86 NOTES ON MAJOR COAXES' DISCOVERY. 



at one end, into which the next pipe would fit, much as stone- 

 ware drainage pipes are made now. They were cemented to- 

 gether with a mixture of quicklime and oil. Ashes were mingled 

 with the water first sent through the pipes, these would settle in 

 any imperfect joint and stop leakage, which shows, by the way, 

 that there could have been no high pressure of water in these 

 pipes, and that they would be suitable for an aqueduct having a 

 very low gradient as the one at Dorchester undoubtedly had. 



The aqueduct was planned to a suitable fall ; if the ground 

 was impervious to water, the channel was cut in it, and was 

 carried round the sides of hill slopes, the fall being preserved ; 

 if hills intervened, a tunnel was cut through them ; the valleys 

 were either bridged, or the channel was carried at a suitable 

 height on the slopes of the hills round them (as at Dorchester), 

 " if," Virtruvius remarks, " the course would not be too 

 circuitous." Should the soil be gravel or earth, side walls were 

 to be built and an arch turned over the channel to protect the 

 water from the heat of the sun. In England this protection 

 would not have been needed. 



It is clear, therefore, that the aqueduct, presuming it to be so, 

 at Dorchester, has been constructed in its main features on the 

 Roman model. In one respect it differed from the Vitruvian 

 model. Vitruvius recommended that a fall of not less than one 

 in 200 should be given to the aqueduct, which would amount to 

 a total fall of 300 feet or more between Compton and Dor- 

 chester ; the actual difference in the levels between the two 

 extremities of the aqueduct fall very far short of that, and the 

 slightness of the decline, so much less than Virtruvius recom- 

 mended, might be urged as an argument against the theory that 

 the course was intended for an aqueduct. It might be urged that 

 on so low a gradient the water would be so long in flowing from 

 Compton to Dorchester that much of it would sink into the 

 ground and be lost, and that a very small quantity, if any, would 

 be delivered. Now, in reply to these objections, it should be 

 taken into account that the chalk which underlies these downs is 

 of a very close texture, so that there would be comparatively 



