— sound, xlix, 390.
— spark, W. R. Johnson, xxv, 57.
— —, length of, as affected by the size of the balls, W. R. Johnson, xxv, 60.
— —, perforations by, in a quire of paper or card, W. R. Johnson, xxv, 64.
— —, —, ibid, C. G. Page, xxxvi, 353.
— — drawn from a heated stove, xl, 385, 386.
— —, remarks on the so-called positive and negative, R. Hare, xxxii, 275.f
— —, Wheatstone's experiment to determine whether there is a sensible duration to, xxviii, 60.
— —, from magnets, J. Henry, xxii, 403.
— —, —, J. P. Emmet, xxiv, 78.f