Page:The Kinematics of Machinery.djvu/625

 NOTES. 603

comes from the root schadf, which means to hang down to one side. This is very appropriate to the irrigating machine in question, because its lever, when not in action, always slopes downwards towards that side which is weighted with stone. The machine is not found in Syria, I have seen it only in Egypt." In the Descr. de VEgypte (xviii., 2, p. 539, et seq.} the shadoof is also called delu (delou) ; at the junctions of water channels from thirty to fifty shadoofs are not unfrequently to be seen together.

39 (P. 225.) Endeavours in this direction are even now to be met with among a few cultivated nations. Baron Von Korff saw, as he told me, in Egypt, a gunsmith who, while both hands were busy with his iron work, used his feet in working a saw to cut the wood for his gun-stock. The Tartars, both men and women, although engaged in their domestic duties, seldom lay aside their great curved embroidering frames. We need only look at the European stocking-knitter, too, to see the connection between these customs and our own.

40 . (P. 229.) A Spanish word, from the Arabic na-urah, so called from the snorting noise made by the emptying of the buckets : ndara, to snort (Heyse). Vitruvius also knew these wheels, which even in his time must have been of great antiquity (x. chap. v. [Vulgo x.]) :. . . " Circa eorum frontes affigun- tur pinnse, quse cum percutiuntur ab impetu fluminis, cogunt progredientes versari rotam, et ita modiolis aquam haurientes et in summum referentes sine operarum calcatura, ipsius fluminis impulsu versatse, prsestant quod opus est ad usum."

41 (P. 230.) A splendid example of this kind of machine stands in Zurich in the immediate neighbourhood of the Polytechnic School, a contrast which is humorous enough. It would be worth while to preserve at least drawings of this mammoth among machines, this doomed representative of a past epoch for the benefit of the coming race.

42 (P. 235.) [In the Patent Museum at South Kensington there are to be seen several wooden models of Watt's, of his proposed arrangements for obtaining rotary motion from the beam, as well as the sun-and-planet engine which for so long drove the machinery at his Soho factory. See also Note, p. 433.]

43 (P. 237.) It appears not to be well known, and may therefore be men- tioned here, that the Greeks were perfectly well acquainted with the pulley. The Eomans received both the thing itself and its name from the Greeks (cf . Vitruvius x. chap, ii., De machinis tractoriis). The three-sheaved tackle they called rpt'o-Traffroff, the five-sheaved Trej/rao-Traoros, the multi-sheaved generally TToAiWaoros. These names were certainly better than ours, for we have seen ( 43) that the characteristic part of the tackle is the stretched rope or cord, and not the revolving pulley or sheave. A mere fixed guide pulley the Greeks called apTf/j-ov.

44 (P. 237.) If we arrange the different forms of toothed wheels according to the increasing complexity of their theoretical treatment, we should have to adopt the order : spur-wheels, bevel -wheels, screw-wheels, hyperboloidal- wheels. It would, however, be a mistake to assume, without further inquiry, that this was the]' order of their natural development. As a matter of fact toothed wheels with crossed axes, and therefore with hyperboloidal axoids, appear to be the oldest, and to have led up to the conception of the simpler toothed wheels.

�