P OP UL AR MIS CELL ANY. 



285 



crowded out of its original position between 

 the marginal bones of the second or epipo- 

 dial series into the third or mesopodial se- 

 ries. In icthyosaurus, the intermedium is 

 not entirely excluded from the third row ; 

 in plesiosaurus and all other reptiles the 

 process is essentially completed. In some 

 amphibians, the bone still separates the 

 lower end of the two specialized bones 

 above it. Sauranodon marks an earlier and 

 most interesting stage in the differentiation, 

 and indicates how the transition was accom- 

 plished. Some of the amphibians retain 

 remnants of a sixth digit, and icthyosaurus 

 often presents traces that represent lost 

 digits ; but with these exceptions the normal 

 number of five digits is not exceeded in any 

 other air-breathing reptile than sauranodon. 



To pierce Glass with the Electric Spark. 



In the usual process of piercing glass with 

 the electric spark when the glass is thick, 

 one of the wires has to be inserted in a bed 

 of insulating resin, quite thick, and which 



has itself to be melted upon the plate of 

 glass. The operation, involving the use of 

 heat, is inconveniently long ; and, besides, 

 the trouble of cleaning the glass of the 

 resin has to be gone through after the hole 

 is made. The process described below by 

 M. Fages, architect of the city of Narbonne, 

 is easy of application, and requires only a 

 few minutes for preparation and execution. 

 The apparatus is so simple that any one 

 can construct it for himself, and it may be 

 used for an indefinite number of operations. 

 The cut represents it in vertical section. 

 It consists of 1. A rectangular plate, A, of 

 hardened, black India-rubber, which should 

 be, for a coil giving a spark of four inches, 

 not less than six inches long and four inches 

 wide; 2. A brass wire, B, the bent point 

 of which, C, screwed or pushed into the 

 India-rubber plate, rises even with its top. 

 To use the apparatus, we lay it horizon- 

 tally on a table, and put the brass thread 

 B in connection with one of the poles of 

 the magnetic coil ; then pour some drops of 



w. 



B 



j^m^_ -__\ZZT- s , - ) \ 



olive or other oil on the India-rubber plate 

 above the point C, and put upon it the plate 

 of glass D, which is to be pierced, taking 

 care that no bubbles of air are inclosed. 

 The oil causes the insulation of the point C. 

 This done, connect the wire E with the other 

 pole of the coil and produce the spark. It 

 is very easy, by moving the glass along, to 

 make a number of holes as close to each 

 other as may be desired. The only precau- 

 tion necessary is to have the India-rubber 

 plate large enough so large that it will not 

 be possible for the spark to jump between 

 the wires by following the routes indicated 

 by the dotted lines. 



An Electrical Railway. Mr. Werner 

 Siemens exhibited an electrical railway at 

 the recent exposition in Berlin, with which 



he attained a fair degree of success in trans- 

 mitting electrical power to a distance, and 

 applying it to the movement of carriages. 

 This apparatus consists of a dynamo-elec- 

 tric machine fixed in the station supplying 

 force to a second machine placed on a loco- 

 motive-carriage and connected with it by the 

 rails of the track and a third rail which is in- 

 sulated in the middle of the track. The elec- 

 trical current is transmitted from the gen- 

 erating machine to the locomotive through 

 the middle rail, and is returned through the 

 wheels and the rails of the track. The car- 

 riages to be drawn by the locomotive are all 

 electrically connected with it, so that com- 

 munication is established through all the 

 wheels. The train exhibited by Mr. Sie- 

 mens consisted of the locomotive and three 

 carriages with seats for six persons each. 



