The Origin of Screws and Gears.

Kaipara and Waitemata Echo, 7 August 1914, Page 8

The Origin of Screws and Gears.

Fremont, in his recent work on , the origin of 'screws and gears, brings out some interesting points on the subject. The 0 reeks are supposed to have invented the screw, but the two Roman authors. Pliny and Yitruvius, give the most ancient record we possess on the subject, although it must certainly have been known long before their time. Certain authors think that the idea of the screw comes from observation of a natural object of helical form such as a gasleropod mollusk, but Fremont thinks that it arises from forms in movement. For instance, when an edible snail is drawn out of its shell, we have j the idea of screw and nut. l"n- ---. fortunately the ancient records throw scarcely any light, on I lit* subject. The principle of the screw seems to have been hut little used until the middle ages, when it was .first applied for wine or cider presses. Muring the firs! centuries of our era. boll and nut was replaced by threadless bolts having a hole containing a conical pin, so that driving in the pin increased the pressure : such bolts and holes spaced along for adapting to different thicknesses of material. The Egyptian "noria" may. account for the origin of gearing. This seems to have been a wheel working on a horizontal shaft and operated by a crank, ;Mong the wheel surface were cleats for retaining the bucket chain which descended into the well, and in this way the buckets were raised, one after the other, full of water. But to drive the "noria" by an animal makes a vertical shaft ne-

cessary, and an ingenious person may have extended the cleats on one side in order to make them engage with a sort of lantern-shaped pinion placed on a vertical shaft.