Water-raising machines embodying the principles of the screw, stated by some authori ties as invented by Archimedes, the Greek geometrician and greatest mathematician of antiquity, and by others credited to the genius of Canon of Samos, a contemporary of Archi medes, about the year 242 s.c., are described by Vitruvius as of Egyptian origin, and were, according to other authentic records, employed in Egypt, for draining and irrigating land, many centuries before Archimedes visited that country. It consists of one or more flexible tubes of lead or leather, wound spirally around a solid cylinder of wood or iron, the ends of which are pivoted to supports, so that the whole arrangement may he revolved upon its axis, which is generally placed at an angle of 45 degrees to the horizontal. The lower end of the tube is placed below the surface of the water, and the upper end over a receiving trough at the desired elevation. When the machine is rotated the water entering the, lowest bend of the spiral is forced upward by each succeeding revolution into the other bends, and finally dis charged out of the uppermost into the trough. The Roman screws were made with plank grooves arranged spirally around a solid cyl inder, and the grooved cylinder thus con structed was fitted into and revolved within a hollow cylinder of the same length. Thus foreshadowing the turbine pump of the present day.
The connecting link between the various more or less elementary forms of water ele vators or *lifts)" already described, and the group of hydraulic machines designated as *dis placement pumps," is the modern chain pump, consisting of a tube through which the water is raised by a series of pallets or pistons. The pump of Ctesibius appears to have been of this character, although it consisted of only two single-acting pistons working in a cylinder, the water being raised by the up-stroke and ex pelled by the down-stroke, into a common re ceiving chamber. In this machine the atmos pheric pressure was not taken into considera tion, and its capabilities as a water-lifter re mained unrecognized until 1643, when Torri celli, the great Italian physicist, announced that water could be raised in a tube by the pressure of air. In 1641, Galileo, when consulted by a Florentine pump-maker, had failed to demon strate why water failed to rise in a closed tube above a height of 33 feet under the action of a suction pump. A year or two later, after the death of Galileo, Torricelli undertook the ex planation of that fact, his experiments finally resulting in establishing the law that the heights attained by liquids in a dosed tube, the upper end of which was a vacuum, under the pressure of the atmosphere, was proportional to their specific gravities. For example, under these conditions, the height of a column of mercury would be about 28 inches, while that of a column of water would be about 33 feet at the level of the sea. The direct result of
this experiment was the invention of the siphon barometer, in which the empty space above the column of mercury is known as the Torricellian vacuum; but the further experiments of Pas cal, a French mathematician and divine, in 1646, followed by those of Otto Guericke, a philos opher and mathematician of Magdeburg, Prus sia, and of Candido del Buono, a member of the Academie del Cimento of Florence, led to the invention of the *air pump,* an apparatus which is described under that title, and which must not be confounded with the atmospheric or displacement pump used for pumping water, which was not unknown to the ancients, and was probably used in some of its innumerable forms, long before the days of Ctesibius.
The expansive energy of compressed air, hot air and steam, was probably employed by the ancients as the motive power of pressure en gines to raise water many centuries before the Christian era. There are extant numerous au thentic descriptions of devices equipped with piston bellows, employed for this purpose by the ancient Egyptians, Hindus, Chinese, Peruvi ans and the Aztecs. Also descriptions of hot air devices and pressure machines operated by steam, the majority of which were contrived by the members of the ancient priesthoods. A great many of these machines are described in the (Spiritalia,) written by Heron, or Hero of Alexandria, a celebrated Egyptian mathemati cian and physicist, who lived in the 1st century A.D. The water-jet apparatus known as Herors Fountain, although asserted to have been in vented by him, was probably an old device at the time he described it. In either case, it is the oldest pressure engine ever described accu rately in which a volume of air was used in stead of a piston. In 1560 Baptista Porta, an Italian, published a work entitled 'Natural Magic," in which he described a method of pro ducing a vacuum by the condensation of steam, and its application to devices for raising water. Similar descriptions are given in the writings of Jerome Cardan, also an Italian,published some time between 1515 and 1570. Therefore, although nothing new was discovered by De cans, whose writings were published in Frank fort in 1615 and in Paris in 1624, or by Fludd, Worcester, Savery and Papin, whose investi gations and writings extended over the period from 1663 to 1698, the suggestions afforded by their experiments (subsequently elaborated by Freiburg in 1797 and Shone, Callon, Frizell and Pohl(( in the period extending from 1870 to 1900) have led to the development of the vari ous forms of modern air-lift pumps operated by compressed air and pulsometers operated by steam.