346 ON ROMAN AQUEDUCTS. 



it is called, through which it passes. If the side of a reservoir 

 be very thin the discharge is less than if it be thick, or if, which 

 comes to the same thing, a short horizontal tube is adjusted to 

 it. Now, at first sight, the Romans seem to have understood 

 this, for Frontinus states that a calix of not less than 12 digits 

 in length ought to be applied to the side of the reservoir. This 

 calix, he says, should be made of brass in order that its aperture 

 may not be tampered with ; but between the calix and the ad- 

 jutages of which we have been speaking there is the essential 

 distinction that the water escapes freely from the extremity of 

 the one, while from the other, I mean the calix, it passes at 

 once into the fistula. The Roman system of distribution is 

 essentially a system of distribution through pipes inserted into 

 the reservoir from which the erogation was made. To prevent 

 fraud the commencement of the pipe was made of brass, and 

 moreover, it was enacted, that for 50 feet the diameter of the 

 pipe should be the same as that of the calix to which it was 

 joined. It is one of Frontinus's complaints that the aquarii 

 would sometimes insert pipes without using a calix, and thereby 

 gave an opportunity, to use a homely phrase, of playing tricks 

 with the aperture of the orifice. There is nothing in this which 

 resembles an adjutage or short pipe through which the water is 

 allowed to flow freely; and it is, moreover, especially remarkable, 

 that although the Senatus Consultum would not allow the 

 grantee of the pipe to vary its size within 50 feet of the calix, it 

 is silent with respect to the direction in which it was carried, 

 though nothing can be clearer, that if the pipes slope downwards 

 the supply of water would be greater than if it were turned in 

 an upward direction, and of two persons who lived on different 

 levels one of them must have had an advantage over the other. 

 Of this, Frontinus appears to have been aware, as he states that 

 according to the relative position of the acceptorium and the 

 castellum, the erogation was to be burthened or relieved. But 

 according to what rule this correction was to be made, he has 

 not told us. 



The question of the nature of the calix is particularly worth 

 considering, because Prony's hypothesis for determining the 

 quantity of water brought by the aqueducts to Rome rests upon 

 an assumption that the calix was in the usual sense of the word 

 an adjutage. 



