This historic book may have numerous typos and missing text.
Purchasers can download a free scanned copy of the original book
(without typos) from the publisher. Not indexed. Not
illustrated.1887 Excerpt: ... 250 ABSTRACTS. LORD RAYLEIGH--ON
PROFESSOR HIMSTEDT'S DETERMINATION OP THE OHM. (Phil. Mag., Vol.
21, No. 128, Jan., 1886, pp. 10-18.) The leading feature in the
method of Professor Himstedt is the use of a commutator or
separator, by which the make-and break--induced currents are
dissociated, one or the other passing in a stream at equal small
intervals of time through a galvanometer. The commutator makes
contact by means of mercury cups, and Lord Rayleigh points out how
very capricious and uncertain such contacts are in their action. A
second point raised relates to the measurement by the galvanometer
of a series of induced currents, each of short duration. In
Himstedt's method the needle of the galvanometer stands in an
oblique position, and we have to consider whether the axial
magnetisation does not alter under the action of a force having a
sensible axial component. There is yet a third point which may be
open to objection, viz., the determination of K, the constant
expressing the number of turns of the primary of the induction coil
per unit of length. Apparently the value of K is arrived at by
dividing the whole number of turns, 2,864, by the total measured
length, 135-125 cm.; but in so doing it is assumed tacitly that the
turns are all perfectly uniform, or that only the mean value is
required, both of which assumptions may be questioned. Professor E.
J. HOUSTON--PHOTOGRAPHY KY A LIGHTNING FLASH. (Journal FranhUn
Inttitute, Vol. 91, No. 8, March, 1886, pp. 221-22.) The view taken
was that of the surrounding country near Philadelphia at 7 p.m. on
the 29th Oct., 1883. The night was excessively dark, with much wind
and rain. The camera was placed at an open window, with the slide
drawn, and immediately after the flash the slide was returned. The
General Books LLC
|Country of origin:
Institution of Electrical Engineers
||246 x 189 x 13mm (L x W x T)
||Paperback - Trade
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