154 Transactions. 



The evening rise is thus fairly well marked. During the months of 

 October and November I personally secured that all the wells in the 

 neighbourhood were running continuously, with the exception of one 

 (three-quarters of a mile away) which its owner was good enough to 

 shut off from 7 to 9 a.m. and 4 to 6 p.m. every day. The readings 

 during these two months were taken exactly at 8.30 a.m. and 5.30 p.m., 

 so that the well had an hour and a half to recover any disturbance 

 that might have been set up by the well whose flow was intermittent. 

 That this intermittently flowing well could have any effect on the 

 College well, so far, away, is questionable, and, in any case, it was not 

 (even during the months I did not keep special control of it) usually 

 running in the morning or usually shut off in the afternoon. The inter- 

 ference of neighbouring wells may therefore be rejected as a cause of the 

 evening rise. 



Any constant variations in temperature are similarly to be rejected. 

 I kept a record of the temperature of the flowing water just as it emerged 

 from the ground from the 10th to the 30th October. The temperature 

 varied from 12-81° C. to 12-90° C, and this variation was more probablv 

 due to the effect of the air on the stem of the thermometer than that 

 of the water on its bulb. In any case, the temperature never showed 

 any disposition to be regularly higher in the evening than in the 

 morning, and, if it had, a much greater rise of temperature would have 

 been needed to cause sufficient expansion of the water (inside an iron 

 pipe, on which the scale was carried) to account for the observed rise in 

 the static level. The water in the gauge-glass is, however, practically the 

 same water all the time, and therefore takes on to a considerable degree 

 the temperature of the atmosphere. It varied from 10-0° C. to 23-9° C. 

 during the month of October. The higher readings were, however, on 

 all but three occasions obtained in the morning, owing to the sun 

 shining on the gauge-glass and above-ground portion of the well-tube 

 in the morning and not in the evening ; indeed, the highest reading 

 (23-9° C.) was obtained in the morning, and on the same evening the 

 temperature was 12-0° C. In any case, an average evening rise of 

 temperature of about 25° C. would be needed to cause a 4 ft. column 

 of water (in a glass tube with an independent scale) to expand suffi- 

 ciently to accoimt for the observed rise in the static level. A shrinkage 

 of the wooden scale in the evening would also explain the rise ; but 

 means to detect and measure this, if it occurred, were not at hand, and 

 the fine of investigation held little promise. During the months of 

 October and November, also, records were kept of the barometric 

 pressure in the mornings and evenings, and it was found that the 

 readings were, on the average, lower in the evenings than the mornings. 

 The amount of the decrease in the barometric height in the evenings was 

 0-07 in., sufficient to account for a rise in the well of 0-56 cm., or more 

 than the actually observed rise. The barometric observations were, how- 

 ever, taken on an aneroid barograph, the mercurial barometer unfortu- 

 nately being out of repair. There is, I suppose, no question that the 

 temperature of a living-room is higher in the evenings than the morn- 

 ings, and I have rather good proof that increase of temperature de- 

 presses the record made by an aneroid barograph. The apparent fall of 

 the barometer each evening is, therefore, only a temperature effect, and 



