192 REPORT OF THE RAIN GAUGES. 
sixth volume, new series, of the Society’s Me- 
moirs, and others which had been taken in similar 
localities, occasioned doubts as to the dependance 
which could be placed upon them as registering 
correctly the real amount of rain which reached 
the surface of the earth. 
Upon inquiry, it had been ascertained, that all 
the gauges of the Rochdale Canal Company were 
placed on the ridging of the roof, of the resi- 
dences of the lock-keepers, or other persons in 
whose custody they were; and in some instances 
the same plan had been adopted on the lines of 
the Ashton and Peak Forest canals. 
This position had, no doubt, been chosen under 
the impression that from its exposure, it must 
necessarily catch all the rain which fell, but it 
was probably not known at the time the gauges 
were placed, as it generally is now, that it is a 
fact, which has been ascertained beyond all ques- 
tion, that less rain is received by a gauge on the 
top of a house or a tower, than is received on the 
ground itself. Again, it had probably been over- 
looked, that the slope of the roof would operate 
in such a way, as considerably to interfere with 
the quiet fall of rain. If wind accompanied the 
