‹‹‹ Vitr. 9.0.17 | Table of Contents | Vitr. 9.1.1 ›››
18Hence, O Cæsar, relying on these authorities, and using their judgment and opinions, I have written these books; the first seven related to buildings, the eighth to the conduct of water, and in this I propose treating on the rules of dialling, as deducible from the shadow produced by the rays of the sun from a gnomon, and I shall explain in what proportions it is lengthened and shortened.
18Such, Caesar, are the authorities on whom I have depended, and applying their views and opinions I have written the present books, in the first seven treating of buildings and in the eighth of water. In this I shall set forth the rules for dialling, showing how they are found through the shadows cast by the gnomon from the sun’s rays in the firmament, and on what principles these shadows lengthen and shorten.