I
1
Let us enter then on an investigation of forms of water, and let us trace the causes that produce them; whether, as Ovid says:
There was a fountain silvery clear with gleaming wavelets; or, as Virgil says:
Whence through nine mouths with mighty roar of the mountain
The sea issues in broken waves, overspreading the fields with its resounding flood;
or, as I find it in your own poem, my dear Lucilius:
The stream of Elis wells up from Sicilian fountains.
2
3
Let us inquire by what method the waters are supplied; how it is that day and night unceasingly so many huge rivers roll down their course; why some are swollen by the rain of winter, some increase in summer when all the other streams fail. Meantime let us separate the Nile from the common crowd; it is a river of peculiar and unique character. We shall give it its turn by and by. At present we will confine our treatment to the common waters, cold as well as hot. In regard to the latter we must inquire whether the heat is due to natural or artificial causes. We shall discuss other waters too which are rendered remarkable by taste or some special virtue. Some, for example, I may explain, alleviate affections of the eyes, some, those of the sinews, some effect complete cure of chronic maladies given up by doctors as hopeless. Some again heal sores, some by being drunk ease internal pain and relieve complaints of the lungs and bowels. Some staunch the flow of blood; in fact their individual uses are as varied as their taste.