Proceedings of the Institution of Electrical Engineers Volume 19 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1891 Excerpt: ... in the chemical combination between the iron and the manganese. The effect of annealing was generally, but by no means invariably, to increase the permeability. The permeability was also found to be much greater for fine wires than for thick ones. Moreover, for a given strength of field it was increased by diminishing the size of the poles of the magnet producing the field, and by diminishing the distance separating them. On account of these variations it is necessary to calibrate each wire in fields of known strength. The author then draws a curve in which the abscissa) are the strengths of the field, and the ordinates the corresponding transverse stresses, and then determines the strength of an unknown field from the calculated transverse stress by interpolation. For accurate measurements the calibration must be made with poles of the same shape and distance apart as those which give rise to the field which is to be investigated, but the error introduced by varying the size and distance apart of the poles docs not exceed 5 per cent, of the strength of the field. E. WEBER-ATMOSPHERIC ELECTRICITY. Elektrotechnisclie Zeitschrift, Vol. 10, pp. 521 and 571, 1880.) This forms the fourth report presented by the author on this subject to the Electrotechnical Society of Berlin. The author's results, obtained by means of kites, show tliat there is a continuous rise of potential from the 6urface of thu s earth up to considerable heights, and he has found no indication of any diminution at still greater heights. He therefore inclines to Peltier's hypothesis of a negative terrestrial charge, in preference to that of Sir William Thomson, who supposes that while the earth itself is negatively charged, the higher layers of the atmosphere are charged positively. Assuming...