er. On the latter lever is a segment bring a full course of light with as little heat as possi- with segmental slot engaged by a bolt on the slide, so ble to the object to be exhibited. The distinguishing | chain may be operated by the treadle to propel the that when the nut of the bolt is loosened… … one floor only of a building, and which may be readily moved to various posi- tions, enabling articles at different ele- application of an achromatic negative lens to convert vations to be reached, has been patented by Mr. Robert the converging rays coming through the condensing W. Parmenter, of…
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