ON ROMAN AQUEDUCTS. 349 



was to be placed. In reply to these remarks, which of course 

 are not without weight, it is to be observed that the questions 

 with which Frontinus undertook to deal had not pressed them- 

 selves on the attention of any one at Rome until a comparatively 

 short time before. Several hundred years had no doubt elapsed 

 since the first aqueduct was constructed, but until concessions 

 were made to individuals, and further, until such concessions had 

 acquired sufficient importance to attract the attention of the 

 government, there was no occasion to attempt to determine how 

 much water any aqueduct brought, or how it was distributed 

 all went to public uses : private persons were only allowed to 

 appropriate what was afterwards called aqua caduca, that is, 

 water which would otherwise have run to waste ; and of this the 

 amount was probably insignificant. 



Not until the time of Agrippa, we are told by Frontinus, did 

 it become usual to make concessions of water, and he adds, that 

 it was not until after Agrippa's death that any attempt was 

 made to reduce these concessions to a system. Moreover, he has 

 particularly spoken of the substitution of a larger pipe in cases 

 in which a concession had been made of several quinarise, as of a 

 comparatively recent practice, and it is obvious that the diffi- 

 culties of the question could not be felt to their full extent, as 

 long as no other pipes than quinarias were employed as moduli. 

 We thus see that not much more than a hundred years, if so 

 much, can have elapsed during which any attention need have 

 been paid to the subject. At the end of this period, when Nerva 

 appointed Frontinus to the office of Curator Aquarum, every- 

 thing was, according to his own account, in the wildest con- 

 fusion. He blames the aquarii unsparingly, and no doubt they 

 had sins enough of their own to answer for ; but that there were 

 other vices in the system than the frauds with which he charges 

 them, appears sufficiently from his own statements. All his cal- 

 culations are completely at variance with the results which his 

 predecessors had obtained, and which were recorded in the Com- 

 mentarii Principum. He has no explanation to give of these 

 discrepancies. 



He seems to have been struck by finding that the amount of 

 water as estimated in quinariae and known to be distributed was 

 greater than the estimate of the amount supplied. With a strong 

 impression, therefore, that his predecessors had under-estimated 



