Machinery and processes of the industrial arts, and apparatus of the exact sciences (1869)
Barnard, Frederick A. P. (Frederick Augustus Porter), 1809-1889 · Washington, Govt. print. off. · leaf 556
advanced so far as to reflect the oppositehalf of the compound pencil, while it leaves theadjacent half free to pass. But if this prism, ofwhich the position can be controlled by means ofa slider, is drawn toward the extra tube so as to parts separated, reflect the nearer half of the compound… … 540 PARIS UNIVERSAL EXPOSITION. depressions and the depressions as reliefs. In the examination of an objectof obscure structure, the contrasts of appearance thus presented are oftenvery serviceable in contributing to the formation of correct judgments.It is a disadvantage common to all the forms of…
Machinery · Scientific apparatus and instruments
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