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Page 292 - Fig. 5 as connected. In order to place the commutator in a convenient position, the terminal wires are carried through the centre of the shaft, to a point outside the bearings. The commutators are so arranged, that, at any instant, three pairs of coils are interposed in the circuit of the machine, working, as it were, in multiple arc, the remaining pair being cut out at the neutral point...
Page 38 - At first sight it seems rather difficult to believe that an ignited gas in the solar envelope should not be indicated by dark lines in the solar spectrum, and should appear not to act under the law " a gas when ignited absorbs rays of the same refrangibility as those it emits.
Page 296 - ... by many previous experimenters. The difficulties encountered in the measurement of the light, arising from the difference in colour, were at first thought to be considerable, but further practice and experience enabled the observer to overcome them to such an extent, that the error arising from this cause is inconsiderable, being greatly less than that due to the fluctuations of the electric arc itself.
Page 362 - With this arrangement, no difficulty was experienced in reproducing the same conditions of normal running as when the arc was used. The same conducting wires were used throughout these experiments. Being of heavy copper, their resistance was low, viz.: about '016 ohm.
Page 370 - For example, the heat in arc and lamp are practically the same in each of the Brush machines, if the measurement of the smaller of these machines be taken at the higher speed. The amount of light produced, however, is not the same in these two instances, being considerably greater in the case of the larger machine. The explanation of this apparent anomaly is undoubtedly to be found in the different resistances of the arcs in the two cases. In the large Brush machine the carbons are nearer together...
Page 135 - There were present 163 members and 5 visitors. The minutes of the last meeting were read and approved. The Actuary presented the minutes of the Board of Managers and reported that...
Page 366 - No determination made with an unknown or abnormal external resistance can be of any value, since the proportion of work done, in the several portions of an electrical circuit, depends upon, and varies with, the resistances they offer to its passage. If, therefore, in separate determinations with any particular machine, the resistance of that part of a circuit of which the work is measured be in one instance large in proportion to the remainder of the circuit, and in another small, the two measurements...
Page 419 - Science, having learned with great satisfaction, that a convention has been entered Into by the leading nations of the world for the establishment and maintenance of an International Bureau of Weights and Measures, with the object of promoting permanence, precision and uniformity In the standards, at the joint charge of the contracting powers; and that the Government of the United States has agreed to the same through its diplomatic...
Page 133 - December 20, at Paris, of Henry Daniel Ruhmkorff, whose name is so closely connected with the history of magnetoelectricity. He was born in Hanover, Germany, in 1803, and but little is known of his early life. In 1819 he wandered to Paris, and obtained a position as porter in the laboratory of Prof. Charles Chevalier, at that time one of the leading French physicists. Here he displayed a remarkable fondness for electrical apparatus, as well as ingenuity in its arrangement, and was enabled shortly...
Page 374 - Gramme, having, however, the disadvantages of high speed, and a greater proportionate loss of power in friction, etc. This loss is nearly compensated by the advantage this machine possesses over the others of working with a high external, compared with the internal, resistance, this also ensuring comparative absence of heating in the machine. This machine gave the most powerful current, and consequently the greatest light.