and Subterranean Water Storage. 75 



It will no doubt be said that even if the rainfall at Greenwich 

 has diminished durinf^ the last half-century, the result may be 

 due to purely local causes, and may perhaps not necessarily 

 involve a similar result in other parts 'of England. It may be 

 due to the immediate influence of the metropolis, for as far 

 as one can in any way estimate the result of the accumulation of 

 a large multitude of human beings within a limited area, and 

 the consumption by them or for them of enormous quantities of 

 fuel, the result might be to check the rainfall. The augmenta- 

 tion of temperature appears to be uniform throughout the country, 

 and not local, and this cause must certainly everywhere act in 

 the same direction, if not to the same extent, and if it have 

 any influence, tend to the general diminution of rainfall. 



It is much to be regretted that long series of observations on 

 rainfall made with trustworthy instruments can only be obtained 

 for a very small number of stations. This great need is now in 

 the way of being supplied. Commencing with 1850, there are 

 upwards of thirty stations in England, fifteen in Scotland, and 

 four in Ireland, in all of which good records are kept, but 

 the time is as vet somewhat too short to justify important 

 generalisations. The mean of the fifteen years, 1850-1864, is 

 certainly too low for all the stations, if we assume the absolute 

 mean to be that obtained from a long series of years. Still with 

 proper corrections these fifteen years are valuable for purposes of 

 comparison. For Greenwich the result thus obtained is 23*4 

 inches, or 7^ per cent, less than the mean. It does not, of 

 course, follow that this diminution is regular and uniform, or that 

 it is certain to continue, but as by referring to Diagram No. II. it 

 will be seen that during the last fifteen years at Greenwich there 

 occurred two of the largest rainfalls of any years within the fifty, 

 and that in other respects there were few extraordinary seasons, 

 except, perhaps, that of 1864, we may safely assume it to have 

 some foundation in fact. 



I have found extreme difficulty in obtaining reliable data on 

 which to base a definite proof of a gradual diminution of rain- 

 fall in various districts in England. The published reports of 

 the Registrar-General, although valuable and interesting, are 

 not absolutely continuous for the same places, nor is it always to 

 be known whether the rain-gauge used was to be depended on, 

 or whether it was situated near to or at some distance above the 

 ground. This is especially the case with the older observations. 

 Since 1848 the number of the stations has been increasing, but 

 till very recently there has been little harmony of observing, and 

 occasional interruptions in the record diminish the Aalue of the 

 lists. For purposes of comparison, however, the following dia- 

 gram (No. VI.), prepared from such records as exist will, I think. 



