The most remarkable exception is common salt itself, the solution of which was one in 29, and therefore in 1116 there were 37.2 parts of salt. Now the equivalent of NaCl is 585, which is very much. greater. Besides this the conductivity of a solution of salt in 29 of water would be much less in comparison with that of the other solutions than would appear from Cavendish's results, whereas if we assume that the molecular strength of the salt solution was really the same as that of the other solutions, the numbers do not differ much from those given by Kohlrausch. The following table shows the results obtained by Cavendish and by Kohlrausch. The theory of the electric resistance of electrolytes has been put on an entirely new footing by M. F. Kohlrausch, who has not only measured the resistance of a large number of solutions of different strengths and at different temperatures, but has discovered that the conductivity of a dilute solution of any electrolyte in water is the sum of two quantities, which we may call the specific conductivities of the components of the electrolyte, multiplied by the number of electro-chemical equivalents of the electrolyte in unit of volume of the solution. (Since the components of an electrolyte are not themselves electrolytes, it is manifest that they can have no actual conductivity, but the number to which we may give that name is such that when any two ions are actually combined into an electrolyte, the conductivity of the electrolyte depends on the sum of their respective numbers.) Kohlrausch has also calculated the actual average velocity in millimetres per second with which the components are carried through the solution under an electromotive force of one volt per millimetre; and on the hypothesis that the components are charged with the electricity which travels with them, he has calculated the force in kilogrammes weight which must act on a milligramme of the component in order to make its average velocity in the solution one millimetre per second. It appears to me that the simplest measure of the specific conductivity of an ion is the time during which we must suppose the electric force to act upon it so as to generate twice its actual average velocity. If we suppose that all the molecules of the ion are acted on by the electromotive force, but that each of them is brought to rest by a collision with a molecule of the opposite kind n times in a second, then According to the theory of Clausius, it is only a small proportion, Since the time 7 is very small, it is more convenient to speak of On the Ratio of the Charge of a Globe to that of a Circle of the same Diameter. The true value of this ratio is = 1.570796.... Cavendish has given several different values as the results of his In the account of his experiments, which represents his most matured All the other values, however, either as stated by Cavendish or In Art. 281 the charge of the globe of 12.1 inches diameter being 1, In Art. 445 the charge of the globe is compared with that of I thus find 14.2 or 14.3 for the charge of the globe, and 15-2 for In Art. 456 the ratio as deduced by Cavendish from the observations From the numerical data given in the same article, the ratio would Cavendish evidently thought the result given here of some value, for Another set of observations is recorded in Art. 478, from which we It appears by a comparison of Arts. 506 and 581 that Cavendish, at At Art. 648 the ratio is stated as 1.54. At Art. 654 measures are given from which we deduce 1.542 and The numbers in Art. 682 are the same as those in Art. 281. ALPHABETICAL INDEX. The references are to the Articles. A. A, coated plate of glass so called, "First Epinus (Franz Ulrich Theodor, b. 1724, Basket salt 628 Beech 590, 609 Bees'-wax 336, 371, 376 Brass plate of trial plate 297 Breaking of electricity through plates 520 C. Calc. S. S. A. 626, 694 and note 34 Canal 40, 68, 69; bent 48, 49, 84-95 Canton, John, F.R.S. (1718--1772) 117, 205 Cement 303, 484, 497 Centre of suspension 388 Chain machine 433, 605, 613 Charge defined 237; does not depend see Tables; of battery 412; divided Charging jar 223, 225 Circles 273 Circuit, divided 397, 417 Coated plates 300, 314, 441; theory of, 74, 160, 169; lists of, see Tables 133 Column 145-147 Communication 100, 219; of charge to Comparison of charges 236 Compound plate 379-381, 560, 677— Compression (or pressure) 179; distin- guished from condensation 200 Conduction by hot glass 369 Conductivity 469, 491; of straws 565 Cone, attraction on particle at vertex 7 124 and note 9 Contact 306; impossible 196 note; of brass and glass 541, 558 Copper wire, resistance of 636–646 Crown glass 301, 330, 378, 411, 430, Cylinder 54, 148-151; charge of 281, D. D, coated plate 483, 487 Deficient fluid 67, note Communication 100 Condensation 200 Deficient fluid 67, note Inches of electricity, circular 458, 648; Degrees of electrification 329, 356; of Dephlegmated wax 371, 375, 518 Dividing machine 341, 459, 517, 591 E. and F. 457 E. Earth connexion 258, 271 Electric crgan of torpedo 396, note 29 Electrification, degree of 102, 201 and Electrodes, large 258, 271 Cavendish's discharging 402, 405, 427, gauge (paper cylinders) 224, 248, 295, Divisions of 560, note Henly's 559, 568, 570, 571, 580; on Lane's 263, 329, 559, 569, 570, 571, 580, 589, 603, 604 Paper cylinders 486 Pith ball 581 Straw 249, 404, 559, 570, 571, 581; |