8 2 THE WATER SUPPLY OF ANCIENT DORCHESTER. 



ground, and no large reservoir could ever have been made 

 there. 



The fact of there being no trace of a large reservoir at the 

 head of the aqueduct, the comparatively large size of the channel, 

 and the insignificant volume of the stream, which rises at Comp- 

 ton Valence, and which in ordinary times is but a mere trickle, 

 drying up entirely before it reached the River Frome, points 

 conclusively to the aqueduct being intended to carry water from 

 the stream when in flood, either after rain or when water allowed 

 to accumulate in the small reservoir was discharged. This is all 

 the more probable, as the expensive puddling of the sides and 

 bottom necessary to make the aqueduct watertight, would not be 

 nearly so necessary as it would be if the aqueduct were required 

 to discharge a smaller continuous stream. 



Such an intermittent supply at the source involved a reservoir 

 at the Dorchester end, if a constant supply was given to the 

 town, even supposing the rainfall to have been much heavier 

 and more continuous in ancient times than it is now. My own 

 impression is that the depression now occupied by the public 

 gardens is the most likely spot. 



This spot is, I am told, on the site of the old ditch surround- 

 ing the town. Consequently if my surmise proves correct it 

 would show that the aqueduct was made in peaceful times, 

 when no danger was anticipated from tampering with the 

 defences. 



A reservoir in this position is high enough to have supplied 

 the greater part of the town by gravitation, so saving the 

 labour of carrying water from the level of the River Frome, 

 which is some 60 or 80 feet below the top of the town. 



To complete the survey satisfactorily, levels with the theodo- 

 lite ought to be taken from the last spot where the watercourse 

 is intact for several hundred yards beyond the last visible trace. 

 Such a survey would almost certainly show the true position of 

 the reservoir. 



I have not examined North Slip Plantation, but in all prob- 

 ability the remains of the aqueduct can be seen in it. 



