A System of Mechanical Philosophy, Volume 4

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J. Murray, 1822 - Mechanics - 50 pages
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Page 402 - A stopcock was so constructed that it opened and shut the passage of a pipe 720 times in a second. The apparatus was fitted to the pipe of a conduit leading from the bellows to the wind-chest of an organ. The air was simply allowed to pass gently along this pipe by the opening of the cock. When this was repeated 720 times in a second, the sound g in alt was most smoothly uttered, equal in sweetness to a clear female voice.
Page 373 - ... between this meteor and magnetism. This should farther incite us to observe the circumstance formerly mentioned^ viz. that the south end of the dipping needle points to that part of the heavens where the rays of the aurora appear to converge. We wish that this were diligently observed in places which have very different variation and dip of the mariner's needle. For the diurnal and this irregular variation, consult the Dissertations of Celsius and of Hiorter, in the Memoirs of Stockholm; Wargentin,...
Page 209 - Elsewhere, Prof. Robison remarks : " It is not saying too much of this work to affirm that it contains almost everything we know of magnetism. His unwearied diligence in searching every writing on the subject and in getting information from navigators, and his incessant occupation in experiments, have left very few facts unknown to him. We meet with many things in the writings of posterior inquirers, some of them of high reputation and of the present day, which are published and received as notable...
Page 543 - PC, the tooth B continues to press on the pallet D, and thus accelerates the pendulum, both during its descent along the arch PH, and its ascent along the arch HG. It is no less evident, that when the pallet D, by turning round the axis XY, raises its point above the plane of the wheel, the tooth B escapes from it, and i drops on the pallet c, which is now nearly perpendicular. i presses c; to the right, and accelerates the motion of the pendulum along the arch GP. Nothing can be more obvious than...
Page 678 - If the maidtopsail be aback, the ship shoots a-head, and comes up till the diminished impulse of the drawing sails in the direction of the keel is balanced by the increased impulse on the main topsail. She lies a long while in this position driving slowly to leeward ; and she at last falls off by the beating of the water on her weather-bow. She falls off but little, and soon comes up again. Thus a ship lying to is not like a mere log, but has a certain motion which keeps her under command.
Page 609 - We are as little entitled to expect improvement here as in the architecture of the bee or the beaver. Yet a ship is a machine. We know the forces which act on it, and we know the results of its construction — all these are as fixed as the laws of motion. What hinders this to be reduced to a set of practical maxims, as well founded and as logically deduced as the working of a steam-engine or a cotton-mill?
Page 646 - M a lever acted on in different parts by forces in different directions, and the whole balancing each other round that point or axis where the equivalent of all the resisting forces passes. This may be considered as a point supported by this resisting force, and as a sort of fulcrum : therefore, in order that the ship may maintain her position, the energies or momenta of all the impelling forces round this point must balance each other.
Page 352 - COMPASS, or the declination of the magnetic or mariner's needle from the meridian or true north and south line at the undermentioned places in the United Kingdom, estimated for the year 1875. NB — The variation is westerly, that is, the magnetic pole is west of the true north pole, and is found to be decreasing in the United Kingdom about 9
Page 673 - ... uncertain ; for the action of the water on the rudder may not be nearly equal to its contrary action on the lee-quarter ; in which case the action of the wind on the headsails may not be sufficient to make up the difference. When this is...
Page 373 - This is probably the effect of auroras boreales which are invisible, either on account of thick weather or day-light. Van Swinden says he seldom or never failed to observe aurora boreales immediately after any anomalous motion of the needle ; and concluded that there had been one at the time, though he could not see it. Since no needle but a magnetic one is affected by the aurora borealis, we may conclude that there is some natural connexion between this meteor and magnetism.

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