Intelligence and Miscellaneous Articles, 153 



Mountains (lat. m°-dT JST.). In Northern Italy (about lat. 45°- 

 46° jS".) glaciers were a great deal larger in Postpliocene times than 

 at present. 



4. " The Action of Coast-ice on an oscillating area," By Prof. 

 John Milne, F.G.S., of the Imperial College of Engineering, Tokio, 

 Japan. 



In this paper the author described the results of observations 

 made by him in Newfoundland, Labrador, and Pinland, which had 

 led him to believe that many of the marks generally regarded as 

 furnishing evidence of the existence of an ice-cap, or at least of an 

 enormous extension of land-ice at certain periods, might easily be 

 explained by the action of coast-ice upon an oscillating, and espe- 

 cially a rising area. 



XX. Intelliqence and Miscellaneous Articles, 



ON THE SPECTRUM OF THE ELECTEIC SPAEK IN A COMPRESSED 



GAS. BY A. CAZIN. 

 TT is generally admitted, from the observations of Wtillner, 

 -^ Erankland, Lockyer, and Cailletet, that the spectral lines of an 

 incandescent gas become more and more spread as the pressure is 

 augmented, and under a sufheient pressure unite to form a conti- 

 nuous spectrum. I am led by my own observations upon air and 

 nitrogen to the following proposition : — '' The electric spark in a 

 gas is analogous to the flame of an ordinary hydrocarbon." In 

 each of these sources of light there are gaseous particles, which 

 produce a line spectrum, and solid or liquid particles, which pro- 

 duce a continuous spectrum. In the spark the latter come from 

 the electrodes, and from the sides when these are very close. 

 When the pressure is increased, these particles become more abun- 

 dant, their continuous spectrum grows brighter, and at last causes 

 the line spectrum of the gaseous particles to disappear. 



It is in the fiery trail that things happen thus ; the paler lumi- 

 nous sheath called the aureole is formed of gaseous particles, the 

 line spectrum of which is more or less visible : it is to the total 

 spark what the blue base of the flame of a taper is to the entire 

 flame. 



My first experiments on this subject are of the month of May 

 1876, and were at that time communicated to the Societe Philo- 

 matique. I observed the spectrum by means of an ordinary spec- 

 troscope with a single, very dispersive prism. The gas was com- 

 pressed in a glass tube by aid of a sort of mercury piezometer. A 

 platinum v/ire is soldered to the upper end of the tube ; a second 

 wire, similar, is kept, inside, parallel to the preceding by an iron 

 wire fixed to the bottom of the tube and which dips in the mer- 

 cury. A large Euhmkorff coil produces the spark between the 

 platinum wires ; and its image is thrown by a lens upon the slit of 

 the spectroscope. 



