to its equability; and it is quite possible that in old times, when the necessary care and attention were bestowed, a tolerably uniform current of air and a fairly even quality of tone were obtained.
At any rate, a means of producing an absolutely equal pressure of wind, and one that could not possibly be disturbed by any inexpertness of the blower, was secured in the Hydraulic organ. This variety was invented by an Egyptian of the name of Ctesibius, who flourished in the third century b.c. The title is scarcely correct, since the instrument was 'hydraulic' only so far as the method of weighting the wind was concerned. It had not a single 'water-pipe' in it, and in all respects save that just mentioned was Pneumatic. The principle of the wind-regulating apparatus, which was both simple and ingenious, was as follows. Into a cistern made to almost any convenient shape, a vessel was placed, shaped somewhat like an inverted basin, supported upon wooden wedges about two inches from the bottom, and thus leaving an opening all round. This receptacle was the wind-receiver, and was nearly or quite immersed in water. Attached to the top of the receiver was a pipe (furnished with a valve below) through which air was forced by a wind-pump. When no wind was in the receiver, water would of course pass under its rim from without, and rise as high inside as outside, upon the well-known principle that water will always find its own level. When wind was passed into the receiver, the water previously within would be partially or entirely expelled, but would in its turn press its weight upon the air that had dislodged it, which would thus acquire the elastic force required to adapt it to its purpose. A second tube then conveyed away the air thus compressed, from the receiver to the pipes.
An organ thus supplied with wind could not be over-blown, because if more air were sent forward by the wind-pump than the receiver could hold, the surplus would pass under the rim of the receiver, and escape in bubbles from the surface. The general force of the wind could be increased by pouring more water into the tank, which added to its weight, and consequently to its pressure upon the air, or could be decreased by subtracting water from the previous quantity.
The Hydraulic organ occurs in the Talmud under the name of hirdaulis or ardablis; and a certain instrument is mentioned as having stood in the Temple of Jerusalem, which is called Magrephah, and had ten notes, with ten pipes to each note. This organ, however, was not a hydraulic one.
Great as may have been the theoretical merits of the Hydraulic system, yet in practice it does not seem to have supplanted the purely Pneumatic. This fact would imply, in the first place, that the defects of the Pneumatic system were not of so radical a nature as has generally been supposed; and in the second, that the Hydraulic system itself was by no means free from objections, one of which certainly would be that of causing damp in the instrument, an intruder towards whom organ-builders always entertain the greatest horror. The Hydraulic organ nevertheless continued in occasional use up to about the commencement of the 14th century, when it appears finally to have died out. Its weight and size seem to have originated a distinction between portable and stationary organs, which began early, and was perpetuated in the terms frequently used of 'Portative' and 'Positive.'
Although nothing very precise can be deduced from the ancient writers as to the time, place, or manner in which some of the progressive steps in the invention of the organ already detailed were made, yet it is certain that the germ of many of the most important parts of the instrument had been discovered before the commencement of the Christian era, the period at which we have now arrived.
During the first ten centuries but little appears to have been done to develop the organ in size, compass, or mechanism; in fact, no advances are known to have been made in the practice of music itself of a kind to call such improvements into existence. Yet a number of isolated records exist as to the materials used in the construction of the instrument; the great personages who exerted themselves about it; and its gradual introduction from Greece, where it is said to have taken its origin, into other countries, and into the church; and these have only to be brought together and placed in something approaching to chronological order, with a few connecting words here and there, to form an interesting and continuous narrative.
In the organ of Ctesibius, described by Hero, it appears that the lower extremity of each pipe was enclosed in a small shallow box, something like a domino box inverted, the sliding lid being downwards. Each lid had an orifice which, on the lid being pushed home, placed the hole in correspondence with the orifice of the pipe, and the pipe then sounded. When the sliding lid was drawn forward, it closed the orifice, and so silenced the pipe. With certain improvements as to detail, this action is in principle substantially the same as that shown in Figs. 3 and 4, and it continued in use up to the 11th century. But the most interesting part of this description is the reference to the existence of a simple kind of key-action which pushed in the lid on the key being pressed down, the lid being pulled back by a spring of elastic horn and a cord on the key being released. Claudian the poet, who flourished about a.d. 400, has in his poem 'De Consulatu F. Mallii Theodori' (316–19) left a passage describing an organist's performance upon an instrument of this kind, and also its effect, of which the following is a literal version: 'Let there be also one who by his light touch forcing out deep murmurs,