' jMav 20, 19C9J 



NA TURE 



;55 



Prof. Rolcli urged that all kite ascents should be tabu- 

 lated on a uniform plan, and that temperatures on the 

 ground-level should be given at intervals during the flight ; 

 he also spoke of the confusion that existed with regard to 

 the sign of the temperature gradient. 



Prof. Hergesell announced that a communication had 

 been received by Prof. Koppen, who was unable to attend 

 the congress ; he proposed that all measurements of atmo- 

 spheric pressure should in future be given in absolute 

 C.G.S. units. 



At the afternoon meeting on April 2 Prof. Bjerknes 

 read a paper on the theoretical applications of upper-air 

 observations, and spoke of the necessity for further co- 

 operation. He advocated a series of strictly simultaneous 

 ascents at all the stations, and suggested that on certain 

 days observations should be made at 7 a.m., i p.m., and 

 7 p.m. Greenwich mean time. At i p.m. ascents of 

 ballons sondes and kites should be made, and at the other 

 hours, besides the ordinary barometer and thermometer 

 readings at the ground-level, there should be as many 

 observations of pilot balloons as possible ; if possible, 

 ballons sondes might be sent up at the other hours, but 

 the mid-day ascent should be the principal one. He also 

 strongly supported Prof. Koppen 's proposition, and said 

 that the use of dynamical units for atmospheric pressure 

 ivould greatly facilitate theoretical work. M. Teisserenc 

 ce Bort said that he saw no difficulty in changing the 

 units if there were any real advantage to be gained by 

 'he change. Mr. Cave said that the practice had already 

 Deen introduced in England in the official publication of 

 the upper-air observations in the Weekly Weather Report, 

 and that Dr. Shaw was strongly in favour of the change 

 being generally made.' Prof. Bjerknes said that he would 

 publish tables to enable observers to change the old units 

 into the new ones. In regard to the series of simultaneous 

 observations advocated by Prof. Bjerknes, M. Teisserenc 

 de Bort proposed that one of the smaller series of ascents 

 should be set apart to be made on Prof. Bjerknes's plan, 

 and General Rykatcheff suggested that the time of the 

 ascents should remain as at present, but that they should 

 be made strictly simultaneously, and that additional pilot 

 balloon ascents should be made. 



M. de Massani then read a paper on the proposed upper- 

 air observations in Hungary, and Mr. Alexander one on the 

 instruction in aerodynamics in the United Services College, 

 Windsor. 



M. Teisserenc de Bort read a paper on the results of 

 theodolite observations on ballons sondes at Trappes, and 

 the importance of this method in the verification of heights 

 as determined by the barometer. As a result of his 

 observations, he finds that the cyclonic circulation of the 

 air in low-pressure systems does not extend to great 

 heights in the atmosphere, but that the balloon sooner or 

 later gets into a general wind current, mostly from west 

 to south-west in these latitudes ; over high-pressure areas 

 the wind is light, and great irregularities in direction are 

 found ; there are often several entirely different currents 

 superposed one above the other ; this condition had also 

 been observed in the tropics. With regard to the wind 

 in the stratosphere, M. Teisserenc de Bort has often found 

 a small change in direction at its lower limit, but the 

 changes are neither so regular nor so great as might have 

 been expected. In the discussion that followed Prof. 

 Hildebrandsson said that the observations of M. Teisserenc 

 de Bort in low-pressure areas confirmed his own observa- 

 tions of clouds ; it was clear that at 3000 metres or so 

 rhe isobars over a low-pressure area were no longer closed 

 on the polar side. Mr. Cave said that his observations 

 ■showed only a small change of direction when a balloon 

 ■entered the stratosphere, but there had generally been a 

 :onsiderable decrease of velocity ; his observations had 

 been made at times when the wind velocities in the lower 

 ■layers were considerably higher than in most of the cases 

 mentioned by M. Teisserenc de Bort. Prof. Hergesell 

 said that he had not found any regular change of wind 

 direction In the upper Inver, but he had in general found 

 a diminution of velocity ; but this diminution often occurred 

 at some distance above the lower limit of the stratosphere. 

 Prof. Hergesell gave an account of the experiments he 

 1 See introduction to the Weekly Weather Report, 1909. 

 NO. 2064, VOL. 80] 



had made to determine the rate of ascent of rubber balloons 

 in still air. From these experiments he has deduced a 

 formula from which, within certain limits, the rate of 

 ascent of a balloon may be calculated from its weight and 

 from its free lift when inflated with hydrogen. Both he and 

 M. Teisserenc de Bort consider that the vertical velocity is 

 constant up to moderate heights ; the theoretical increase 

 of velocity due to decreased density of the air is probably 

 more or less balanced by loss of gas from the balloon. 

 If we know the rate of ascent, and determine the heights 

 trigonometrically, we are able to measure vertical currents 

 in the atmosphere. From his own observations Prof. 

 Hergesell concludes that there is almost always some 

 vertical motion, and sometimes he has observed a vertical 

 current downward of as much as i metre per second, or 

 even more ; but in general a downward movement at one 

 time is more or less counterbalanced by an upward move- 

 ment at another, and therefore the one theodolite method, 

 when the height of the balloon is taken as a function of 

 the time, gives the wind velocities with very fair accuracy. 

 Some discussion ensued about the theodolites used for the 

 observations, and it was agreed that for accurate work 

 with a base line the theodolites should read to five minutes 

 of arc, but for the one theodolite method less accuracy 

 was needed. A triangular base with three observers was 

 also strongly recommended. 



M. Teisserenc de Bort read a paper on the theory of 

 the isothermal layer, which formed the subject of Mr. 

 Gold's recent theoretical investigations (Proceedings of the 

 Royal Society, vol. Ixxxii., 1909). Prof. Hergesell said 

 that he had not seen the original paper, but he thought 

 from the account that M. Teisserenc de Bort had given 

 that the theory had much to recommend it. M. Teisserenc 

 de Bort said he thought the adiabatic distribution of 

 temperature in the lower layers was due entirely to the 

 vertical circulation of air in this part of the atmosphere. 



On the afternoon of April 5 the Prince of Monaco was 

 present, and Prof. Berson gave an account (which has 

 appeared in Nature, April 8, p. 171) of his observations 

 on the Victoria Nyanza and off the east coast of Africa. 

 Prof. Palazzo gave an account, illustrated by numerous 

 lantern-slides, of his e.xpedition to Zanzibar and its neigh- 

 bourhood. 



At the meeting on Tuesday morning Prof. Hergesell 

 said that he had received a gift from the Kaiser to the 

 commission in the shape of two portable houses, which 

 could be used as a temporary observatory at any place 

 where an extended series of observations might be useful ; 

 it had been proposed to erect them for a year or two on 

 the Peak of Teneriffe, but the Spanish Government had 

 now decided to establish a permanent observatory there. 

 Colonel Vives y Vich gave an account of what it is pro- 

 posed to do, and said that kite and pilot-balloon ascents 

 would be made ; to hasten on the commencement of the 

 meteorological work, the Spanish Government would be 

 willing to accept the temporary loan of the houses under 

 certain conditions until the permanent buildings are ready. 

 It was resolved to send a telegram to the Kaiser thanking 

 him for his gift to the commission and for the interest 

 he had taken in the work, and one to the Spanish Govern- 

 ment accepting the conditions as to the houses. 



Dr. Assmann spoke of the importance of the study of 

 the upper air for aerial navigation, and thought that the 

 cooperation of aero clubs and others interested might be 

 obtained, and that by this means a wider study of the 

 subject might be possible. He looked forw-ard to the 

 establishment of more observatories where daily ascents 

 should be made as at Lindenberg, and hoped that in time 

 it might be possible to publish daily synoptic charts giving 

 tlie isobars at different heights above the surface. 



At the last meeting, in the afternoon , of April 6, the 

 following resolutions were carried : — 



(i) Prof. Koppen 's proposal to adopt absolute measures 

 for atmospheric pressure was referred to the International 

 Meteorological Committee. 



(2) The July series of observations to be made at 7 a.m. 

 Greenwich mean time, and pilot balloons to be sent up 

 three times a day in accordance with the proposals of 

 Prof. Bjerknes. 



(3) M. Vincent's proposal that frequent observations of 



