148 Transact/on*. 



Unfortunately, all the records did not begin at the beginning of the 

 year, those from Darfield not commencing till the 1st April, and those at 

 Rolleston till the 1st June. Valuable information was thereby lost. The 

 records are, however, complete and accurate for the periods they cover. 

 In the accompanying graph (fig. 5) the averages of all the readings of 

 the well for each week for five months are shown, and underneath them 

 the total weekly rainfalls for each of seven stations, Rolleston readings not 

 having been commenced. Zero for rainfall is made a sloping line, roughly 

 corresponding to the graph of the well, for the purpose of bringing the 

 rainfalls - graph near to that of the well, to facilitate comparison. To 

 simplify the figure, rainfalls are shown for only those weeks from which 

 conclusions may be drawn. The falls of Glenroy and Kirwee were identical 

 for the weeks shown, and therefore these two stations are represented by 

 only a single symbol — viz., dots and dashes. 



Starting with the station nearest the mountains — viz., Springfield — if 

 the rainfall at Springfield (squares) for the week ending the 15th January 

 was responsible for the rise of the well shown for the week ending the 

 22nd January, then also the much heavier rainfall for the week ending 

 the 26th February must have been responsible for the almost imperceptible 

 rise for the week ending the 5th March. These two results are inconsistent, 

 and therefore it may be stated that the rainfall on which the well depends 

 does not fall at Springfield, nor does the water-bearing stratum tapped by 

 the well outcrop there. Similar inconsistencies may be noted for other 

 localities, as follows : — Hororata : In the week ending the 15th January a 

 rainfall of 1 in. is followed by a rise in the well of 1-5 cm., and on the 23rd 

 April a rainfall of 1\ in. is followed by a decline of 1 cm. Glenroy shows 

 inconsistencies for the weeks ending the 15th January and the 23rd April ; 

 Darfield for the weeks ending the 2nd and the 23rd April ; Kirwee for 

 the weeks ending the 15th January and the 23rd April ; and Lawford for 

 the weeks ending the 15th January and the 23rd April. But when we 

 come to examine the rainfall at Lincoln, and compare that with the subse- 

 quent rises, or arrests of the decline of the graph of the well, a remarkable 

 degree of consistency is disclosed. The graph of the static level of the 

 well is as nearly parallel to that of the Lincoln rainfall as could possibly 

 be expected under the circumstances, and, being given the rise of the well 

 due to the rainfall of the 15th January, the graph of the one could be con- 

 structed with reasonable accuracy from that of the other. From this it 

 is evident that the stratum tapped by the well outcrops in a district with 

 a rainfall during the months shown almost exactly equal to that of Lincoln. 

 None of the stations recording for me shows such an equality, and so 

 it seems evident that the water-bearing stratum under consideration out- 

 crops nearer to Lincoln than to the nearest of the stations. That station 

 is Lawford, nine miles away, and so one would probably be safe in saying 

 that the stratum of shingle 341 ft. under the surface at Lincoln reaches the 

 surface seven miles or less up the plains. This would place the outcrop 

 somewhere about Rolleston- — a district noted for its loose shingly soil, 

 directly underlaid by coarse gravels, with no interposing layer of clay. 

 Such country is absorptive of water in the highest degree, and an ideal 

 catching-area for an underground water-supply. 



The surface of the land at Rolleston is 134 ft. above that at Lincoln. 

 The water-bearing stratum then rises 475 ft. in seven miles, or about 68 ft. 

 to the mile. The surface of the plains near their upper limit has a fall of 

 about 60 ft. to the mile, while between Rolleston and Lincoln it is onlv 



