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Again, in the development of the Vertebrata we have sundry examples of longitudinal integration. The coalescence of several segmental groups of bones to form the skull is one instance of it. It is further illustrated in the os coccygis, which results from the fusion of a number of caudal vertebræ. And in the consolidation of the sacral vertebræ of a bird it is also well exemplified.
Being of a segmental form, but with a projection at each extremity, which rendered their production and finish impossible by the ordinary lathe, I bethought me of applying what is termed the mangle motion to the rim of a face plate of the lay, with so many pins in it as to give the required course of segmental motion for the turning tool to operate upon, between the projections C C in the illustration.
The arched galleries cut during the excavations sometimes segmental, sometimes pointed, and often of a considerable height and width could never have stood in any other kind of earth without strong and numerous supports.
The arrangement of the ranging windows is quite conventional, but instead of marble lintels above them there are nicely gauged flat brick arches, while the basement windows are set in openings beneath segmental relieving arches with brick cores. The latter are reflected in effect by the recessed elliptical arches above all the windows in the walls of plastered rubble masonry.
The arrangement is such, that the fresh air enters, and is spread over the front of the diver's face, while the foul escapes at the back of his head. By a clever contrivance a segmental screw the helmet can be fixed to its neck with one-eighth of a turn, instead of having to be twisted round several times.
On each side cheek of the carriage is formed, by curved planing, a circular segmental race, opening inward or toward each other, rectangular in cross section and into each of which is fitted a segmental block just filling it up, and occupying a portion of its length so as to slide easily up or downward through the whole range of the arc or segment.
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