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the height of the river were made with great care, readings being taken each 

 day to the nearest inch. On conipariosn with the graph of the static level 

 of the well no agreement could be observed in any case, and the perfect 

 indifference of the well to the flood on the 23rd March is typical of this. 



Another possible objection to the placing of the outcrop at Rolleston 

 is that this has been done almost entirely on the slight rainfall at Lincoln 

 and the heavier rainfall at all other stations for the week ending the 

 23rd April. This is quite true ; but occasions on which the rainfall is 

 markedly different at different points on the plains are rare, and some 

 years of observations may be needed to secure a confirmation, by this 

 method, of the conclusion drawn. In the meantime, the accuracy of the 

 rainfall recorded at the various up-plain stations is sufficiently substantiated 

 by their mutual agreement, and the accuracy of the record at Lincoln by 

 comparison with that made by three other observers in the neighbour- 

 hood. 



The Daily Fluctuation. 



Even during long periods of steady decline or rise of the well its static 

 level showed comparatively large daily variations. On some occasions it 

 would rise 3 in. in twenty-four hours (without rain), and would fall by 

 the same or a greater amount by the succeeding morning. Variations of 

 2 in. on successive mornings were common, and usually the morning read- 

 ings showed variations of over 1 in. The irregularities of the static level 

 within short periods of time during which no rain fell led to an attempt to 

 correlate the variations in the well with those of the barometric pressure 

 of the air. At length it was found that by turning the barometer-readings 

 upside down and multiplying them by four a marked degree of harmony 

 between the graph of the well and that of the barometer was displayed — a 

 harmony so consistent as to establish the fact that the level of the water 

 in the well and that of the mercury in the barometer are influenced by the 

 same causes. The accompanying graph (fig. 6) shows this clearly. 



Fig. 6.— Daily Readings of Well, Barometer, and Rainfall at Lincoln. 



