. Appleton's dictionary of machines, mechanics, engine-work, and engineering. togovern the transmission of hydraulic power, unless the conditions be dictated by extraneous circumstan-ces, consists in passing the water over the summit of the wheel into the buckets in the mannerrepresented in Fig. 3774. This arrangement constitutes literally an overshot-wheel; but while wehave preserved tho name, it is no longer deemed necessary to apply it literally. In the present aeeeptation of the term, nothing more is implied than that the water is received into the buckets near thesummit of the wheel; and,
. Appleton's dictionary of machines, mechanics, engine-work, and engineering. togovern the transmission of hydraulic power, unless the conditions be dictated by extraneous circumstan-ces, consists in passing the water over the summit of the wheel into the buckets in the mannerrepresented in Fig. 3774. This arrangement constitutes literally an overshot-wheel; but while wehave preserved tho name, it is no longer deemed necessary to apply it literally. In the present aeeeptation of the term, nothing more is implied than that the water is received into the buckets near thesummit of the wheel; and, in ordinary practice, those wheels reckoned as overshot, by strict definitionVol. II.—54 850 WATER-WHEELS. come under the designation of high-breast wheels. One of the finest specimens of this construction yeterected is that represented in Figs. 3778 and 3779, in which the height of the fall bears to the diameterof the wheel the relation of 9 to 10. In the purely overshot-wheel this relation, as we shall immedi-ately have occasion to show, is very nearly inverted. In the construction of wheels of this class, the technical points which remain to be considered, after de-termining the diameter and breadth of the wheel from the height of fall and quantity of water furnishedby the stream, are the axle and its journals, the arms and their connections, the shrouding, sole, andbuckets. The subject of the axle and journals has already been very fully noticed when treating of shafts inthe article on Geering, (which see;) but it may be here added that in iron wheels of great weight andbreadth, in which the axle is consequently of corresponding diameter and length, and especially whenthe wheel is to be transported to a considerable distance from the work at which it is constructed, it isnot uncommon to make the axle of two, or even of three parts. When the axle is formed in this man-ner, the parts are fitted together by turning, and yre secured by bolts in strong flanges cast upo
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