340 ON ROMAN AQUEDUCTS. 



upon the general subject, "but there are one or two points con- 

 nected with it which admit of a kind of elucidation we have 

 hitherto perhaps not received. 



It was doubtful even in the time of Frontinus why a pipe 

 called quinaria, which, as is well known, is the fundamental 

 modulus of the whole system, had received that designation. 

 Setting aside the explanation, in itself improbable and resting 

 on no authority, that Agrippa had introduced a modulus equi- 

 valent to five of the original units, and therefore called quinaria, 

 two others remain ; the one that of Vitruvius, which Frontinus 

 mentions in connection with him, the other that which Frontinus 

 himself preferred. According to Vitruvius leaden pipes receive 

 their names from the number of fingers (digiti) which the sheet 

 they were formed of was in width. Thus a centenaria was 

 formed of a sheet of lead 100 inches in width, and so in all 

 other cases. Frontinus observes that one opinion touching the 

 origin of the word quinaria is, that it was introduced by the 

 plumbarii, and Yitruvius because it was a pipe made of lead 

 5 digiti in width; and we may remark that it is a way in which 

 a plumber would be likely to designate a particular pipe, inas- 

 much as it depends on the way of making it, and not on a 

 measurement to be taken after it is made. Frontinus goes on 

 to say that this is uncertain, meaning apparently the size of the 

 pipe so formed, for that in rolling up the lead the outside surface 

 was stretched and the inner one contracted. A modern writer 

 who has devoted much attention to Roman antiquities, without 

 being, so far as I have seen, happy in his conjectures in respect 

 to them, namely, Dureau de la Malle, mistranslates the text, 

 and makes Frontinus say that one part of the lead overlaps the 

 other ; the inference appears to be not Only that he mistook the 

 meaning of his author, but that he did not know how pipes were 

 made. At present of course pipes are made like wires, by ex- 

 tension, and I do not know whether the old plan is ever used ; 

 but comparatively speaking this is a modern improvement, and 

 in not very old books one may find described the process of 

 cutting the lead into strips, folding it up so as to bring the 

 edges together and then laying solder over the line of junction. 

 Frontinus's own account is that the name probably indicated 



