Intelligence and Miscellaneous Articles. 21T> 



light disappeared. Two arc-lights were each time produced in two 

 glass bulbs, oue of which was inserted in the circuit. The strength 

 of the current was measured by an ammeter. 



The arc was found to be far shorter in hydrogen than in carbonic 

 acid, and in the latter, again, shorter than in air ; the ratio of the 

 lengths was about 3*9 : 7'4 : 8 # 5. In nitrogen, with an ascending 

 current, it is about 7 times as long as in hydrogen, and with a de- 

 scending current it is 25-7 times as long. "With decrease of pres- 

 sure the arc lengthens in nitrogen, hydrogen, and coal-gas ; in the 

 two latter, however, it never attains the same length as that of the 

 arc in air. 



With platinum electrodes the lengths of the arcs in carbonic 

 acid, nitrogen, coal-gas, and hydrogen at ordinary pressures were 

 in about the ratio 16 : 19 : 4-6 ': 2-8. 



The production of heat at the electrodes was determined for 

 various gases with sparks from a Ruhmkorff's inductorium. The 

 electrodes were thermoelements of iron and German silver. The 

 heating was investigated in two globes filled with various gases, in 

 which the distance between the electrodes was almost identical. 



The heating of the negative electrode was greater than with the 

 positive ; the difference of the heating effect seemed also to be 

 greater in nitrogen than in hydrogen. A globe filled with hydrogen or 

 with nitrogen was next used, through which the induction-spark was 

 passed, and the strength of the current measured by a well insu- 

 lated galvanometer. The induced discharge was more enfeebled 

 by a layer of hydrogen than by an equally thick one of nitrogen. 

 Moreover equally thick layers of hydrogen and nitrogen enfeebled 

 the discharge as much as columns of water of 99 and 59 millim. 

 respectively. 



In order to diminish the induction-current by the same amount, 

 the length of the spark in hydrogen was 33 millim., in nitrogen 

 48 millim., and in carbonic acid greater than 49 millim. Hence the 

 resistances were in the order — carbonic acid, nitrogen, hydrogen. 

 The heating of the electrodes increases with the rarefaction. 



The spark was then made to pass over the bulb of a mercurial ther- 

 mometer in various gases. The temperature increased more strongly 

 in nitrogen than in hydrogen both for the induction-spark and for 

 the spark from the battery-discharge. The heating with both was 

 much smaller in hydrogen than in nitrogen, so that in passing 

 through hydrogen the discharge has a much smaller electromag- 

 netic and thermal intensity than in passing through nitrogen. By 

 substituting for the spark other resistances the same result was ob- 

 tained. A layer of nitrogen 47*6 millim. in length enfeebles the 

 intensity of the induced current to the same extent as a layer of 

 hydrogen 36'95 millim. in length; and a layer of carbonic acid 49 

 millim. in length as much as a spark 33 millim. in length with the 

 battery -discharge. The negative electrode is almost as strongly 

 heated with the discharge in hydrogen as in nitrogen. With the 

 discharge of the condenser it is more heated in nitrogen. 



The spark was finally produced in glass tubes which were sur- 

 rounded by small calorimeters filled with oil of turpentine. uder 



