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Página 366 - TRANSACTIONS of the Society instituted at London for the Encouragement of Arts, Manufactures and Commerce, with the Premiums offered in the year 1783.
Página 22 - Hence it is clear that an under current outward of such denser water, if of equal breadth and depth with the current inward near the surface, would carry out as much salt below as is brought in above, although it moved with less than one fourth part of the velocity, and would thus prevent a perpetual increase of saltness in the Mediterranean Sea beyond that existing in the Atlantic.
Página 6 - The centre of this aperture must be in the common axis of the lenses ; and the image of the perforation formed by the large lens must be brought, by proper adjustment of the distance of that lens, into the same plane as the object to be examined. With a microscope so constructed, the author has seen the finest striae and serratures upon the scales of the lepisma and podura, and the scales upon a gnat's wing, with a degree of delicate perspicuity not attainable with any other microscope he has tried....
Página 137 - ... and in a subsequent paper, illustrated by some experiments on wood and metals pressed by springs of known intensity, he drew similar conclusions, with the addition that friction was one-third of the pressure, and that the amount was the same both with wood and metals when unguents were interposed. He likewise concluded, that friction increased or diminished with the velocity, and varied in the ratio of the weight and pressure of the rubbing parts, and the. times and velocities of their motions....
Página 3 - ... and brought to the eye, beyond that which is fully commanded by the object-glasses, tends rather to impede than to assist distinct vision. My endeavour has been, to collect as much of the admitted light as can be done by simple means, to a focus in the same plane as the object to be examined. For this purpose I have used with success a plane mirror to direct the light, and a plano-convex lens to collect it ; the plane side of the lens being towards the object to be illuminated.