[12] See Nature, vol. 55, p. 367 (Feb. 18th, 1897).
[13] Or, for best results, use a balanced metal disk covered with black velvet and white paper.
[12] See Nature, vol. 55, p. 367 (Feb. 18th, 1897).
[13] Or, for best results, use a balanced metal disk covered with black velvet and white paper.