very 

 long waves is satisfactory so far as it goes, it does not 

 satisfy the wish expressed in my former letter for a com- 

 parison of processes. In the application to waves that 

 are not long, there must be some limitation on the prin- 

 ciple of equi-partition. Is there any affinity in this respect 

 between the ideas of Prof. Planck and those of Mr. Jeans? 



Terling Place, Witham, July 7. Ravleigh. 



Proposed Observation of Mercury during the Solar 

 Eclipse. 



Dlring the eclipse of the sun on August 30 ne.xt there 

 will be an opportunity of making a very interesting 

 observation on the planet Mercury, to which I ask per- 

 mission to direct attention. 



.Mercury at the time of the eclipse will be very close 

 to the line joining the earth and sun — about 2° 54'- south 

 and 2° 54' preceding the sun — i.e. at an angular distance 

 from the sun's centre of nearly 4° 6'. Accordingly, the 

 illuminated part of Mercury will be an excessively thin 

 crescent which, if Mercury have an atmosphere, will have 

 its horns prolonged by atmospheric refraction. 



If a sufficiently skilled observer is provided with a 

 telescope upon which he can use a power of 200 without 

 loss of definition, and mounted — probably as an alt- 

 azimuth — so that it can be set beforehand upon Mercury, 

 the apparent size of Mercury will be that which would 

 be presented by a circle one-tenth of an inch across, 

 viewed with the naked eye from a distance of ten inches. 



This ought to be sufficient magnification to see whether 

 the horns of the crescent are prolonged, and, if so, it is 

 perhaps not impossible that the light would be sufficient 

 to enable a spectrum of the tips of the crescent to be 

 seen. 



If the whole of this programme can be carried out, we 

 should find out whether Mercury has an atmosphere, and 

 possibly learn something as to the constituents of the 

 atmosphere. G. Johnstone Stonev. 



30 Ledbury Road, W., July 10. 



The Planet Uranus. 



Astronomical amateurs will have an excellent oppor- 

 tunity of identifying Uranus on about July 16 next, for 

 the planet will be in conjunction with the star i Sagittarii 

 (mag. 53) on the night following that date. 



The position of Uranus at transit (loh. 30m.) will be • — 

 R.A. iSh. 5m. 58s., Dec. S. 23° 42' 21". 

 while that of the star will be (1905-5) : — 



R.A. iSh. 5m. 57s., Dec. S. 23° 43' 16", 

 so that the planet will pass about i minute of arc north 

 of the star. The latter may be easily picked up, as it 

 is nearly 4" .S. of the triple star fi or 13 Sagittarii 

 (mag. 4.1). 



Unfortunately, the objects will be low in altitude (15°), 

 and the moon happens to be full on the date of conjunction! 



On June 24 and July 8 I found Uranus a little fainter 

 than the star i Sagittarii. I have carefullv observed the 

 planet on several nights in a i2iin. Calver reflector, 

 powers 100 to 475. The disc appeared faint with a bluish 

 tinge, and no belts or other markings could be detected, 

 but the telescope is too small to deal effectively with an 

 object of this description. 



Bristol, July 9. W. p. Denning. 



The Exploration of the Atmosphere above the 

 Atlantic. 

 A PLAN for systematic work of this kind, which was pro- 

 posed by the writer in 1901 at the Glasgow meeting of the 

 British Association (Report, p. 724) after he had obtained 

 the first observations with kites flown from a Transatlantic 

 NO. 1863, VOL. 72] 



steamer, is now being partially realised. Last summer 

 Prof. Hergesell, on board the Prince of Monaco's steam- 

 yacht Princess Alice, executed sixteen kite-flights above 

 that part of the .Atlantic bounded by Spain, the Canaries 

 and the Azores, but without finding the expected south- 

 west anti-trade, although a height of nearly 15,000 feet was 

 reached (N.\ture, vol. Ixxi. p. 467). The present expedi- 

 tion, which will repeat Prof. Hergesell 's investigations 

 and continue them further south, is made possible through 

 the cooperation of our distinguished French colleague, 

 M. Teisserenc de Bort, whose steam-yacht Ottiria, of 

 350 tons, with a speed of 11 knots, and fully equipped for 

 aerial exploration, has just sailed from Gibraltar, and, at 

 the joint expense of her owner and the writer, will proceed 

 towards the equator by way of Madeira, Canary and Cape 

 N'erde Islands, making frequent soundings with kites 

 through the trade winds and equatorial calms. Bv means 

 of the self-recording instrutnents lifted by the kites, it is 

 expected that there will be ascertained the thermal and 

 hygrometric conditions of the various strata traversed, and 

 the depth and force of the trade wind in the different 

 latitudes. If the kites do not reach the south-west return 

 trade, which has been observed on the Peak of Tcneriffe, 

 the vertical range of observation may be increased b\ 

 liberating hydrogen balloons from Madeira and noting 

 their drift. 



Mr. Clayton, meteorologist of the Blue Hill Observ- 

 atory, left Boston on June 3 to join the Otaria at Gibraltar. 

 During his voyage to the ."Xzores on the White Star liner 

 Romanic he Revj kites, with instruments attached, almost 

 daily to the height of from five-eighths to three-quarters of 

 a mile, thus securing the highest observations in mid- 

 Atlantic, and it is interesting that this was done on June 7, 

 the day appointed for the international observations in the 

 upper air here at Blue Hill and in Europe. In general, 

 the temperature was found to decrease with altitude at 

 less than the adiabatic rate, and the relative humiditv to 

 decrease also, but in one ascent there was a rise of 

 temperature with altitude, preceding a change of wind 

 from west to south. A new form of folding kite was 

 employed, and it is encouraging to learn that the heights 

 attained were limited by the length and strength of the 

 wire on the hand-reel, which did not permit more than 

 one of these kites to be attached. On the two days when 

 no flights were made, a following wind became too light 

 on board the steamer to lift the kites, whereas, on the 

 yacht, this condition would have been obviated by simplv 

 lying-to, or steaming against the wind. 



While the cruise of the Otaria, which is to last onlv 

 six weeks, can hardly do more than elucidate certain 

 questions relating to the high atmosphere in the tropics, 

 it will demonstrate the possibilities and difficulties attend- 

 ing the extensive survey that the writer desires to under- 

 take, and which received the endorsement of the Inter- 

 national Meteorological Committee at Southport in 1903. 

 A. Lawrence Rotch. 



Blue Hill Meteorological Observatorv Hvde Park 

 .Mass., U.S.A., June 26. ' ' 



Ancient Antarctica. 



Prof. H. F. Osborn has said that the demonstration 

 of " the former existence of an .Antarctic continent 

 is one of the greatest triumphs of modern science." 

 But even if this be true, everyone must allow that 

 It occurred a very long time ago. This is proved 

 by the great diff'erences that exist between the floras 

 and faunas of the three great southern continents. 

 These differences are much greater than those between 

 the floras and faunas of North .America and Eurasia, 

 and consequently the land connections must have been 

 broken up in the south long before they were in the 

 north. We infer the former existence of an .Antarctic 

 continent from the existence of granite and foliated schists 

 in South Victoria Land, and evidence that it was formerlv 

 connected with northern lands is found in the existence 

 of flightless insects living there in the few patches of 

 mosses and lichens which manage to struggle through the 

 winter. These insects are not flightless through degener- 

 ation, but belong to an order which never possessed wings. 



