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the nature of things, as with Cicero on the art of rhe-toric. Many of our posterity will think that they are indiscourse with Yarro when they read his work on theLatin language : nor will there be wanting a number ofphilologers, who, consulting in various cases the Greekphilosophers, will imagine that they are actually talkingwith them. In short, the opinions of learned men whohave flourished in all periods, though absent in body,have greater weight in our councils and discussions thanwere they even present. Hence, O Caesar, relying onthese authorities, and using their judgment and opi-nions, I have written these books ; the first seven relatedto buildings, the eighth to the conduct of water, and inthis I propose treating on the rules of dialling, as de-ducible from the shadow produced by the rays of the sunfrom a gnomon, and I shall explain in what proportionsit is lengthened and shortened.

CHAPTER IY.

OF THE UNIVERSE AND THE PLANETS.

It is clearly by a divine and surprising arrangement,that the equinoctial gnomons are of different lengths inAthens, Alexandria, Rome, Piacenza, and in other partsof the earth. Hence the construction of dials varies ac-cording to the places in which they are to be erected;for from the size of the equinoctial shadow, are formedanalemmata, by means of which the shadows of gnomonsare adjusted to the situation of the place and the lineswhich mark the hours. By an analemma is meant a rulededuced from the sun’s course, and founded on observa-tion of the increase of the shadow from the winter sol-stice, by means of which, with mechanical operations