Smithsonian Institution · Washington : Smithsonian Institution · leaf 188
46 ON THE CONSTRUCTION AND USE OF ts general arrangement is better comprehended from the sketch, Fig. 42, than from a labored description. Below, it runs on a pair of wheels a (one only is … The Observer’s Chair. visible) 9 inches in diameter, whose axles point to the centre of the circle upon which they run. They are prevented from shifting outwards by a wooden railroad b, b', and inwards by the paling /,/’. Above, the chair moves on a pair of small rollers c, which press against a…
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