16 JOUKNAL OF THE ROYAL HOBT1CULTUHAL SOCIETY. 



When two-tenths of an inch of rain has passed into the receiver a 

 syphon comes into action, hy which the receiver is emptied and the pen 

 Drought back to the top of the paper to begin another descent. 



Almost the newest form of self-registering gauge is HalliweH's, in 

 which the trace is on a more open scale, and the action of the pen is 

 controlled in a very ingenious way. Here again the water passes into a 

 receiver, and in this case raises a float contained within it. As the 

 float rises it pushes upwards a pen, which moves freely between a couple 

 of guides, to keep it upright. At a given point in its rise the rod 

 attached to the float upsets a balanced hammer, which, falling upon a 

 small catch, liberates a syphon and allows it to fall into the receiver. 

 The syphon discharges the water in a couple of seconds or so into 

 another and lower chamber, from which it can run away somewhat less 

 quickly ; but before its escape has been accomplished the pen will have 

 fallen again to its zero, and another float in the second chamber will have 

 had time to lift the syphon back into its place, ready for its next liberation. 



Now let us turn to some of the results which have been obtained from 

 the systematic measurements of the fall of rain which have been made 

 in various places in the way I have just described, and first as regards 

 the British Islands. 



Rather more than forty years ago the late Mr. G. J. Symons, F.R.S., 

 began the "British Rainfall Organisation," which to-day consists of an 

 army of more than 4,200 observers, who daily record the fall of rain in all 

 parts of the kingdom, and forward their observations to Dr. H. R. Mill, 

 the present director of the Organisation, by whom they are collated and 

 arranged. Dr. Mill is thus able to supply us with information of the 

 most complete kind respecting the rainfall of the British Islands. 



The wettest parts of Great Britain and Ireland are the hilly districts of 

 our western coasts. The reason for this I have already referred to. It is 

 due to the uplifting of the moist air coming from the ocean into higher levels 

 by its encountering the hills in the west of Ireland, in Wales, the Lake 

 District, and the north-west of Scotland. The average fall of rain in 

 and around London is only about 24 inches per annum, but to the south 

 of London, on the hills of Surrey and Sussex, it amounts to 35 inches. 

 On the Devon and Cornwall moors it rises to 60 inches, and in North 

 Wales, the Lake region, and the Western Highlands of Scotland to 

 100 inches. 



To show the way in which the contour of a district may affect its 

 rainfall, take as an example a portion of Sussex of which Chichester is 

 roughly the centre, where the rainfall varies from 25 and 30 inches over 

 the lower part of the region bordering upon the coast to between 30 and 

 35 inches over the greater part of the Downs, and to between 35 and 

 40 inches in the neighbourhood of the highest and steepest summits. 



The difference between the rainfall in different years is sometimes 

 very large. The driest year of recent times was 1887, when all over the 

 kingdom there was a shortage of rain, and large areas had less than 

 20 inches in the year. 1903 was, on the contrary, the wettest year. 



Pride of place in the matter of heavy rainfall in Great Britain belongs 

 to Seathwaite, in Cumberland, where the daily fall has once at least 

 slightly exceeded 8 inches, and on several occasions has amounted to 



