1I have brought you from my home country, as a little present, a problem most worthy of that profound learning of yours. 2A spring rises in the mountain, runs down over the rocks, and is received in a little dining room made by hand; 2held back there for a while, it falls into Lake Larius. 2Its nature is remarkable: three times a day it rises and falls with fixed increases and decreases. 3This can be seen plainly and is observed with the greatest pleasure. 3You recline beside it and eat, and you even drink from the spring itself — for it is very cold; 3meanwhile at fixed and measured intervals it either withdraws or rises.
4A ring, or anything; 4else you place on the dry ground is gradually lapped by the water and at last covered, then is uncovered again and little by little left dry. 4If you watch longer, you may see both happen a second and a third time. 5Is it some hidden current of air that now opens, now closes the mouth and throat of the spring, according as it meets it when drawn in or has left it when expelled? 6This we see happen in flasks and other vessels of the same kind, which have no wide or immediately open outlet. 6For they too, although tilted and inclined downwards, check what they pour out in frequent gulps, as it were, through certain delays caused by the resisting air.
7Or does the spring too have the nature that the ocean has, and by the same principle by which the ocean is driven forward or sucked back, is this modest body of water by turns held back and discharged? 8Or, just as rivers that flow down to the sea are turned back by contrary winds and the opposing tide, is there something that drives back the outflow of this spring? 9Or is there a fixed amount of water in hidden channels, so that while it is collecting what it had drained off, the stream is smaller and slower; 9but when it has collected it, it flows out livelier and larger?
10Or is there some hidden and unseen balance, which, when it has been emptied, stirs up and draws out the spring; 10and when it is full, holds it back and chokes it? 11Do you investigate the causes — for you can — that produce so great a marvel: it is quite enough for me if I have described clearly enough what is produced. 11Farewell.