VITRUVIU 
196 
be avoided are these: A lighted lamp is to be let down; and if it remain burning, you may 
descend without danger; but if it be extinguished by the strength of the vapour, then ad- 
joining the well, on the right and left, aestuaria are to be dug, that the vapour may be dissi¬ 
pated through the æstuaria, as through nostrils. When this has been done, and the water 
obtained, then the well may be encompassed with a wall, in such a manner as not to obstruct 
the spring. 
But if the place should be hard, or no spring should be found at the bottom, then by the 
means of signine work, the water from roofs, or high places, must be preserved. In signine 
works these rules are to be observed: first, the purest and roughest sand is to be provided; 
the cementum must be of flint stones broken, so as not to weigh more than a pound; and 
the lime must be the most ardent. It is so mixed in the pit, that five parts of sand may 
correspond to two of lime; the cementum is to be added in the pit: with this the walls of 
the well, as low as it is sunk, are, by the help of wooden levers armed with iron, to be 
plastered. The walls being plastered, the earth that may be in the middle is to be taken 
out quite to the bottom of the walls, and the ground being levelled, the pavement is to be 
laid with the same mortar, to the thickness intended. If these places be made duple, or 
triple, so that the water may be filtered in passing through them, it will be rendered more 
wholesome; for when the mud it may have subsides, the water becomes the clearer, and 
preserves its taste untainted: if this be not done, it will be necessary to add salt, in order to 
clarify it. 
Of the qualities and varieties of water, with its uses, and the means by which it may be 
conducted and examined, I have as well as I am able written in this book. The principles of 
dials and horologia I shall describe in the following. 
(8*) If these æestuaria were mere holes, the vapour 
posed of lime and the powder of tiles or bricks. At 
could as well be discharged through the mouth of the pit 
book 7. ch. 4. such a kind of mortar is mentioned by 
as through them; they might indeed hasten the evapora¬ 
Vitruvius, and directed to be used in damp situations: 
tion, but not so much as to be equivalent to the labour 
the words are arenato testa, which signifies a composition 
and time of digging the holes, or as could be done more 
of lime, sand, and powder of bricks or tiles. And at 
speedily by other means at the mouth of the well itself. 
b. 5. ch. 11. he says, that the seats in the xysti, which 
were open places, and consequently liable to be damp. 
(9*) Signinum is noticed at b. 2. ch. 4. where I have 
were formed of signinum. 
observed that I thought Galiani had misapprehended this 
The term signinum is supposed to be derived from 
paslage; but l must, in justice to Galiani, acknowledge that 
Signia, a town of Italy, where it may have been first used. 
1 was myself mistaken. 
or invented. 
Plny (35. 12.) speaking of Signinum, says it was com- 
END OF THE EIGHTH BOOK.