Lucretius, De Rerum Natura
William Ellery Leonard, Ed.

     Further, the water of wells is colder then
At summer time, because the earth by heat
Is rarefied, and sends abroad in air
Whatever seeds it peradventure have
Of its own fiery exhalations.
The more, then, the telluric ground is drained
Of heat, the colder grows the water hid
Within the earth. Further, when all the earth
Is by the cold compressed, and thus contracts
And, so to say, concretes, it happens, lo,
That by contracting it expresses then
Into the wells what heat it bears itself.
     'Tis said at Hammon's fane a fountain is,
In daylight cold and hot in time of night.
This fountain men be-wonder over-much,
And think that suddenly it seethes in heat
By intense sun, the subterranean, when
Night with her terrible murk hath cloaked the lands-
What's not true reasoning by a long remove:
I' faith when sun o'erhead, touching with beams
An open body of water, had no power
To render it hot upon its upper side,
Though his high light possess such burning glare,
How, then, can he, when under the gross earth,
Make water boil and glut with fiery heat?-
And, specially, since scarcely potent he
Through hedging walls of houses to inject
His exhalations hot, with ardent rays.
What, then's, the principle? Why, this, indeed:
The earth about that spring is porous more
Than elsewhere the telluric ground, and be
Many the seeds of fire hard by the water;
On this account, when night with dew-fraught shades
Hath whelmed the earth, anon the earth deep down
Grows chill, contracts; and thuswise squeezes out
Into the spring what seeds she holds of fire
(As one might squeeze with fist), which render hot
The touch and steam of the fluid. Next, when sun,
Up-risen, with his rays has split the soil
And rarefied the earth with waxing heat,
Again into their ancient abodes return
The seeds of fire, and all the Hot of water
Into the earth retires; and this is why
The fountain in the daylight gets so cold.
Besides, the water's wet is beat upon
By rays of sun, and, with the dawn, becomes
Rarer in texture under his pulsing blaze;
And, therefore, whatso seeds it holds of fire
It renders up, even as it renders oft
The frost that it contains within itself
And thaws its ice and looseneth the knots.