42 
summer, the mean would agree very closely with the mean 
annual temperature of the rocks at some distance from the 
surface. On this account I shall take no notice of springs 
whose summer and winter temperatures differ more than 5° 
Fahrenheit, which removes a great number from our further 
consideration. Confining, then, our attention to those whose 
temperature does not vary more than 5°, we must expect to 
meet with some having the same mean annual temperature as 
the rocks at a moderate depth, which would correspond suffi- 
ciently closely with the mean annual temperature of the air 
at each locality, and also to find others having a somewhat 
higher temperature, either because they come from a very 
considerable depth, or on account of some other more local 
and special cause. 
Proceeding now to particular examples, I must say that 
the number of those which I have been able to observe in a 
satisfactory manner is more limited than I could wish, partly 
because so many of the springs have not a sufficiently uniform 
temperature, and partly from want of the requisite observa- 
tions ; for it is only at particular seasons of the year that they 
can be of value, and those are periods when I have seldom 
had the opportunity of studying the subject. Still, however, 
the number is I think sufficient to establish all the leading 
conclusions that we could expect to deduce. I may here 
remark that I have confined myself to springs situated quite 
in the country, so as to run no risk of their temperature 
being modified by artificial conditions, and that all might 
stand on the same footing, and be perfectly fit for comparison 
with each other. The thermometer employed was prepared 
for such purposes by Messrs. Nagretti and Zambra, and 
cannot, I believe, vary materially from the truth. I here 
subjoin a list which shows the locality of the spring ; the 
elevation of the locality, derived in most cases from the 
contoured six-inch-to-mile ordnance map of Yorkshire ; the 
