Appleton's dictionary of machines, mechanics, engine-work, and engineering : illustrated with four thousand engravings on wood ; in two volumes (1873)
D. Appleton and Company · New York : D. Appleton and Co. · leaf 323
^sr? … magnetic needles, with tlieir poles reversed to each other, are fixed on a central rigid axis, so as to neu-tralize the directive power of the needles, merely allowing a sufficient force to bring the whole into themeridian. This system is suspended by two parallel threads of unspun silk r n, one of…
Mechanical engineering · Mechanics · Engineering
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