174 



Stations. 



2 

 3 

 1 

 1 

 3 

 1 

 9 

 3 



Stations. 



1 

 3 

 1 

 3 

 1 

 2 



We could hardly have stronger evidence of the necessity for uniformity in 

 placing now gauges. Old gauges, however, must not be moved ; therefore it 

 is necessary to ascertain the correction for these various heights, and hence 

 the following Tables. But we have not yet hinted at the amount of the cor- 

 rection ; it will be presently shown that, within the above-quoted limits, viz. 

 from 4 inches above the ground to 16 feet 6 inches, the amount collected 

 will differ by 10 per cent. 



The gauges employed in the Calne elevation experiments were in num- 

 ber ten, in shape that known as " Glaisher's," 8 inches in diameter, and in 

 general features identical ; they were all constructed by Messrs. N^egretti 

 and Zambra, and remarkably accurate. They were placed at the following 

 heights : — Level with turf, 2 inches, 6 inches, 1 foot, 2 feet, 3 feet above 

 it: these were all exactly like fig. 1, the last two standing on dwarf 



Fig. 1. 



Fig. 2. 



■•'#?# 



|\ 



posts. Then there were gauges, like fig. 2, at 5 feet, 10 feet, and 20 feet 

 above the ground, supported on posts, into which a piece of gas tubing was 

 inserted (as lead in a cedar pencil), down which the water passed into 

 bottles at a conveniently accessible height. As objection may possibly be 

 taken to this aiTangement, on the ground of loss by evaporation, we may state 

 that it was not adopted imtil repeated experiments had proved that the loss 

 was almost inappreciable, even with delicate instruments. At 20 feet two 

 gauges were placed, one 8 inches and one 5 inches in diameter ; as it appears 

 that the diminution is not the same for 5-inch as for 8-inch gauges, we shall 

 not for the present discuss specially the observations with this gauge. During 

 the first four years the whole of the gauges were read daUy ; during 1867 



