Manchester Mevwirs, Vol. Ixiii. (1920) No.'h 3 



This type of armature (See J^/. I., Fig. i) Wilde adopted, and he 

 described the details of his machine in a paper with the title, " Ex- 

 perimental Researches in Magnetism and Electricity," which was 

 communicated to the Royal Society by Faraday in 1866. The 

 magneto is shown in the upper part of Fig. 2. Two blocks of 

 cast iron D and D, and two pieces of brass of the same length 

 were fixed together with brass bolts, so that a hollow cylinder — 

 which he termed the "magnet cylinder" — was formed, having 

 a hole of is/g in. in diameter. The armature core was of cast 

 iron, on which was wound 163 feet of copper wire 0-03 in. 

 diameter. The U-shaped steel magnets A were 8 in. long, i in. 

 wide, and \ in. thick. Each magnet was about i lb. in weight, and 

 able to support 10 lbs. The armature was rotated at 3,000 

 revolutions per minute by the belt M. Experiments were made 

 ^vith a varying number of magnets, and what Wilde called 

 " the quantity of electricity produced " was measured by a 

 tangent galvanometer (see Appendix A). This magneto was 

 used to excite electro-magnets, the largest having limbs 2 ft. 

 long and 31/2 in. diameter. With four steel magnets in position 

 on the magneto, 1,088 lbs. was required to detach the keeper 

 of the electro-magnet, this being 27 times the weight that the 

 combined, four magnets were able to support. This he regarded 

 as a paradoxical phenomenon, which appeared to him to be a 

 new principle in electro-magnetism. 



The second part of the 1866 Royal Society paper is especially 

 interesting and important in connection with the history of 

 electrical generators. It relates to " A new and powerful gene- 

 rator of dynamic electricity," and describes the construction of 

 a new magneto and of three machines with electro-magnets. 

 The magneto was fixed to the top of the electro-magnetic 

 machine, and its electro-magnet B (see Fig. 2) was excited by 

 the current from the magneto. The armature of the electro- 

 magnetic machine was driven by the belt M^. Further details of 

 the four machines are given in Appendix B. They are classified 

 according to the size of the bore of the magnet cylinder, which 

 in the three electro-magnetic machines was 2^, 5 and 10 ins. 

 respectively. The lo-in. machine was provided with two arma- 

 tures, one for "intensity" and the other for "quantity." With 

 •this large machine, using the intensity armature, Wilde was 

 enabled to produce a strong arc light. He used a Foucault arc 

 lamp provided with a parabolic reflector 20 ins. in diameter. 

 This was placed on the top of his works, and cast shadows of 

 the flames of the street lamps a quarter-of-a-mile away on the 

 neighbouring walls. He says: "When viewed from that distance, 

 the light was a very magnificent object to behold, the rays pro- 

 ceeding from the reflector having all the rich efifulgence of 

 sunshine." A piece of photo paper exposed to the light for 20 

 seconds at a distance of 2 feet from the light was darkened as 



