Spiral Wheels.
10. Spiral Wheels.
These in their principal construction differ but little from the foregoing: the following are the principal differences. The nave should be about seven inches long; instead of a spindle at top, make a hole for the case to be fixed in; in the nave must be fixed two sets of spokes near the top and bottom; the spokes should not be more than about three inches long; the cases must be placed in such a manner, that those at top play downwards, and those at bottom play upwards, but the third or fourth case must play horizontally. The case in the middle may begin with any of the others; six spokes will be sufficient for each set, by which the wheel may contain twelve cases, besides the top one: the cases should be about seven inches in length.