Rudimentary Magnetism: Being a Concise Exposition of the General Principles of Magnetical Science and the Purposes to which it Has Been Applied ...

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Página 135 - A compilation from earlier historical works made, in the form in which we have it, at the end of the thirteenth or the beginning of the fourteenth century and known by the name of WALTER OF COVENTRY (W.
Página 55 - But whether elastic fluids do really consist of particles so repelling each other, is a physical question. We have here demonstrated mathematically the property of fluids consisting of particles of this kind, that hence philosophers may take occasion to discuss that question.
Página 102 - spot in which they have found the needle perpendicular — that is, the pole itself — is precisely that point on my globe and chart in which, by supposing all the lines to meet, the several curves would best preserve their unity of character, both separately and conjointly, as a system.
Página 11 - The power of gravity is of a different nature from the power of magnetism ; for the magnetic attraction is not as the matter attracted. Some bodies are attracted more by the magnet ; others less ; most bodies not at all. The power of magnetism in one and the same body may be increased and diminished ; and is sometimes far stronger, for the quantity of matter, than the power of gravity ; and in receding from the magnet decreases not in the duplicate but almost in the triplicate proportion of the distance,...
Página 113 - ... is the smallest number divisible at once by all the four periods, and hence the shortest time in which the four poles can accomplish a cycle. Now this time coincides exactly with the period in which the precession of the equinoxes completes its cycle. Certainly curious and remarkable series of coincidences.
Página 173 - ... one being the distance of the centre of the plate below the pivot of the needle, and the other its distance from the centre line of the pedestal ; and at this depth and distance in the line of no attraction, already mentioned, the plate is ultimately to be fixed.
Página 104 - From Toronto in Upper Canada to the Cape of Good Hope and Van Diemen's Land, from Paris to Pekin, the earth has been covered since 1828 with magnetic observatories...
Página 161 - Cook our illustrious navigator in his second voyage of discovery, stating distinctly that " variations observed with the ship's head in different positions, and even in different parts of her, will materially differ from one another ; and much more will observations observed on board different ships.
Página 117 - Europe, starting from the general principle that magnetism is distributed throughout the mass of the earth in an unknown manner, succeeded in obtaining, partly by theory and partly by adaptation, a sort of empirical formula, which represents in a wonderful way the many complicated phenomena of the magnetic lines, and has thus embodied our knowledge of them in a law mathematically expressed : —
Página 125 - ... indicated by the barometer, or caused by the presence or absence of the sun, changed in its magnetic relations. Further, every variation of temperature produces apparently its own change of force, in addition to that caused by the mere expansion or contraction in volume, and none of these alterations can happen without affecting the magnetic force emanating from the earth, and causing variations, both in its intensity and direction, at the earth's surface. Whether these changes are in the right...

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