An Essay on Electricity: Explaining the Principles of that Useful Science, and Describing the Instruments, Contrived Either to Illustrate the Theory, Or Render the Practice Entertaining : Illustrated with Six Plates. To which is Added, a Letter to the Author, from Mr. John Birch, Surgeon, on the Subject of Medical Electricity

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J. Dillon, and Company, for, and sold by W. and S. Jones, 1799 - Electricity - 594 pages
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Page xiv - AN ESSAY ON VISION, briefly explaining the Fabric of the Eye, and the Nature of Vision...
Page 99 - C, standing on the floor, both appear to be electrized; for he, having only the middle quantity of electrical fire, receives a spark upon approaching B, who has an over quantity ; but gives one to A, who has an under quantity. If A and B approach to touch each other, the spark is stronger, because the difference between them is greater. After such touch there is no spark between either of them and C, because the electrical fire in all is reduced to the original equality.
Page 335 - Let a person standing on the floor present the point of a needle at twelve or more inches distance from it, and while the needle is so presented, the conductor cannot be charged, the point drawing off the fire as fast as it is thrown on by the electrical globe. Let it be charged, and then present the point at the same distance, and it will suddenly be discharged.
Page 391 - Hj fastened to the tube by means of a cork; the upper extremity of the wire projects about a quarter of an inch above the tube, and screws into the brass cap...
Page 315 - ... determined by this means ; for I have known instances, during the course of these experiments, where a small particle of air having found its way into the tube, the electric light became visible, and as usual of a green color; but the charge being often repeated, the gage has at length cracked at its sealed end, and in consequence the external air, by being admitted into the inside, has gradually produced a change in the electric light from green to blue, from blue to indigo, and so on to violet...
Page 472 - When the electric spark was made to pass through common air, included between short columns of a solution of litmus, the solution acquired a red colour, and the air was diminished, conformably to what was observed by Dr. Priestley. When lime-water was used instead of the solution of litmus, and the spark was continued till the air could be no further diminished, not the least cloud could be perceived in the lime-water ; but the air was reduced to twothirds of its original bulk ; which is a greater...
Page 473 - what degree of purity the air should be of, in order to be diminished most readily, and to the greatest degree.
Page 71 - ... according as they were taken off; except the most remote, which always kept an electricity opposite to that of the plate. The following experiments were performed by Mr Nicholson, on an improved method of excitation, as well as the action of points, and the direction of the fluid in positive and negative electricity. 1 . A glass cylinder was mounted, and a cushion applied with a silk flap, proceeding from the edge of the cushion over its surface, and thence half round the cylinder. The cylinder...
Page 407 - C, two inches in diameter, separately inę sulated and placed in the same plane, so that a revolving plate B may pass near them without touching. A brass ball D, two inches in diameter, is fixed on the end of the axis that carries the plate, B, and is loaded within at one side to act as a counterpoise to the revolving plate B, so as to keep it at rest in any position. The axis PO is made of varnished glass, and so...
Page 73 - M of the silk is not merely to prevent the return of electricity from the cylinder to the cushion, but that it is the chief agent in the excitation, while the cushion serves only to supply the electricity, and perhaps increase the pressure at the entering part. There likewise seems to be little reason to doubt. but that the disposition of the electricity to escape from the surface of the cylinder, is not prevented by the interposition of the silk, but by a compensation after the manner of a charge...

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