The hydrants and valves used in connection with wood pipes in Philadelphia were made of metal, and it is presumed that the valves and hydrants used in other cities were likewise made of metal. [Illustration: Modern Vertical Triple-Expansion Pumping Engine] Only one brief century has passed since waterworks pumping stations were introduced in the United States, but what wonderful improvements have been made in pumping machinery design within that short space of time! Steel and iron have taken the place of wood in the manufacture of boilers and pumps, and instead of the leaky, unsatisfactory apparatus of other days, even when working under low pressures, we now have pumping engines which will work continuously month after month under several hundred pounds pressure, and deliver the daily volumes of from a few hundred to many million gallons of water. [Illustration: ·AQVEDVCT·CROSSING·THE·ALCANTARA·VALLEY· ·SPANISH-PORTVGESE-BORDER·] [Illustration: CHAPTER VII] SYNOPSIS OF CHAPTER. Early British Sewers—Sewer in the Great Hall of Westminster—Shape of Early English Sewers—Adoption or Recommendation of Pipe Sewers—Early Paris Sewers—Paris Sewers of To-day—Lack of Sewage Data in America—Effect of Memphis Epidemics on Sanitary Progress. The earliest mention we have of English sewers is contained in an old record of the fourteenth century, which informs us "The refuse from the king's kitchen had long run through the Great Hall in an open channel, to the serious injury to health and danger to life of those congregated at court. It was therefore ordered that a subterraneous conduit should be made to carry away the filth into the Thames." This description of the sewer from the Great Hall presents a vivid picture of the sewers of that day. At first the main sewers were natural water courses which, having become offensive, were arched over to shut out the sight and odor. Street gutters leading to those arched-over water courses became foul in turn, and were replaced by underground channels of the roughest brickwork or masonry. These drains which were square in cross section received and carried off slop water and rain water from the streets; the drains were constructed according to no regular design nor fixed principles, although usually they were 12 inches square and made by laying flat stones to form the bottom of the drain, then building walls of brick and topping off with flat stones, spanning from wall to wall. Excreta were collected in cesspools often built beneath the floor of the house. The introduction of the water closet about the commencement of the century, though it abated the nuisance of the latrine, aggravated the evils of the cesspool by introducing a large volume of water far exceeding in weight the actual excreta, waterlogging the subsoil. The difficulty and expense of emptying the cesspools were increased. Cesspools were therefore connected to sewers by house drains. The channels intended to carry off rain water became