the records of delivery most of this water is actually accounted for? For it is stated that 4,200 quinariae are delivered,[1] although elsewhere in the same records the amount taken in is put down as only 3,263. Besides this, I have discovered that not only 538 quinariae (the difference between our gauging and the recorded delivery) are stolen, but a far greater quantity. Whence it appears that the total found by me is none too large.[2] The explanation of this is, that the swifter current of water, coming as it does from a large and rapidly flowing river, increases the volume by its very velocity.[3]
I do not doubt that many will be surprised that according to our gaugings, the quantity of water was found to be much greater than that given in the imperial records.[4] The reason for this is to be found
- ↑ The 4,200 quinariae included the 103 given to Tepula. Cf. 68.
- ↑ Literally: "the amount estimated by me even exceeds (the figures which I gave)."
- ↑ "The most troublesome point of ignorance which Frontinus had to contend with was a total inability to measure the velocity of water, or even rightly and fully to grasp the idea of such velocity, whether as flowing in an open channel or in closed pipes. He accordingly compares streams of water merely by the area of their cross sections, and then worries himself into all sorts of explanations as to why his gaugings by areas, made irrespective of heads and velocities, do not balance. The frauds of the water-men, of the plumbers and of others who draw water unlawfully, always furnish a handy explanation, however." —Herschel.
- ↑ The following table will show how Frontinus arrived at the figures which he gives:—
Quinariae assigned to the various aqueducts in chapters 65–73: In records By measurement Delivery At intake At reservoir Elsewhere Appia 841 1,825 704 Old Annio 1,541 4,398 (2,362) 262 
1,348 
Marcia 2,162 4,690 (2,944) 95 [1]
1,840
Tepula 400 
190 
445 
92 
163 
Julia 649 1,206 (162) 803 [2] Virgo 652 2,504 2,504 Alsietina 392 [5] 392 (?) 392 Claudia 2,855 4,607 (3,312) 1,588 [3] New Anio 3,263 4,738 4,037 [4] 12,755 18,433 3,710 2,662 14,018 1 ↑ Besides 92 to Tepula. and 164 to Anio (cf. 67).
2 ↑ Besides 190 to Tepula (cf. 68).
3 ↑ Besides 162 to Julia (cf. 69).
4 ↑ Besides 163771 to Tepula.
5 ↑ Assumed from number delivered.
