A treatise of artificial magnets ; in which is shewn an easy and expeditious method of making them, superior to the best natural ones, and also, a way of improving the natural ones, and of changing or converting their poles : Directions are likewise given for making the mariner's needles. In the best form, and for touching them most advantageously, &c / by J. Michell.

  • John Michell
Date:
1750
Catalogue details

Licence: Public Domain Mark

Credit: A treatise of artificial magnets ; in which is shewn an easy and expeditious method of making them, superior to the best natural ones, and also, a way of improving the natural ones, and of changing or converting their poles : Directions are likewise given for making the mariner's needles. In the best form, and for touching them most advantageously, &c / by J. Michell. Source: Wellcome Collection.

    60/86 (page 58)
    In the following Table, the fir ft Column has feveral lengths for bars, in feet and inches. The fiecond, thews the weights, in pounds and ounces Avoirdupois, that bars of fuch lengths will bear. The third contains the number of fix-inch bars proper to touch them with. And the fourth, the number of fix-inch bars proper to fupport them with at each end. Feet. Inch. 1 2 3 4 5 6 8 Founds. Ounces. 4 4- Touched by. t - 2 _ 4 — 6 — 6 — io — H — 18 — 36 — 56 — 74 — 96 —170 —246 —33° Supported by. — 2 - 2 - 2 — 4 — 5 — 6 — 12 — 19 — 24 — 32 — 57 — 82 —110 The above Table is made out in vulgar frac¬ tions, as being the mod commonly known; ■f Thefe two muft be touched by two bars, after the manner of fmall bars; [See Page 35. ] and need not be fupported at all, . and