used now in an improved form on board ships of war.

The ordinary pump, or sucking-pump, as it ^vas at first called, though evidently known to the Greeks and Romans, and used in their ships, does not seem to have been much employed by them for domestic purposes. It was not till the fifteenth and sixteenth century that pumps became common and superseded the more ancient devices for raising water and even then the principle upon which the water was raised was little conceived of. The old doctrine of Aristotle, that nature abhorred a vacuum, was supposed to explain the whole matter, until one day a Florentine pump-maker having constructed a pump some 60 feet long, was astonished to find that he could not raise water in it more than 32 feet. As the Greek philosopher had^not assigned any limits to nature's abhorrence of a vacuum, it presented quite a problem, why in a pump it was found to be limited to a height of 32 feet. Torricelli, the disciple of Galileo, and after

him, Pascal, the author of the admirable lettres provenqales, which so victoriously expose the dangerous and insidious doctrines of the Jesuits, by the most beautiful and

PRELIMINARY ESSAY. 7

conclusive experiments, overthrew the long received notion of nature's abhorrence of a

vacuum, and demonstrated that the rising of water in the chamber of the pump, was produced by atmospheric pressure. As human beings were aggregated into larger societies, and the progress of civilization and refinement produced new and artificial wants, all the known modes of obtaining water from wells, springs, fountains and rivers, were found insufficient, and it became an object to devise some more compendious as well as abundant system of supply, and hence the resort to aqueducts.