in. THE SEVEN WELLS. THE COLN. 31 



stream was reduced by sinking into the open-jointed inferior oolite, 

 and holding 1 for some distance a subterranean course, a frequent 

 occurrence in the districts of the English oolites. 



The circumstances attending the flow of the water of the Seven 

 Wells were investigated by the late Mr. Simpson, C. E., for the 

 distance of twelve miles and a half from the source. The curious 

 result is expressed in the following Table ; the observations were 

 made in the dry autumn of 1 859 : 



cubic feet. 



Discharge from the spring head in one minute . . . .11 

 One-fourth of a mile down the stream . ... .31 



Three-fourths of a mile 61 



One mile ...... 73 



Two miles 105 



Two miles and a half . . . . . .165 



Four miles and three quarters 312 



Five and a half miles ' 320 



In this part of the valley lias clay is the stratum observed. At 

 this point the volume of the river began to decrease by rushing 

 into the oolites, and at 



cubic feet. 



Six miles and a half became 290 



Seven miles . 235 



Seven miles and three- eighths 179 



Eight miles and one-eighth I 1 ^ 



Eight miles and seven-eighths 45 



Nine miles and three-quarters 33 



Twelve miles and a half ........ 30 



Fourteen miles and a half 10 



Thus the stream was again found to be reduced to less than its 

 original current ; nor did it recover the loss in its onward course 

 to join the Thames at Cricklade, twenty-two miles from the source, 

 for it only delivered to the Thames no cubic feet in a minute. 



Below Cricklade the Thames flows eastward through a broad 

 valley in the Oxford clay, first receiving the little river Rey from 

 the chalk hills near Swindon, and then proceeding to Lechlade. 

 This town stands on a ' lingula ' or tongue of land on the north 

 side of the Thames, between the rivers Coin and Leach, which here 

 enter the main stream and bring supplies from the northern hills. 



The Coin. The Coin, a considerable stream, rises within five 



