

Emanation in the Lower Regions ^of 'the Atmosphere. 25 



through the English Midlands and Yorkshire to Norway, 

 where it probably descended in the anticyclone situated 

 there on Feb. 27. 



Curves (2) and (3) of Map 3 give the possible trajectories 

 of the air arriving at Cambridge on Aug. 5, 7 a.m. The 

 wind at Cambridge was just S. of W. If on drawing ihe 

 trajectory a WSW. wind is taken, the path leads back by 

 curve (2) to a point on an anticyclonic ridge to the south of 

 Cornwall on Aug. 3, and it cannot be traced further. I£ 

 the wind is taken due W. the path leads back by curve (3) 

 to S. Wales, and then by strong northerly winds to Scotland. 

 It is quite doubtful from the working charts which path 

 should be tnken, but the emanation content would incline 

 one to the path from Scotland, although the existence of 

 uranium-radium-mines in Cornwall must not be forgotten. 



Curves (1), (2), and (3) of Map 4 give the trajectories of 

 the air arriving at Cambridge on May 10, 6 P.M , May 11, 

 6 p.m., May 12, 6 p.m. All the air had come from the 

 northern region, and from the paths of the trajectories one 

 would expect at first sight (1) to give a low emanation- 

 content, (2) a larger content, and (3) larger still ; the actual 

 results were just the reverse (see Table IV. A). The weather 

 phenomena over England were, however, anticyclonic on May 

 10th and cyclonic with freshening winds on May 11th and 

 12th. 



Map 5 gives three possible trajectories for the air arriving 

 at Cambridge on May 19, 7 A.m. The observers for the 

 Meteorological Office estimate the wind force on the Beaufort 

 scale, and their estimate is of its nature only very approximate. 

 A wind estimated as No. 3 on this scale may be anything 

 between 8 and 13 miles per hour with a mean value of 10 

 miles per hour. A wind estimated as No. 4 on the scale 

 may be anything between 13 and 18 miles per hour with a 

 mean of 15 miles per hour. It will be observed that the 

 minimum wind velocity according to one number on the 

 scale is the maximum wind velocity allowable for the next 

 lower scale-number. Thus there is a fair latitude allowed 

 for different observers; and probably some will always over- 

 estimate and some always underestimate. On Map 5 I have 

 plotted three trajectories corresponding to the maximum, 

 mean, and minimum values of wind force corresponding to 

 the numbers of the Beaufort scale. The pressure conditions 

 were anticyclonic on the continent on May 18 and 19, feebly 

 cyclonic over Britain, France, and Spain on May 16 and 17, 

 r and there was a persistent calm to the west of Ireland on 

 May 15 and 16, with prevailing northerly winds from Iceland 



