NOVEMBKR 23, 1883.] 



SCIENCE. 



675 



The cost of the lamps is one dollar each ; ami, 

 at the i)resent rate of consumption from all 

 causes, the annual expenditure will be 5G lamps. 

 The dynamo is run about 2,190 hours per j-ear 

 (about six hours per day), with an average of 

 about 47i lamps in circuit, so that the annual 

 lamp-hours would be about 104,025 (2190 x 

 47.5). Thus it appears that our lamps will, 

 at present consumption, last us in the neigh- 

 borhood of 1,857 (i"ip5^) hours e.ach. 



Description of lamps. 



In event of a short circuit through a good 

 conductor, between the wires there would be 

 instantly generated heat of such intensity that 

 the wires would melt, and perhaps the arma- 

 ture also. This heat would in all probability 

 set fire to the wood-work along the line of the 

 wire. To prevent this. Edison has devised his 

 cut-out block, or safety-catch, — a neat device 

 for placing a short piece of alloy in the circuit, 

 which, at 400^ F., will melt, and open the cir- 



cuit. When this happens, all the lamps on 

 the branch circuit fed through that cut-out 

 ^ill be immediately extinguished ; and. though 

 one is left in darkness at that point, he is re- 



warded Ijy a consciousness of greater mischief 

 having been prevented. Fig. 15 represents a 

 double pole cut-out block, a front and back 

 view of the cut-out plug, and a binding-screw. 

 Fig. 1 6 shows a back view of the same cut-out 

 block, and a section through a cut-out plug. 

 The fusible alloy is contained iii the plug, and 



is utilized as a solder to unite the two poles of 

 the plug. The plug is made similar to the 

 bottom of a lamp, and the block-socket is 

 similar to a lamp-socket. The wires are held 

 by the binding-screws, and the current passes 

 through the metal of the block and plug. 

 These cut-outs are placed on each of the main 

 circuits, near the dynamo, and on each branch 

 circuit, and always in convenient positions. 

 The alloy in the plug is the only jtart destroyed 

 by a short circuit, and it is only a minute's 

 work to substitute a new plug. 



( To be <:ontinued.) 



REPORT OF THE GERMAN CHOLERA 

 COMMIS^SION.^ 

 Whex the commission arrived in Eyypt, the chol- 

 era epidemic had already begun to decline, so that 

 we could not e.Kpect to obtain all tlie material neces- 

 sary for carrying out our examinations. Besides, 

 since the termination of an epidemic is the least 

 suitable time for etiological researches, our origi- 

 nal plan was to make such preliminary studies as we 

 could in Egypt, and then check our results, as soon as 

 the epidemic h,id reached Syria, by further investiga- 



* Kcport to Minister von BBttlcher, secretary of state for the 

 interior. Ity Dr. Koch, Vrom Ihc A'olnim-hf eeitung of Oct. 1.'. 



