ELECTRICITY. 



281 



Max. Mllllroi. 



II vtlrocen 174 under pressure of 2.0 



Oxygen ..< ' " 0.7 



Air 172 " " 0.7 



aio Acid.... 168 " " 0.8 



I " " 1.0 



M. Morrcn remarks that the conductivity 

 of compound I::IM-S which the current dccora- 

 U generally very small, and commences 

 Thus carbonic oxide commences to allow 

 tho current to pass only under a pressure of 11 

 millims; carburetted hydrogen of 16 millims; 

 and sulphurous acid of 5 millims. Cyanogen 

 allows (ho current to pass under a pressure of 

 5 millitns. The passage of electricity through 

 rarefied cyanogen is accompanied by brilliant 

 luminous phenomena. 



The Passage of the Sparkofan Induction Coil 

 through Flamt. M. A. Kundt contributes to 

 Pogg. Annalcn for May, his observations on this 

 subject. He says that when the spark is passed 

 through tho flame the latter is intensely lumin- 

 ous in the path of tho spark, and under certain 

 circumstances a brightly luminous path of sparks 

 is traversed by dark cross bands. During the 

 transition of a spark the flame is always extin- 

 guished above ; but the part below the spark is 

 always constant and steady. Tho extinction of 

 the upper flame at each spark is supposed to be 

 due to the fact that the spark causes a very 

 rapid combustion of the gases in its path, and 

 then, by tho mechanical pressure which the 

 spark thereby exercises on all sides, the access 

 of gas from below is prevented for a moment. 

 The author viewed the phenomenon through a 

 rotating disk, in which there \vero several nar- 

 row slits. Viewed at right angles to the direc- 

 tion of the passing spark, the flame above the 

 spark seemed formed of bright and dark layers; 

 viewed in the direction of the spark, layers 

 in the proper sense were not seen, but dark cir- 

 cles continuously rising from the flame. It is 

 best for tho latter observation if one electrode 

 is in the flame, tho other remaining outside. 



Voltaic Conduction. The Philosophical 

 ~ine for January, 1866, contains a note 

 from J. J. Waterston, giving the results of an 

 experiment made by him to determine whether 

 tho electric force of tho voltaic pile is conveyed 

 by the entire thickness of the conductor, or by 

 the external surface only. He provided two 

 polished steel cylinders exactly alike, three 

 inches long and one-tenth of an inch in diam- 

 eter. One he covered with bright copper wire 

 one-hundredth of an inch in diameter, and the 

 other with steel wire, one-fiftieth of an inch in 

 diameter. The two cylinders were connected 

 end to end by a thin copper wire, the interval 

 bridged by the wire being about one-fourth of 

 an inch. The other ends of. tho cylinders were 

 similarly connected to the polar terminals of a 

 Bunscn cell half charged. These terminals wciv 

 made from a rope of No. 16 copper wire twisted 

 together, each wire about eighteen inches long. 

 After waiting two or three minutes this steel- 

 covered cylinder was found to be much hotter 



than tho copper-covered one. It was possible 

 to keep the copper-covered one pressed 1 

 lips tor a second or two, but not so the steel* 

 vd one. Tho temperatures were persist- 

 ent. Taking copper as having one-eighth the 

 resistance of steel, and tho rise of temperature 

 to be in tho inverse ratio of the fourth power 

 of the diameter of the cylinders, or conducting 

 wires, the temperature of these two cylinders 

 ought to bo nearly the same, if the force is con- 

 ducted by the whole thickness, instead of by the 

 surface alone ; whereas, if by the surface alone, 

 the rise of temperature in the steel-covered one 

 ought to be three or four times that in the 

 copper-covered one. 



St. Elmo's Fire. Captain Briggs, commander 

 of the steamer Talbot, furnished to Professor 

 Frankland an account of a splendid exhibition 

 of this rare electrical phenomenon, which oc- 

 curred in the Irish Channel on the 7th of March, 

 1866. During a snow-storm, which lasted three 

 hours, a blue light appeared at each masthead 

 of the steamer, and one from each gaff-end ; one 

 was also seen on the stemhead, which the cap- 

 tain examined. He found that the h'ght was 

 made up of a number of jets, each of which ex- 

 panded to the size of half-a-crown, of a beauti- 

 ful deep violet color, and making a hissing noise. 

 Placing his hand in contact with one of the 

 jets, a sensible warmth was felt, and three jets 

 attached themselves to as many fingers, but he 

 could observe no smell whatever. Sometimes 

 these jets went out, returning again when 

 the snow was heaviest. This was from one to 

 three, A. M. ; at daylight the captain carefully ex- 

 amined the place, but discovered no discolor- 

 ation of the paint. The stem in that part was 

 wood, with iron plates bolted on each side, and 

 it appeared to him that the jets came between 

 the wood and the iron. The barometer stood 

 at 29.10 in. The ship was an iron one, but he 

 did not observe any effect upon the compass. 

 He had seen the same phenomenon abroad, but 

 never before in these latitudes. 



An Electrical Paddle-Engine. Count de Mo- 

 lin is the designer of an electrical paddle-engine 

 which is adapted for a small boat intended to 

 ply on the large lake of the Bois de Boulogne, 

 and constructed as follows : There are two up- 

 right hoops, about two feet six inches in diam- 

 eter, placed three inches apart, in the periphery 

 of each of which arc encased sixteen electro- 

 magnets, placed opposite to each other. Be- 

 tween these there is another hoop, or wheel, of 

 soft iron, of tho same diameter as the others, 

 and so articulated as to receive, when alter- 

 nately attracted by the magnets, at each side, a 

 sort of rolling motion from side to side. To 

 this wheel is fixed an axis about seven feet long, 

 which forms the prime moving shaft of the 

 machine. "When tho wheel between tho mag- 

 nets takes its rolling motion, it causes the ends 

 of the axis to describe circles; one end turning 

 the crank of a fly-wheel, and the other being 

 adapted to a framework, on tho same principle 

 ns the pantagrapb, which enlarges the motion 



