The principal thing is to have life on the very lips, ready to issue when summoned. This makes a man free, not by right of Roman citizenship, but by right of nature. He is the true freeman who has escaped from bondage to self. That slavery is constant, from it there is no deliverance; it presses us day and night alike, without pause, without respite. To be a slave to self is the most grievous kind 15 of slavery; yet its fetters may easily be struck off, if you will but cease to make large demands upon yourself, if you will cease to seek a personal reward for your services, and if you will set clearly before you your nature and your time of life, even though it be the bloom of youth; if you will say to yourself, Why do I rave, and pant, and sweat? Why do I ply the earth? why do I haunt the forum? Man needs but little, nor needs that little long. To this end it will be profitable for us to examine the nature of the universe. In the first place we shall rise above what is base; in the second, we shall set the spirit free from the body, imparting to it that courage and elevation of which it stands in need. Besides, subtlety of thought practised on the hidden mysteries of nature wil 16 prove no less efficacious in problems that lie more on the surface. And nothing is more on the surface than these salutary lessons we are taught as safeguards against the prevailing vice and madness--faults we all condemn, but do not abandon. I Let us enter then on an investigation of forms of water, and let us 1 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. 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; 2 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, 3 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.