412 RECENT PROGRESS IN PHYSICS. 



greater extent, when the opposite disc B was electrified positively 

 than when negatively. It therefore seemed as though negative elec- 

 tricity escaped from the pastile more easily ; while the positive, on 

 the contrary, was absorbed by it more readily. 



Biess explains tliese peculiar phenomena by the well known fact 

 that, in burning charcoal, a development of electricity takes place, 

 and, as observed by VoUa, this development is strongest with moder- 

 ate ignition, with a weak blast and a retarded combustion of the coal. 



In this case the ascending carbonic acid is positively, and the coal 

 negatively electrical ; the points being then negatively electrified 

 already of themselves, must act more powerfully when — E is im- 

 parted to them in addition, than when -f- E is imparted ; hence the 

 above described difference of the phenomena in positive and negative 

 charges explains itself perfectly. 



The coal acts by its negatively electrified points, and not through 

 the positively electrified steam, else we should obtain the stronger 

 effects with the same electrical charge, which, in the above experiment, 

 gave the weaker effect. This case is also observed in Davy's lamp 

 without flame. 



On the disk A (fig. 45) a brass flameless lamp with a feebly glow- 

 ing spiral was placed ; the lamp, 10 lines high, was surrounded by a 

 cylinder of sheet copper 13 lines high ; A being positively charged, 

 the electroscope b diverged more than by a negative charge of A. 

 When A was provided with an electroscope and B charged by conta,ct 

 with one of the poles of a dry pile, the electroscope diverged more by 

 a nes;ative charge of B. 



On the above mentioned memoir of Biess, a discussion lias arisen as 

 to the electrical effects of flame between Biess and Van Bees. — (Pogg. 

 Ann., LXXIII, pp. 41 and 307.) Vcm Bees first denies the existence 

 of steam points. He sustains himself by the fact that these points are 

 not visible when the shadow of a flame is examined, the shadow being 

 obtained by letting the light pass through the illuminating apparatus 

 of a solar microscope into a dark room, and bringing the flame into 

 the diverging cone of light. 



On the contrary, Biess says that he who imagines that these points 

 can cast shadows, may abandon this view without trying the experi- 

 ment. But it is a fact that, above the flame acting electrically, a 

 column of steam does exist, which is a good conductor, and which 

 soon loses itself in the badly conducting air ; the cold air divides 

 the conducting mass and diffuses it. 



Indeed, this view has the greatest probability on its side, and since 

 Van Bees himself says, "a flame is, on the whole, (including the 

 mass of steam directly above it,) to be regarded as a conductor," there 

 is properly no great difterence between the views of the two physicists, 

 and the controversy on this point is almost nothing but a strife about 

 words. 



In explaining the action of flame. Van Bees also starts from the 

 action of points ; he says, if a point be placed on the conductor of an 

 electrical machine, an unbroken current of electrified air arises, acting 

 inductively upon the nearest conductor. 



Two metres from the conductor of the electrical machine, furnished 



