ob- work in December, 1879, to invent an instru- server can calmly make his observations went that would yield the desired results. while concealed behind a wall, with the two His earliest design consisted of two strips extremities of the apparatus carrying the objectives projecting above the… … easy one. He decided to employ feet. The artilleryman will at once recognize the advantages that may the flame of a petroleum lamp with- be derived from so precise an ob- in a glass chimney, the radiation servation.” being limited by a circular opening The instrument under considera- of one…
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