September 21, 1905] 



NATURE 



511 



by it, the principal object of these private conferences 

 of the directors of meteorological services was " the 

 discussion of concrete questions, the arrangements 

 of procedure as to methods of observation and calcu- 

 lation, and the organisation of common investi- 

 gations." Since that period several investigations 

 have been organised by the subcommittees nominated 

 by the international committee. 



The Munich conference nominated a committee for 

 cloud observations, under the presidency of Dr. 

 Hildebrandsson, whose duty it was to publish an 

 international cloud atlas, and to organise and direct 

 observations and measurements of clouds in different 

 countries during a year. The cloud atlas was pub- 

 lished in 1896 by MM. Hildebrandsson, Riggenbach, 

 and Teisserenc de Bort. International cloud observ- 

 ations and measurements were made at a great 

 number of stations from May i, 1896, to the end 

 of 1897, on a plan fixed by the committee at the 

 meeting at Upsala in 1894. The publications, in 

 accordance with instructions laid down by the sub- 

 committee, have appeared, and the principal results 

 have been published by Dr. Hildebrandsson in a re- 

 port of which the first part was presented to the 

 international committee at the Southport meeting, 

 and the second part is now presented to the con- 

 ference. The subcommittee has now completed its 

 work. 



At the Paris meeting, in 1896, other subcommittees 

 of a similar character were nominated, e.g. an 

 aeronautical committee, with Dr. Hergesell as presi- 

 dent, for the purpose of organising international 

 scientific aeronautical experiments, especially simul- 

 taneous balloon ascents at different stations. A 

 committee was formed under the presidency of Sir 

 Arthur Riicker for the purpose of international re- 

 searches on terrestrial magnetism and atmospheric 

 electricity. 



These subcommittees have had several meetings, 

 and have organised some important investigations. 

 A third subcommittee was constituted at Paris in 

 1896 for the study of solar radiation. There 

 have been no special meetings, but M. Violle has 

 presented to each sitting of the international com- 

 mittee a report of the principal researches undertaken 

 in different countries. At the St. Petersburg meet- 

 ing, in 1899, the international committee appointed 

 a telegraphic subcommittee, under the presidency of 

 Dr. Pernter, with the view of suggesting possible 

 improvements in telegrams for weather prediction. 

 Lastly, at the request of .Sir Norman Lockyer and 

 Dr. Shaw, the committee appointed a subcommittee 

 for the study of questions relating to simultaneous 

 solar and terrestrial changes, under the presidency of 

 Sir Norman Lockyer. 



The reports of these subcommittees show that their 

 labours have been of the greatest utility for the 

 development of meteorological science. By this 

 means it has been possible to organise and carry out 

 successfully investigations which would have been 

 Otherwise impracticable. It is very desirable that all 

 persons occupied with the same or analogous problems 

 should meet periodically, in order to fix ideas and 

 coordinate individual efforts, without in any way 

 restricting personal initiative. It may be asserted 

 with satisfaction, added Dr. Hildebrandsson, that the 

 meteorological conferences organised more than thirty 

 years ago have materially contributed to the develop- 

 ment of the science, to uniformity of views, and to 

 agreement between the services of different countries. 

 The constitution of the international committee con- 

 tributes effectively to the maintenance of good re- 

 lations, and promotes continuity in the labours of the 

 conferences. 



Dr. J. Hann was elected honorary president, and 



NO. 1873, VOL. 72] 



Dr. J. M. Pernter president, of the conference. In 

 the course of an address Dr. Hann said : — 



.As I am not the ollicial president, I shall take advantage 

 of my privilege of passing over in silence most of the 

 questions which form the programme of the present con- 

 ference, and I shall devote my attention to certain problems 

 of modern meteorology in which I have a special interest, 

 and the solution of which your discussions will assist. 



The use of balloons and kites has brought the explor- 

 ation of the upper regions of the atmosphere to a degree 

 of development of which we had no idea at the time of the 

 first international congresses at Leipzig and Vienna. Even 

 in 1879 the condition of the question had not changed, 

 when at the congress at Rome I was charged with 

 elaborating plans for observations in balloons and on 

 mountains. We had not then the apparatus for raising 

 kites, and had no idea of the important part they were 

 to play in meteorological science. It was reserved for 

 Messrs. Rotch and Clayton, of Blue Hill, to obtain the 

 excellent results with which we are all acquainted. 



Further, unmanned balloons were not invented, which 

 since, thanks to M. Teisserenc de Bort, have furnished 

 such surprising data relating to the temperature of the 

 upper regions of the atmosphere. The exploration of the 

 air by means of manned balloons was carried on without 

 any regular plan, and the observations obtained, as we 

 foun^ out later on, were unsuitable for scientific investi- 

 gations. It was only more recently, after the older ex- 

 periments by Welsh had been overlooked and forgotten, 

 that Dr. Assmann produced his aspiration-thermometer, 

 which is capable of giving accurate temperature observ- 

 ations during balloon ascents. 



Thus I was only able to recommend observations in 

 captive balloons. I directed attention to the superiority 

 of such observations over those made on mountain 

 summits, which were subject to the disturbing influence 

 of the ground, and gave a daily range of temperature 

 quite different from that observed in free air. 



But as observations in captive balloons were limited in 

 several respects, I also recommended that observations 

 should be made on mountains. Mountain observations, 

 although subject to local influences, are of great use ; they 

 give us information that observations made in balloons 

 or by means of kites cannot do, viz. the continuous 

 registration of meteorological elements (especially baro- 

 metric pressure) at a definite altitude, and are indispensable 

 in determining the conditions of the weather in the higher 

 regions of the atmosphere. 



I now come to another domain of research, which at 

 the present time has attained increased importance, viz. 

 the problem of weather periods and their connection and 

 dependance on the activity of the sun. This is one of 

 the grandest and most beautiful problems of modern 

 meteorology, for the solution of which astronomers, 

 physicists, and meteorologists must give mutual assistance. 

 One of the services which meteorologists can render in 

 furthering this important object is to obtain suitable 

 observations, by means of which the cyclical variations in 

 the atmosphere and their relations to solar activity may 

 be unequivocally determined. 



These observations must fulfil two principal conditions ; 

 they must be distributed as uniformly as possible over the 

 globe in order to give sufficient data relating to the con- 

 ditions of the atmosphere at fixed moments, and must 

 be suitable for closely following the variations in time of 

 these conditions during short as well as in very long 

 periods. The meteorological observations at fixed points 

 must give continuous and homogeneous series of mean 

 and extreme values. 



Unfortunately, the older observations do not always 

 satisfy these conditions. It often happened that the 

 principal meteorological observatories, while constantly 

 endeavouring to obtain more exact data, omitted at the 

 same time to take steps for obtaining comparisons between 

 the old and the new series of observations. This remark 

 applies above all to certain barometrical observations. 

 Thermometrical observations subject to local infiuences, as 

 well as barometrical observations affected by large or 

 unknown instrumental errors, may afford valuable means 

 for determining the variations of meteorological elements, 

 provided that the local influences and the corrections are 



