16 REPORT — 1867. 



Mr. C. W. Siemens, F.E.S., of London, having been asked by Messrs. Stevenson 

 for suggestions as to the best means to be adopted for carrj-ing out Mr. T. Stevenson's 

 proposal for producing a flashing light upon a beacon, by means of a land battery 

 connected to the beacon through a submarine cable, embodied his views in a letter 

 addressed by him to Messrs. Stevenson on the 1st October 1866. After reviewing 

 the objections to other methods, he recommended the application of the extra- 

 cim-ent together with a self-feeding mercui-y contact, as the only practical method 

 in which the flash is not destroyed by electric charge of the connecting cable. Mr. 

 Siemens having been authorized [by the Northern Light Commissioners to con- 

 struct an apparatus in accordance with his views, has submitted the same to a suc- 

 cessful trial. 



The apparatus upon the beacon or buoy consists of a heavy electromagnet, the 

 coils of which are permanently connected with the conducting wire of the cable on 

 the one hand, and with a contact lever on the other hand, which contact lever is 

 actuated by the armature of the electromagnet in the mamier of a nefts hammer. 

 The circuit with the battery (consisting of fi'om ten to twenty Bunsen's elements) 

 on land is completed through the sea. When the cun-ent has had time to excite the 

 electromagnet sufficiently for it to atti-act its heavy armature, the motion of the 

 latter breaks the circuit, which breakage is accompanied with a spark proportionate 

 to the accumulated magnetism, and^ in some measure also to the capacity of the 

 cable, which in this apparatus does not destroy, but rather assists the effect.^ The 

 luminous effect is increased by a slight combustion of mercury, which latter is con- 

 tinually renewed by a circulating pump worked by the armature, by which ar- 

 rangement a good and permanent contact is ensured. 



On a Self-acttnrf Electrostatic Accnmulcttor. 

 By Sir W. Thomson, LL.D., F.R.S. 

 The apparatus described in a recent communication to the Royal Societj', en- 

 titled "On a Self-acting Apparatus for multiplying and maintaining Electric Charges, 

 with applications to illustrate the Voltaic Theory," was exhibited in action. Both 

 Leyden jars being at first discharged as completely as could be done by keeping 

 their outer .and inner coatings connected for several days, they became charged, 

 one positively and the other negatively, through the action of the drops of water, 

 to such a degree, in the course of a few minutes, as to cause the jets of water to 

 scatter over the lips of the receivers. The jars were afterwards repeatedly dis- 

 charged, and the rapid reaccumulation of charges was shown to the Meeting by 

 the scattering of the jets, by electroscopic tests, and by sparks drawn from the in- 

 sulated conductors. 



On a Series of Electrometers for Comparable Measurements through Great 

 Itanrie. By Sir W. Thomson, LL.B., F.R.S. 

 These instruments, which were refen-ed to in Mr. Jenkin's Tieport of the Stand- 

 ards of Electrical Tnits Committee, were exhibited to the Section, and some of 

 them shown in action. ^\. description of them, with drawings, will appear in an 

 appendix to that Report. 



On a U))i form-Electric-Current Accumulator. 

 By Sir W. Thomson, LL.D., F.B.S. 

 Conceive a closed circuit, CTABC, according to the following description : — One 

 portion of it, TA, tangential to a circular disk of conducting material and somewhat 

 longer than the radius ; the continuation, AB, at right angles to this in the plane 

 of the wheel, of a length equal to the radius ; and the completion of the circuit 

 by a fork, BO, extending to an axle bearing the wheel. If all of the wheel were 

 cut away except a portion, CT, from the axle to the point of contact, at the cir- 

 cumference, the circuit would form a simple rectangle, CTAB, except the bifurca- 

 tion of the side 130. Let a fixed magnet be placed so as to give lines of force 

 perpendicidar to the wheel, in the parts of it between C the centre and T thepoint 

 of the circumference touched by the fixed conductor} and let power bo applied to 



