ON THE RAINFALL IN THE BRITISH ISLES. 177 



3. la cases of exiremehj heavy rain they collect water running along 

 the surface of the ground, and sometimes become filled, at others float away 

 on the water. 



4. They are more liable to accidental injury, and to collect all kinds of 

 rubbish than if slightly elevated. 



5. It is evident, from the Tables, that an error of 1 inch in the heiglit of 

 a gauge near the surface is of as much importance as an error of 1 foot at a 

 slight distance above it. 



Moreover, it must be remembered that up to the present time not half 

 a dozen pit-gauges liavc been used, and that therefore their adoption would 

 involve the correction of all observations hitherto made. 



And that though it appears probable that the rainfall actually reaching the 

 ground is nearly 5 per cent, greater than what has hitherto been supposed, it 

 would be precipitate to accept it without further examination. 



As nearly half the gauges in the country are now fixed, with their receiv- 

 ing surfaces, 1 foot above the ground, it would appear desirable that this 

 height sliould be generally adopted. 



In several previous Reports we have given the results of elaborate inves- 

 tigations of the percentage of rain falling in the various months in diff'erent 

 parts of the Eritish Isles ; these Tables uniformly referred to decennial periods, 

 such as 1810-19, 1820-29, 1830-39, 1840-49, 1850-59. We ha%-e there- 

 fore recently completed another decade, and one of which the returns are 

 much more complete than for any of its preciirsors. The computations of the 

 mean montlily and annual rainfall during this period are in progress, but 

 they are so heavy that they cannot be ready for this Report, and may per- 

 haps not be completed for the next. 



\Ve give in the Appendix the usual detailed Tables of monthly fall at 

 about 300 stations during the two years 1808-69, but we defer any remarks 

 iipon them until the averages are ready next year. 



Your Committee cannot close their Report without drawing attention to 

 the remarkable illustration of widespread interest in scientific pursuits 

 afforded by the fact that there are now nearly 2000 persons in the British 

 Isles regularly recording the fall of raiii, and carefully watching any depar- 

 ture from its normal distribution. Of the utility of this work, in a populous 

 and manufacturing country like ours, it is needless to speak ; but we may 

 mention that other nations and our own colonies are copying our system, 

 and that for water- works, canal, mill, and agricultural purposes rainfall 

 information is yearly more and more required. 



The services rendered by the observers are (with but a very few excep- 

 tions) entirely gratuitous, nay more, the observers themselves have to defray 

 the cost of printing the results of their labours. 



Considering that it is demonstrablj- a matter of national interest that this 

 organization should be made as permanent as possible, we cannot help thinking 

 tliat it would be a graceful and economical act were Government to ofter to 

 relieve the observers from the cost of reducing and printing their returns. 

 A few hundreds annually would probably suffice to hold together a body of 

 practised observers which Jias no equal in the world, and which, once broken 

 lip, could not be replaced ; since, irrespective of tlie difileulty of training 

 new observers, the continuity of the old observations would be destroyed. 



1870. K 



