I. The Bakerian Lecture.―On the stratifications and dark band in electrical discharges as observed in Torricellian vacua

Abstract

1. The striated condition of the electrical discharge in vacuo that takes place when the terminal wires of Ruhmkorff’s inductive coil are inserted into a well-exhausted receiver, in which a small piece of phosphorus has been previously placed, was first announced by Mr. Grove in his communication to the Royal Society, 7th January, 1852; his paper is printed in the first part of the Transactions for that year, and was subsequently published in the Philosophical Magazine of December 1852, with a supplementary note dated 9th June, wherein Mr. Grove states “ that he had found the transverse dark bands could be produced in other gases when much attenuated, probably in all, and that he thought the reason why they are more easily seen in phosphorus vapour is that all the oxygen having been consumed, a better vacuum is formed.” 2. I had, at the time, the pleasure of witnessing many of these experiments, which are now so well known to electricians; shortly afterwards I examined the discharge in a Torricellian vacuum: my apparatus consisted of a glass cylinder 6 inches long, in which two platinum wires are hermetically sealed about 4 inches apart; the cylinder forms the upper portion of a barometer, the lower part being made of the usual sized tubing; the mercury, when at the height of 30 inches, reaches to within about 6 inches of the cylinder; the mercury was carefully boiled in the usual manner by M. Negretti, and the apparatus fixed in my laboratory, where it at present remains as originally placed.