[155] Dederich reads “unciæ in popularibus rationibus adhuc observantur,” which seems better. The _uncia_ was an Italian, the _digitus_ a Greek measure. [156] It is evident from his making the square of the diameter ³⁄₁₄ greater than the area of the circle drawn upon the same diameter, that he takes the ratio of the area to the diameter as ¹¹⁄₁₄ to diameter 1. This is very near to the truth. The converse as given by him also agrees, as is seen by ¹¹⁄₁₄ + ³⁄₁₁ of ¹¹⁄₁₄ = 1. [157] Frontinus, c. 65. [158] It is of little consequence, but perhaps it may be interesting to know more accurately the result of the calculation. If we take 1.25 as the diameter of the quinary, and multiply the square of this by 0.7854 (the corrected ratio), we obtain the result in square digits, 1.22718. This multiplied by the 1825 gives 2239.6, that is, the result within one digit as given by Frontinus. [159] An Anglo-Roman company has now (1872) brought the Aqua Marcia (III.) again into Rome at so high a level, that it will supply cisterns at the tops of the houses. At present a number of ingenious contrivances are in use for sliding small buckets of water from the well or reservoir in the courtyard, to the upper windows and galleries round the central courts of the old houses or palaces. These reservoirs, whether large or small, are called _lacus_ by Frontinus and in the Regionary Catalogue. [160] The expression _reddita_ would imply that originally the Marcian had supplied the Aventine, and that, it having been superseded by the Claudian, it was now restored and used in addition to the other. See the extract—Frontinus, c. 76. [161] Frontinus, c. 89. [162] Ibid., c. 90, 91. [163] The division of the surface water from the sewerage, in the question of the drainage of large towns, is meeting with much favour, as it appeals to reason that what is good for the purposes of manure, is destructive to the healthy condition of the river, while the surface water, which finds its proper place in the river, interferes with the proper distribution of sewage. In Rome, there is frequently a small _specus_ or channel for pure water, contrived in the vault or upper part of the great _cloacæ_ or drains for the refuse water. Could not the same plan be adopted in London with advantage? But while this is canvassed, it seems singular that we hear little of the division of the _supply_, which, on the same principle, should certainly be divided. There are several towns so situated, that a fair supply of pure water might be brought very acceptable for drinking, but not in sufficient quantities to be applicable to other offices. The words of Frontinus are very concise and pointed:—