INVESTIGATION OF THE UPPER ATMOSPHERE 73 



Thus at Pyrton Hill and Manchester the second balloons sent up on 

 December 7 on the strength of a favourable forecast were both recovered 

 and furnished good records, and the second ascent from Manchester on 

 the 8th was equally successful. 



Altogether eighteen of the balloons sent up in this country were 

 recovered, and fifteen of these gave records to heights exceeding 10 km. 

 The results have not yet been discussed, but an inspection of them shows 

 at once interesting features. On the earlier days of the week these 

 islands were situated in a region of low atmospheric pressure in which 

 the gradients were small. All the records for this period showed that 

 the upper limit of the convective region of the atmosphere was reached 

 at heights between 7"5 and 8'5 km., i.e., very much below the average. 

 The conditions changed as a well-marked cyclone developed over Ice- 

 land, and the greater part of the area of the ascents lay in the limiting 

 region between this cyclone and an anticyclone whose centre was over 

 the North of Spain. The height of the upper limit mentioned above rose 

 simultaneously with this change to 12 km. or more at each station. It 

 fell again as a fresh cyclone from the Atlantic advanced over these 

 islands, and in the last ascent, made at Ditcham on the Saturday after- 

 noon while the centre of the cyclone was still west of Ireland, the height 

 had decreased to 10 km., which is about the average for that time of 

 the year. 



It had been hoped that the ascents would furnish sufficient results 

 to admit of a similar representation of the temperature conditions in 

 December to that for July shown a year ago by Dr. Shaw. The critical 

 ascents were those from Ireland, and unfortunately these were not a 

 success. Balloons which might have proved quite satisfactory in normal 

 July conditions turned out to be too weak for the weather prevailing at 

 Dhulough in the international week last December, and, instead of rising 

 with approximately uniform vertical velocity until they burst, they 

 developed leaks and on this account floated in the air probably long 

 enough to get clear of the land. Only two of the six sent up were 

 recovered, and these did not reach great heights. The results obtained 

 were : — 



Height Surface 05 10 1'5 2"0 25 30 km. 



T Dogree * A° \ 7,4 ° A-M- — 276 ° 27G ° 275 ° 273 ° 271 °" 5 269 °' 5 

 ° (_ Second balloon reached 1*5 km. only. 



The observations made with pilot-balloons in Barbados have been re- 

 ceived and are being dealt with by Mr. Cave. The heights to which the 

 balloons were observed range up to 5 km. 



The Committee find that a stronger balloon than that ordinarily used 

 can now be obtained at a slight additional cost, and they believe that by 

 using such balloons a successful series of ascents in Ireland may be 

 obtained even in winter conditions. They therefore recommend re- 

 appointment with a grant of 30Z. to carry out further experiments in 

 conjunction with the international ascents in 1910-U. 



