Hilgendokf. — Artesian Wells in the Christchurch Area. 



155 



cannot be used to explain the rise of the well. This fact is emphasized 

 by the following graph (fig. 7), obtained in Invercargill in 1903 : it is 

 perhaps sufficiently striking to merit publication. 



Fig. 7. — Barogram showing Depressions due to Rise in Tempera- 

 ture at Noon. 



During a temporary absence from home I placed the barograph in a 

 window, so that an observer could read its records without entering the 

 house. The window happened to face north-north-west, and the sun fell 

 on the instrument just after midday. On each day the graph falls 

 nearly 0-25 in. as soon as the sun strikes the instrument, and it rises 

 again about 5 o'clock, when the sun passes off. The small fall of the 

 barometric pressure recorded for the evenings during the present obser- 

 vation is therefore not reliable, and cannot be used to explain the evening 

 rise of the well. 



No explanation of this phenomenon can, therefore, be offered as the 

 result of these observations. Mr. Speight has suggested to me that it 

 might possibly be correlated with the expansion of the earth by the 

 heating effect of the sun, and the passing of an earth- wave or earth- 

 heave towards the sun as it sets, as explained by Milne. No observa- 

 tions or calculations have been made to test the probability of this 

 suggestion. 



F. H. King (vide " The Soil," p. 162, &c.) found a morning rise in 

 his shallow wells, and this is explained by the fact that the soil- 

 temperature is highest in the morning, and that the expansion of the 

 soil-air expels some of the soil-water so that it reaches and raises the 

 water-table and thus the well. It is possible that observations might 

 show that at the outcrop of our water-bearing stratum the soil-tempera- 

 ture is higher in the evening, and this would explain the evening rise. 

 This is another of the numerous points on which no observations were 

 made. 



(2.) The Museum Well. 



This is a flowing well, 190 ft. deep, situated at the Canterbury Museum. 

 Christchurch. It is the deep well whose behaviour was recorded by 

 Captain Hutton (he. cit.), and Mr. Speight made further observations on 

 it during 1910 and 1911. I have worked up both Hutton's and Speight's 

 observations in the same way as I have my own, comparing them with 

 the barometer-readings, taking out weekly and monthly averages, &c, and 

 have found the following facts : (1.) The major fluctuations in the static 

 level of the well are small, the greatest annual variation recorded during 

 the two series of observations being 10^ in., as compared with 2 ft. 4 in. in 

 the Lincoln College well. (2.) Its level is changed by rain in the same 



