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Clacks — Tulular Valves—Nuremburg Engineers. [Book V.

Touched with the secret key, the doors unfold;

Self-closed behind her shut the valves of gold. a lliad, xiv.

It is probable that all valves were originally ln tbe form of doors ; thatis, mere flaps or clacks moving on a hinge, and either laying horizontallylike a" trap-door, inclined like some of our cellar doors, opening verticallyas an ordinary door, or suspended by hinges from the upper edge ; andsometimes they consisted of two leaves like folding doors. Examples ofall these are still common. Isis was represented by the ancient, Egyptianswith “ the key of the sluices of the Nile ” in her hand ; the instrument bywhich the doors or valves, like the locks in our canals were opened andclosed.

The most ancient musical wind Instruments known in the Eastern worldare provided with valves, as the primitive bag-pipes, and the Chinese Variation of this instrument, which Toreen describes as consisting of “ ahemisphere to which thirteen or fourteen pipes are applied, .and catchingthe air blown into it by valves.” The pastoral flute of Pan, from itsexpressing thirty-two parts, he supposes to have been of a similar con-struction. (Osbeck’s Yoyage, ii, 248.) Valves were of course employedin the Organs of Jubal, as well as in the bellows belonging to his celebratedbrother and other antediluvian blacksmiths. The ninth problem of theSpiritalia relates to valves. CöYiical metallic valves were used by Ctesi-bius in the construction of clepsydree. In most of the old representationsof pumps, flaps of leather, loaded and stiffened with pieces of wood orlead are figured. Agricola has given figures of no other. These clacks,as they are named, are in most cases preferable to the most perfect spheri-cal or conical valves of metal: the smallest particle of sand adhering to thesemakes them leak ; besides which, they are liable to stick. We have knownthem replaced with common clacks. Amontons , in experimenting witha forcing pump, found the valves, which were of highly polished metaland well fitted, adhere so strongly to their seats, that he had to Substituteleather clacks for them.

The spindle valve, or such as have a long shank to prevent their risingtoo high, and guiding them when descending, is said to be of French origin.

We have sometimes used a simple valve on the lower box of a pump.It consisted of a short pipe of thin and very soft leather secured to theupper side of the box. When the sucker was raised, the water rushedthrough this pipe, and when the stroke ceased, it was instantly collapsedby the pressure of the fluid above it, and then feil down on one side ofthe box.

Codes are a species of valve, but not self-acting like the latter. Inpumps and bellows the momentum of the entering fluids opens the valves,

* Doors opened and closed by secret machinery were formerly mach in vogue. Herontnade those of a temple thus to act. Vitruvius speaks of doors that closed by themselves,(and when opened, rose sufficiently high to elear the carpet.) In the old cities of Eu-rope, the gates were moved by concealed mechanism to prevent a surprise. Those atAugsburg were famous. A single person only could enter at a time, and he was inclosedbetween two gates tili the object of his visit was ascertained. As soon as he approachedthe first one, it opened of itself, he entered, “ and it closed upon his heels.” On reach-ing the second it acted in like manner. Düring these operations, the visitor saw noperson, although he was exposed to the scrutiny of officers within. The magistrates ofNuremburg , desiring to have a gate of the same kind for the Security of their city, sentsome engineers to take a mode!; but after several examinations, they returned homeand reported “ that withont pulling down the walls, and all the masonry, it was not inthe power of Beelzebub himself to find out how it was contrived, or to make one like itin a thousand years,”—(Blainville’s Travels, i, 250.)