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tion of the lesser tympanum, the tongue enters Aqua- 
rius, all the holes fall perpendicular, and the flow of 
the water being thus lessened, it runs off more slowly; 
whence the vase receiving the water with less velocity, 
the length of the hours is increased. Thus, going 
gradually through the points of Aquarius and Pisces, 
as soon as the hole of the small tympanum touches the 
eighth part of Aries, the water flows more gently, and 
produces the equinoctial hours. From Aries, through 
the spaces of Taurus and Gemini, advancing to the 
upper points where the Crab is placed, the hole or tym 
panum touching it at its eighth division, and arriving at 
the summit, the power is lessened; and hence running 
more slowly, its stay is lengthened, and the solstitial 
hours are thereby formed. When it descends from 
Cancer, and passes through Leo and Virgo, returning 
to the point of the eighth part of Libra, its stay is 
shortened by degrees, and the hours diminished, till, 
arriving at the same point of Libra, it again indicates 
the equinoctial hours. The hole being lowered through 
the space of Scorpio and Sagittarius, in its revolution 
it returns to the eighth division of Capricornus, and, 
by the velocity of the water, the winter hours are pro- 
duced. To the best of my ability I have explained the 
construction and proportions of dials, so that they may 
be easily set up. It now remains for me to speak of 
machines, and the principles which govern them. These 
will be found in the following book, and will complete 
this Treatise on Architecture.