If a small magnet of moment M is placed in the sensibly uniform field H due to a distant magnet, the couple tending to turn the small magnet upon an axis at right angles to the magnet and to the force is MH sin 0, (17) where 0 is the angle between the axis of the magnet and the direction of the force.
The product MH is first determined by suspending the magnet horizontally, and causing it to vibrate in small arcs.
We get therefore M 2 = MH X M/H = 27r 2 A(d 2 - l 2) 2 tan 0/t 2 d (42) s H 2 =Mhxh/M = 87r 2 Ad/tt 2 (d 2 -1 2) 2 tan B} (43) When a high degree of accuracy is required, the experiments and calculations are less simple, and various corrections are applied.
Thus if the magnet is suspended horizontally by a fine wire, which, when the magnetic axis points north and south, is free from torsion, and if 0 is the angle through which the upper end of the wire must be twisted to make the magnet point east and west, then MH = CB, or M = C6/H, where C is the torsional couple for r 0.
If P is the weight of the magnet, l the length of each of the two threads, 2a the distance between their upper points of attachment, and 2b that between the lower points, then, approximately, MH = P(ab/l) sin 0.
The breadth of the trapezette being mh, it may be shown that its area is 2 2 N 4 4 iv I mh ug m + 24 m h u gm + 1920 m h u g m + 322560 no/tourgm -}- m3l1gu i„?
It gives origin to three classes of salts: M'H 2 PO 4 or M"H 4 P 2 0 8; M' 2 HPO 4 or M"HP04, M'3P04, M" 3 P 2 0 8 or M"'PO 4, wherein ll',M",M"' denote a mono-, di-, and tri-valent metal.
(K,Na,NH 4)H 5 (PO 4)2, are also known; these may be regarded as composed of a monometallic phosphate with phosphoric acid, thus M'H 2 PO 4 H 3 PO 4.
Microcosmic salt: MH 2 PO 4 = MP0 3 +H 2 0, (NH 4) NaHPO 4 = NaP03+NH3+H20; they may also be obtained by acting with phosphorus pentoxide on trimetallic orthophosphates: Na3P04+P205 = 3NaP0 3.
Voiceless nasals: mh; nh; ngh.
(2) After nasals p, t, c, b, d, g became respectively mh, nh, ngh, m, n, ng; thus 2mperator gave ymherawdr, and ambactos (evidently a Brythonic as well as a Gaulish word) gave amaeth (m, though etymologically double, is written single).