Evans — On Cavities in Old River Gravel, 447 



flint implements in connection with tliese cavities, it is to be ob- 

 served — 1st. That the evidence of such being the case is not sus- 

 ceptible of cross-examination, and moreover that one of the workmen 

 remarked to Mr. Fitch and me on what he regarded as a singular 

 fact, that no implements were found in these holes; and, 2ndly, 

 that if the pits were found in the proportion of 12 or 15 to an area 

 of a few score square yards, as has been stated, and implements were 

 found at all, it would be singular indeed if they were not found 

 either near or in the cavities, with which too the workmen would 

 naturally associate them. As a matter of fact, however, the imple- 

 ments do occur in other parts of the gravel than in or near the cavi- 

 ties, and some of those at Broom Hill have occurred in the lower 

 gravel with the calcareous matrix. 



It is, however, a priori improbable that such a gravel, a great part 

 of the constituents of which appears to have been derived from the 

 destruction of some river bluff, should contain so many relics of 

 human handiwork as gravels derived from the washing away of some 

 once-inhabited surface. 



If, however, it be true, as is generally believed and asserted, that 

 the flint implements occur in most abundance at the base of these 

 fluviatile gravels with a sandy nature, there is a reason why they 

 should be found not unfrequently in the pipes into which, of course 

 these lower beds of the gravel would be let down. I have known 

 instances at Thetford where the gravel has been extracted from pot- 

 holes running down into the Chalk, and in which implements have 

 been found at a considerable depth. The celebrated pit at Drucat, 

 in the valley of the Somme, affords another instance of implements 

 occurring in these pipes. 



Mr. Prestwich has already, in his valuable memoir communicated 

 to the Eoyal Society, suggested that these pipes may eventually afford 

 some means of estimating the antiquity of the beds in which they 

 occur. It is, however, extremely difficult to ascertain the exact 

 amount of carbonic acid which, on an average of years, the percolating 

 water of each year would contain. Could we, however, ascertain 

 the exact drainage area of one of these pipes, I think that some sort 

 of calculation might be made. For we know by experiment the 

 number of inches of rain which, with our present climate, percolate 

 annually to the springs in a Chalk district, while we also know the 

 quantity of chalk in solution held by each gallon of the spring water. 

 It must, however, be borne in mind that in all probability the 

 maximum quantity of carbonate of lime in solution is not attained 

 until after the water has percolated a considerable distance through 

 the Chalk. But without entering into any such calculation, I think 

 it must be evident that a cavity large enough ^' to hold a cart inside," 

 eroded by the carbonic acid of vegetable matter decaying on the 

 surface, and carried down by the rain, implies a lapse of time for its 

 erosion such as is quite in accordance with the antiquity which from 

 other considerations must be assigned to these beds, containing as 

 they do the undoubted handiwork of our barbaric forefathers. — 

 Eeprinted from the Norfolk News, August 25th, 18(58. 



