256 REPORTS ON THE STATE OF SCIENCE, ETC. 



installation at the School of Agriculture at Cambridge was borne by Mr. C. S. Leaf 

 of Trinity College. The Committee is not yet in a position to report on the behaviour 

 of the instrument. 



At the meeting of the Association at Oxford in 1926 a grant of £70 was obtained 

 to aid in promoting the study of the relation of solar and terrestrial radiation by 

 making an apparatus designed by Mr. W. H. Dines generally available for that purpose. 

 The price quoted was contingent upon finding purchasers for a number of the instru- 

 ments to be made at the same time. The Committee, however, have found themselves 

 unable to apply for the grant made at Oxford, and there is no immediate prospect 

 of being able to utilise it in the way proposed. 



Investigations by Members of the Committee. 



The Committee is, however, of opinion that although organised co-operative work 

 had so far not been found practicable, the progress made by individual members 

 of the Committee was sufficiently encouraging for the endeavour to be continued. At 

 the suggestion of the Committee Mr. L.H. G. Dines has refurnished the Dines meteoro- 

 graph with a recording pen for humidity. The pamphlet of directions for observa- 

 tions at sea is now available, for ballons-sondes by the translation of the expose 

 technique of Teis3erenc de Bort and Rotch, and for pilot-balloons at sea by a special 

 issue of the Air Ministry. With the assistance of the Hydrographer, Commander 

 L. G. Garbett, Superintendent of Naval Meteorological Services, has secured a 

 considerable extension in the use of pilot-balloons at sea, and is still engaged upon 

 work with ballons-sondes. It is gratifying that H.M.S. Repulse, carrying the Prince 

 of Wales, and H.M.S. .Renown, carrying the Duke and Duchess of York, are enrolled 

 in the list of co-operators in the study of the upper air. 



The compilation of the observations of the upper air on the international days 

 of 1923, which is now completed as a specimen volume for the International Commission 

 for the Exploration of the Upper Air, is in itself a voluntary contribution of some 

 importance, especially as, by instruction of the International Commission for the 

 Exploration of the Upper Air, the compilation is expressed in units which bring 

 meteorology into line with other geophysical sciences as part of a common system. 

 The Committee has recorded its congratulations to the editors of the work on its 

 completion. 



Jn the specimen volume referred to is found the first general application of the 

 indicator-diagrams representing the results of observations of pressure and tem- 

 perature in the upper air by a curve referred to entropy and temperature as co-ordinates 

 and now known as tephigrams. They also form an important contribution to the 

 subject because they add materially to the effective expression of the thermodynamics 

 of the atmosphere. The Committee has watched their development through all 

 its stages. The introduction of the values of geopotential into the diagrams adds 

 materially to their interest. 



In other directions also there has been marked progress — the question of the 

 composition of the upper air was raised by a member of the Commission some years 

 ago ; upon his contribution was based a resolution of the Meteorological Section of 

 the U.G.G.I to invite the possessors of cryogenic apparatus to examine the atmosphere 

 from time to time to determine whether the hydrogen content was a fixed or variable 

 component. The question has been raised in a new way by the discussion of the 

 origin of the green auroral line and the conclusion of Prof. McLennan that a mixture 

 of nitrogen and oxygen extends far beyond the limit where they were supposed to 

 have been displaced by helium and hydrogen. 



Further light is also thrown upon the composition of the levels of the atmosphere 

 beyond the usual meteorological limit by the work of Prof. Lindernann and Dr. 

 G. M. B. Dobson on meteors and by Dr. Dobson's measurements of the amount of 

 ozone. 



Among other questions in relation to the upper air (in the meteorological sense) 

 which are of interest to members of the British Association, mention ought to be 

 made of the transmission of sound waves to distances so great as to require the 

 assistance of excessive refraction in the upper layers. Mr. Whipple was the first to 

 propound the idea that this ' abnormal ' propagation of sound to great distances 

 was to be explained by postulating a warm layer of air at a considerable height, 

 such as was required for the Lindeman-Dobson theory of meteors, but the layer would 

 have to be lower than those authors required, say at 40 instead of at 60 kilometres. 



