The Electrical Review, Τόμος 2Electrical review, Limited, 1874 |
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Δημοφιλή αποσπάσματα
Σελίδα 8 - IN ARITHMETICAL PROPORTION THE SUM OF THE EXTREMES is EQUAL TO THE SUM OF THE MEANS. 24. GEOMETRICAL' PROPORTION is AN EQUALITY OF GEOMETRICAL RATIOS, AND ARITHMETICAL PROPORTION AN EQUALITY OF ARITHMETICAL RATIOS.
Σελίδα 8 - But we would earnestly request that, whichever form of the word be employed, its meaning be strictly limited to the unit of force of the CGS system — that is to say, the force -which, acting upon a gramme of matter for a second, generates a velocity of a centimetre per second.
Σελίδα 71 - And if there were currents round the earth, regulated by some cause so as to give them a definite direction at one time, we are as far as ever from explaining how the channel of these currents could experience that great revolutionary variation which we know it does experience.
Σελίδα 72 - The result that we obtain every day of fair weather in ordinary observations on atmospheric electricity is precisely the same as if the earth were electrified negatively and the air had no electricity in it whatever.
Σελίδα 293 - This seems conclusive that the chemical electromotive force must be even greater than the contact electromotive force. This reversal of the current, by changing the seat of the chemical activity, may be shown in another way, depending on the application of a very old principle. If plates of copper and clean iron be connected by copper wires with a galvanometer, and the iron rendered passive by immersion for a moment in strong nitric acid, then if these plates are plunged into dilute nitric acid the...
Σελίδα 70 - It is not an expression we are accustomed to. We are accustomed to " terrestrial magnetism ; " we are accustomed to " atmospheric electricity." The electric telegraph forces us to combine our ideas with reference to terrestrial magnetism and atmospheric electricity. We must look upon the earth and the air as a whole — a globe of earth and air — and consider its electricity, whether at rest or in motion. Then, as to terrestrial magnetism, — of what its relation may be to perceptible electric...
Σελίδα 72 - I say that the statement that the air is positively electrified has been at all events a subject for ambiguous and contradictory propositions ; in fact, what we know by direct observation is, that the surface of the earth is negatively electrified, and positive electrification of the air is merely inferential. Suppose, for a moment, that there were no electricity whatever in the air — that the air were absolutely devoid of all electric manifestation, and that a charge of electricity were given...
Σελίδα 79 - For the better comprehending the relative position of the several places of observation, now embraced in our system of meteorology, an outline map of North America has been constructed, by Prof. Foreman. This map is intended also to be used for presenting the successive phases of the sky over the whole country, at different points of time, as far as reported...
Σελίδα 79 - The present time appears to be peculiarly auspicious for commencing an enterprise of the proposed kind. The citizens of the United States are now scattered over every part of the southern and western portion of...
Σελίδα 71 - They are always with us; let us see whether we cannot make something out of them since they have given us so much trouble. Now, if we could have simultaneous observations of the underground currents, of the three magnetic elements, and of the aurora, we should have a mass of evidence from which, I believe, without fail, we ought to be able to conclude an answer more or less definite to the question I have put.