n science and mechanical skill.
The water is carried across this stream (which divides the cities of Washington and Georgetown) by means of two arches of cast-iron pipes of 3 feet 6 inches interior diameter, formed of sections with flanges firmly screwed to each other and braced; upon these are laid a bridge over which the street cars pass, and which serves as a public avenue of communication between the two cities.
The span is 200 feet, and the rise 20 feet.
The aqueduct which supplies Madrid with water, and has a large surplus for irrigation, is fed from the river Lozoya, where it emerges from the Guardarama Mountains.
This work was constructed under the superintendence of Don Lucio del Valle, between 1851 and 1858, and is 47 miles in length.
The river gorge is crossed by a cut-stone dam, 98 feet in hight, its wings abutting upon the solid rock of the hillsides.
The artificial lake thus formed contains 100,000,000 cubic feet of water.
The cost of the whole work was 57,897,36
screen with a hole cut through it was arranged at each end of the line, so that only one letter should be visible at a time.
The operator at the transmitting station waited until the letter be wanted came opposite the hole in the screen and then made the signal, causing the divergence of the pith-balls at the instant that the same letter became visible to the observer at the other station through the aperture in his screen.
Betancourt, in 1796, constructed a single-line telegraph between Madrid and Aranjuez, a distance of twenty-seven miles, in which the electricity was furnished by a battery of Leyden jars, and the reading effected by the divergence of pith-balls.
It was not, however, until the discoveries of Volta, Galvani, Oersted, Ampere, Faraday, and Henry elucidated the properties of electricity de- veloped by the voltaic battery, that a practical, continuously working instrument was feasible.
Following these discoveries came the practical instruments and codes of the no
id wood; likewise several moving figures, which beat time, etc.
We are told that the Emperor Theophilus, 829-41, had two great gilded organs, embellished with precious stones and golden trees, on which a variety of little birds sat and sung, the wind being conveyed to them by concealed tubes.
The Duke of Mantua had an organ in which the pipes and other parts were made of alabaster.
A pair of organs at Venice were made all of glass, and of the eight in the convent of the Escurial, near Madrid, one is said to be made of solid silver.
The devices required in order to make a pipe sound or speak are: the bellows, for supplying condensed air; a channel, for conducting it to the pipe; a valve or other contrivance, for admitting and cutting it off; and a lever, for opening and closing the valve.
The pipes are of two descriptions: the mouth or flute pipe (technically called flue-pipe) and the reed-pipe, which are each farther divided into several varieties.
Mouth-pipes, so cal
ceiving arm has a head of 180 feet; the length of the inverted siphon is 2 1/3 miles; its diameter 30 inches. It supplies the Spring Valley Mining and Canal Company, Cherokee Flat, Butte County, California.
The Bedonal siphon of the Madrid Aqueduct is an inverted siphon for crossing a valley, and is 4,600 feet in length.
It consists of 4 cast-iron pipes, each 3 feet in diameter, and laid parallel.
It forms one portion of the chain of works which brings the water of the river Lozoya to Madrid.
At the point where the river emerges from the Guadarama Mountains a cut stone dam 98 feet high is erected, its wings abutting against the rocks on each side of the ravine.
This artificial lake contains 100,000,000 cubic feet of water.
It was constructed under the supervision of Lucio del Valle, and is 47 miles in length.
The transverse section of the canal is about 20 square feet, and it discharges 6,600,000 cubic feet of water per day. Its cost was 57,897,368 francs, and it was built b