Prof. E. Wartmarm's Fifth Memoir on Induction. 91 



reflected, refracted and polarized. The experiments which I 

 proceed to describe were made at the invitation and with the 

 assistance of my friend M. Ch. Cellerier. They are in a man- 

 ner well-timed from the recent publication of Prof. Maas*. 



150. The apparatus employed is represented in plan in 

 Plate I. fig. 1, and a section of it in fig. 2. AB is a glass tube 

 one metre in length, perforated by a small internal canal, and 

 arranged horizontally. One end terminates at the bottom of 

 a vertical chamber C, of the same substance, and the other at 

 the centre of a cylindrical earthen vessel DD', into which it 

 penetrates by an aperture which is closed by means of a stopper 

 a. The vessel is divided into two equal chambers, isolated by 

 the plate of glass bb, cemented in a perpendicular position to 

 the axis of the tube. All the sides of these two chambers 

 were covered with several layers of varnish of gum-lac. On 

 the middle of the plate was fixed a piece figured in detail in 

 fig. 3. It is composed of a large copper cylinder, the foot 

 of which is slit at e. The excentricity of this slit allowed 

 of the vertical axis, to which it is parallel, being made to co- 

 incide exactly with the mouthpiece v of the tube AB. Higher 

 up is seen a diametral aperture^ into which is fixed, by the 

 screw g, the extremity of the wire oca. Lastly, the upper part 

 of the cylinder dd is pierced in the direction of the axis for 

 the length of () m, 035, with a slightly conical aperture, in 

 which the piece h turns with gentle friction. This piece is 

 furnished with a support which regulates its insertion. At its 

 extremity, this piece has a square hole which receives the stem 

 I held tight by the screw k. The arm i is itself pierced so as 

 to receive the copper wire Z, the serviceable length of which is 

 regulated by the screw n, and the lower part of which, isolated 

 in a glass tube m, is exposed only at the base of the latter. 



151. The experiment is made with a voltaic element P, the 

 nature of which varies according to the sensibility of the rheo- 

 meter G. The first experiments were performed with a pair 

 formed of two square plates, copper and zinc, of m, 035 thick- 

 ness ; the others with a copper and an iron wire immersed in 

 pure water. The polar extremities terminate in the mercury 

 contained in the glasses p and q. 



152. These glasses communicate with two other similar 

 cups E, F, by means of the metallic branches r and s, in fig. 4. 

 The first, r, is a large copper wire curved twice, and the hori- 

 zontal portion of which is inclosed in a glass tube ; the other, 

 5, is a wire of the same diameter with three bends : its central 



* Considerations sur le movement de la Dynamie Electrique: Bulletins 

 de VAcadcmie Rot/ale de Bruxelles, July 10, 1847. U Institut of Jan. 5, 



1848. 



