Intelligence and Miscellaneous Articles. 465 



The mind is proverbially tenacious of first impressions ; and the 

 chief idea that an imperfectly scientific audience would have carried 

 away from the lecture in question, is that electricity is a form or 

 kind of matter, and not a mode of motion, or phase of dynamic 

 energy. I am, Gentlemen, 



Yours faithfully, 

 16 Fitzroy Square, May 23, 1870. Charles Brooke. 



RESULTS OF A RESEARCH ON THE ABSORPTION-SPECTRUM OF 

 IODINE-VAPOUR. BY ROBERT THALEN*. 



From my investigations on the absorption of iodine-vapour I have 

 arrived at the following results f : — 



1. The dark bands on the absorption-spectrum of iodine do not 

 extend the entire length of the visible spectrum, but only to the half 

 between the red and green parts. 



2. When the absorption has reached its maximum (that is, when 

 the absorbed part of the spectrum forms almost a single continuous 

 band) the violet part still remains without the smallest change ; hence 

 originates the violet colour characteristic of iodine-vapour. 



3. The successive bands do not form a single series, but several 

 mixed with each other — a fact which may be very distinctly recog- 

 nized in the periodical changes which the intensity of the bands pre- 

 sents. 



4. The bands belonging to a given series are not equidistant ; but 

 their mutual distances increase progressively with the wave-lengths, 

 though they are not proportional to them. 



5. Each band may be resolved into several very fine lines which 

 form among themselves more or less regular groups. 



ON A SIMPLE METHOD OF DISPENSING WITH OBSERVATIONS OF 

 TEMPERATURE AND PRESSURE IN GAS-ANALYSES. BY WOLCOTT 

 GIBBS, M.D.J 



In absolute determinations of nitrogen and other gases, accurate 

 observations of temperature and pressure are, in the ordinary methods 

 of analysis, necessary, and when made require subsequent calcula- 

 tions which, when the analyses are numerous, become rather tedious. 

 By the following simple method these observations may be altogether 

 dispensed with, and the true weight or the reduced volume of the 



* From an abstract communicated by the author to PoggendorfF's An- 

 nalen — the complete paper, with three large copperplates, having appeared 

 in the Kongl. Svenska Vetensk. Acad. Handl. for 1869. 



T In all these investigations I made use of six flint-glass prisms of 60° ; 

 and the spectroscope was that which I used both for drawing the violet 

 part between G and H of the solar spectrum (" On the Fraunhofer Lines, 

 together with a Diagram of the Violet parts of the Solar Spectrum," by A. 



o 



J. Angstrom and R. Thalen, K. Vet. Acad. Handl. 1865), and in the de- 

 termination of the wave-lengths of the metal lines (" Mem. sur lade'termi- 

 nation des longueurs d'onde des raies metalliques," par R. Thalen, Nova 

 Acta Soc. Sc. Ups. vol. vi. 1868). 



% Read before the National Academy of Sciences, September 1869. 

 Phil. Mag. S. 4. Vol. 39. No. 263. June 1870. 2 H 



