210 H. WAEEEJT — WATER-LEVELS NEAR ROTSTON. 



The levels, with one or two exceptions, were taken between the 

 30th of December, 1895, and 10th of January, 1896, at about 

 which time the winter rise of level usually commences in this area. 

 This is shown in the records given by Mr. Fordham in his papers 

 on the Barley and Odsey wells (see ' Transactions,' vol. v, p. 20 ; 

 vol. vi, p. 31). 



On the map will be seen the surface-contours, and I have also 

 attempted to show in dotted lines the subterranean contour of 

 saturation where it is 145 feet above Ordnance Datum, but it is 

 difficult to plot this with accuracy as the wells are in some cases 

 few and far between. The small circles on the map show the 

 position of the wells and springs in which levels have been taken. 



I have prepared four typical sections, showing the hydrostatic 

 gradients in this district. I do not think these need much comment 

 beyond a short description of their direction (shown on the map). 



Section No. 1 is taken through the line of springs which rise at 

 the base of the Chalk outcrop from Ashwell to Shepreth. It will 

 be seen that with the exception of the Upper Gatley Spring, 

 which is only about 3 ft. 9 ins. lower than that at Ashwell, there is 

 an almost unifonn gradient throughout. From Ashwell Spring 

 (145-9 ft. O.D.) to Shepreth Spring (71-8 ft. O.D.) there is a fall of 

 74 feet, giving an average gradient of nearly 5 feet per mile. 



Section No. 2 is taken higher up the escarpment nearly parallel 

 to the above, that is, in an E.N.E. direction, fi'om the " Hare and 

 Hounds" Inn near Odsey, through Koyston, to the "Coach and 

 Horses " Inn on the Newmarket Road. There appears to be 

 a slight depression imder Eoyston, but I do not think this is due to 

 any permanent lowering of the line of saturation by pumping. 



Section No. 3 is taken across the outcrop from Therfield Rectory 

 to Litlington Spring. The levels shown in this section were taken 

 on the 30th of March of this year, and must not be confused with 

 the others, which were all taken on the dates before mentioned. It 

 will be seen that the well at Therfield is actually over the ridge 

 separating the Cam and Lea basins. 



I had hoped to have got some levels in other wells near here, 

 in order to ascertain how nearly the underground parting-line 

 corresponds with the surface-ridge, but unfortunately I have been 

 unable to do so. I think, however, there is little doubt but that 

 this well does drain towards the Cam valley, as, the outlet being 

 comparatively near, there would be an easier passage for the water 

 in this direction than there would be towards the Lea valley. 



From Therfield Rectory (284-2 ft. O.D.) to Litlington Spring 

 (105-3ft. O.D.) there is a fall of 179 feet, giving an average gradient 

 of 45 feet per mile from the top of the ridge to the outlet spring 

 at the bottom. 



Section No. 4 is another cross-section from Therfield Rectory 

 through Royston and out at Melboum Spring. This gives a fall 

 of 177 feet and a gradient of 35|- feet per mile. 



The following is the list of wells, giving level at the surface, 

 ■VN'hich is generally the well-coping, the water-level, the level of 



