372 Intelligence and Miscellaneous Articles. 



because I have just read in a foreign scientific journal* an account 

 of similar experiments made at Strasburg with apparatus arranged 

 like that which I have just described. In those experiments MM. 

 Kundt and Eontgen ascertained, without being able to measure it, 

 the magnetic rotatory power of sulphide of carbon, sulphuretted 

 hydrogen gas, and gaseous sulphurous acid. 



There is, however, a considerable difference, in respect of the 

 results that can be obtained by this method, between the apparatus 

 which I use and that employed by the Grerman physicists. This 

 difference arises from the nature of the tube for containing- the 

 vapour. My tube is of brass, while that at Strasburg is of iron. 

 This latter therefore constitutes a large hollow electromagnet having 

 in its interior the gases which are to be investigated. 



To show the inconvenience presented by such, an arrangement, I 

 will cite the following experiment. A tube filled with sulphide of 

 carbon is placed between the poles of a Faraday electromagnet ; it 

 gives a rotation of 10° 30'. On introducing this tube inside one 

 of the two hollow electromagnets of the same apparatus, and 

 passing into this single electromagnet the whole current of the pile, 

 no appreciable rotation is observed. 



It is true that when the iron tube of the electromagnet is thinner 

 the action is not entirely annulled ; but it is always considerably 

 diminished. Thus a hollow bobbin 20 centims. in length, con- 

 taining a tube filled with sulphide of carbon, gives a rotation of 5° ; 

 if an iron tube of 2*5 millims. thickness be placed in the bobbin, the 

 rotation is not more than 1°. 



These experiments, moreover, only confirm the theory of hollow 

 magnets, given by M. Bertin nearly twenty-five years since t. — 

 Gomptes JRendus de V Academic des Sciences, March 31, 1879, 

 t, lxxxviii. pp. 712, 713. 



ON AN ELECTRICAL BURNER AND BLOWPIPE. 

 BY M. JAMIN. 

 The electric arc that springs between two carbon conductors is a 

 true current. "When submitted to the near influence of a current, 

 a selenoid, or of a magnet, it undergoes an action governed by 

 Ampere's laws, identical with that which would be undergone by 

 any metallic conductor put in its place ; but as the mass of the 

 material of which it consists is very little, the velocities it takes are 

 considerable. It can be attracted, repelled, displaced, fixed, caused 

 to rotate — in a word, made to go through all the motions that can 

 be impressed upon movable currents in electromagnetic experi- 

 ments. The first action of this sort was observed by M. Quet, who 

 projected horizontally, in the shape of a dart, a vertical arc between 

 the two horizontal poles of an electromagnet. A multitude of 

 similar experiments can be made ; I shall today content myself with 

 citing the following. 



* "Wiedemann's Annalen. 1879, No. 3, p. 332. See Phil. Mag. March 

 1879, p. 173. 



f Ann, de Chim. et de Phys, (3) lviii. p. 90. 



