314 WATER STORAGE AND CANALIZATION. 
a recess of the opposite end of another block. The joints were 
secured by cement, and also by iron clamps run with lead. This 
aqueduct had a considerable depression in the centre, and appears 
to have been one of the first attempts to run water in an inv 
syphon, proving that the ancient Greeks had a thorough knowledge 
of the principle that water will rise to the level of its source. 
t land of genius, the birthplace of the mathematicians 
and engineers who revived hydraulic engineering in modern times, 
high appreciation of the arts and sciences. They appear to have 
been especially scrupulous as to the purity of their drinking-water 
and as to the cleanliness of their person. To ensure the first, they 
the Emperor Nero, Rome was supplied by no fewer than nine 
large conduits, having an aggregate length of 255 miles, W ch 
delivered over 173 million gallons daily. Afterwards this supply 
was increased to 3124 million gallons daily, equal to a rate of 
325 gallons to each inhabitant. The Aqua-Martia conduit which 
— supplied the drinking-water was 16 feet in diameter and 
sanitary measures to deliver a pure and ample supply 
of water to their different citi ually 
uragem: 
not made useful for the purpose of commerce and the taper a 
of troops and eesti Not content with thus developing the a 
resources of their own country, they studied, wherever ee oes 
led the way, to improve the condition of the vanquished . 
similar public works. They constructed a series of reser 
