382 REPORTS ON THE STATE OF SCIENCE, ETC. 
Since the study of run-off involves questions of evaporation and per- 
colation, it would be desirable to set up evaporation tanks and percolation 
gauges in each area. The word ‘ desirable’ is employed because I think 
it would be well to encourage but impolitic to press water supply authorities 
and other participants to incur the expense of such installations, the value 
of which is problematical. I feel sure, however, that investigators would 
feel the need of some direct measurements—even rough measurements—of 
evaporation and percolation. In seeking the co-operation of authorities 
in any general scheme for Inland Water Survey, the desirability of installing 
evaporation tanks and percolation gauges, at least in a few of the more 
important areas, should therefore be borne in mind. 
II. THE ARRANGEMENTS NECESSARY FOR SUPPLYING THE DATA. 
The British Rainfall Organization has always relied for its information 
mainly on data contributed voluntarily by interested persons. Among 
these, authorities directly connected with water supply have always formed 
a very important section. I assume that it will be the policy of any 
organisation formed for the purpose of Inland Water Survey to follow the 
lead of the British Rainfall Organization in this respect. If that is done 
I have no doubt that the Survey Organisation will have no difficulty in 
obtaining the rainfall data that it needs without expenditure other than 
perhaps a few small annual payments to observers in remote and thinly 
populated areas. 
Except in so far as it will be necessary in some cases to improve the 
distribution of gauges over the catchment areas, it may be said that the 
means for supplying the rainfall data already exist in a fairly complete 
form. 'The need for more gauges in certain areas becomes very evident 
when it is recollected that in more than one recent water bill it has been 
necessary to make provision for the determination of the rainfall of the 
catchment area as a preliminary to the final assessment of compensation 
water. One of the first steps to be taken in any river basin where gauging 
“operations are contemplated is to go over the ground for the purpose of 
ensuring that such rain gauges as already exist are giving satisfactory results, 
and to arrange for starting such additional records as may be necessary 
to secure satisfactory evaluations of general rainfall. 
The gathering grounds under the control of existing water undertakings 
are, in the majority of cases, reasonably well furnished with rain gauges. 
Normally, therefore, it will be necessary to invoke the aid of private persons 
in extending the distribution of gauges into areas where the representation 
is unsatisfactory, and the fact has of course to be faced that the absence 
of human habitations makes it impossible in some areas to obtain readings 
through the usual channels. ‘The Meteorological Office has itself installed 
gauges in certain remote areas, e.g., in the region above Borrowdale in 
Cumberland, and at Newbridge and Cranmere Pool on Dartmoor, and 
arranged for a monthly visit to be paid to the gauges by a local resident. 
In some cases a small annual payment is made for such services. 
Whatever form the organisation for water survey may eventually assume, 
it is quite obvious that it will have to maintain a close liaison with the 
British Rainfall Organization. ‘The liaison should extend to all matters 
relating purely to rainfall and should include : ° 
(1) Advice by the British Rainfall Organization in regard to the selection 
of sites for new gauges and in regard to the reliability of records 
from existing gauges. 
