Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER II. Second Period.— From Hittorf To Lenard. The publication in 1869 of W. Hittorf's first paper on the electrical conductivity of gases (1) may be rightly looked upon as the beginning of a new period in the study of this subject. Heretofore there had been more or less casting about and a lack of definiteness; but henceforth a more systematic study of the discharge of electricity through gases was instituted. Observations were more accurate, new facts were discovered, their theoretical bearing was discussed and a successful attempt was made to analyse some of the more complicated phenomena. All this was due mainly to the efforts of such men as W. Hittorf, E. Goldstein, the two Wiedemanns, Sir W. Crookes, J. J. Thomson and several others. I.— W. Hittobf. Faraday had already described the appearance of the electric discharge in rarefied gases. Although many experimenters intervened between him and Hittorf, the latter may be looked upon as continuing the former's work, for he prefaced his first paper by an extensive extract from Faraday's Experimental Researches and then pursued his own investigations on similar lines but under more favorable conditions. These allowed him to get a higher E. M. F. and higher vacua, thanks to the improvements made in the Rhumkorff coil and (1) Pogg. Ann. 136, p. 1, 1869. the mercury pumps constructed by Geissler. By the aid of these new appliances, he noted (1) that as the gas pressure became lower than 2mm of mercury, there was a rapid change in the phenomena observed by Faraday. The glow on the kathode soon extended itself not only over greater portions of this electrode but also throughout the surrounding space driving back all the while the reddish light towards the anode. Both lights became striated with a concavity toward...