Modern Practice of the Electric Telegraph: A Technical Handbook for Electricians, Managers, and Operators, with 185 Illustrations
D. Van Nostrand Company, 1891 - 234 стор.
Magnetismus, Elektromagnetismus ; Elektrotechnik ; Telegrafie (Nachrichtentechnik).
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action adjustment ampere-turns amperes apparatus armature artificial line battery brass centimetre chemical closed coil conducting conductor connected contact-points convenient copper plate copper wire cross-section deflection diagram diameter direction distant end distant station dots dynamo dynamo-electric earth effect electric circuit electric current electric telegraph electro-magnet electromotive force equal gauge glass gravity cell ground helix hence hydrometer illustration instrument insulation length less lever line-wire lines of force loop magnetic field magnetic force magnetic needle metallic miles number of cells number of turns Ohm's law ohms operator pegs placed pole position practical principle produced proportion quantity of current ratio resistance rheostat ring s. c. solution screws shown in Fig signals single-current soft iron sounder sulphate switch tangent galvanometer telegraph line telegraphic circuit termed terminal station thick tion transmitting unit usually vertical voltaic voltaic cell volts Wheatstone Bridge wire zinc zinc plate
Сторінка 36 - I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be.
Сторінка 223 - ... the artistic production. However, the intimate connection between content and form, even if the latter is designated as internal, seems to us a point well made, one that Brownson failed to emphasize sufficiently. For him the form was an object of care on the part of the artist merely for the reason that whatever is worth doing at all is worth doing well.
Сторінка 37 - Gauss' principle of absolute measurement for magnetism and electricity, is merely an extension of the astronomer's method of reckoning mass in terms of what we may call the universalgravitation unit of matter; and of the reckoning of force adopted by astronomers, in common with all workers in mathematical dynamics, according to which the unit of force is that force, which, acting on unit of mass for unit of time, generates a velocity equal to unit of velocity.
Сторінка 27 - ... electrical currents in the neighbourhood, without the presence of a magnet. Since the peculiarity of the magnetic field consists in the presence of a certain force, we may numerically express the properties of the field by measuring the strength and direction of the force, or, as it may be worded, the intensity of the field and the direction of the lines of force.
Сторінка 36 - In physical science a first essential step in the direction of learning any subject is to find principles of numerical reckoning and methods for practically measuring some quality connected with it. I often say that when you can measure what you are speaking about and express it in numbers, you know something about it ; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory...