286 Chronicles of Science. [April, 



trary, that the action of the platinum does not take place except on 

 the gases already below, and that the gas receivers should only be 

 considered as reservoirs to maintain in a state of saturation the solu- 

 tions they cover. The electro-motive force of the gas-couple varies 

 curiously with the state of the platinum wire. Its action is 

 increased, as JUL Matteucci remarked, by heating the elements in 

 the flame of a spirit-lamp some instants before employing it. In 

 the most favourable conditions, the electro -motive force of the gas- 

 couple constructed with platinum wires not platinized scarcely 

 exceeds 155, taking as unity the electro-motive force of a thermo- 

 electric couple of bismuth and copper, the two solderings of which 

 are maintained at the temperature of 0° and 100' C. The electro- 

 motive force of a Darnell's couple is represented by 193, and that 

 of Yolta by 178, at the moment of being set to work. 



An automatic electro-chemical method of electric transmission 

 of despatches has been invented by MM. J. Yavin and Gr. Fribourg. 

 It consists in the distribution of the current through as many short 

 and isolated small wires as there are signals to be transmitted, 

 whilst employing only one wire on the main line. Each of these 

 small isolated wires communicates on the one hand with a metallic 

 plate of a particular form fixed in gutta-percha, and on the other 

 hand with a metallic division of a disc, which is equally formed 

 of an insulating substance. A group of eleven of these small 

 laminae form a sort of character which will give all the letters of 

 the alphabet by the suppression of certain portions of the funda- 

 mental form. Xow, supposing rows of these compound characters 

 to be placed on a sheet of prepared paper of a metallic nature, the 

 words of the telegram to be sent are written on them with isolating 

 ink, leaving the other parts of the small " stereotyped " blocks un- 

 touched. The consequence is that the current is intercepted at 

 every point touched by the ink, and a letter is imprinted on the 

 prepared paper at the other end of the line where the telegram is 

 to be received. The process by which all these several currents are 

 sent along the one main wire and then made to separate at the end 

 and pass into their respective small wires, is not at all clear in the 

 authors' description. 



Lightning-protectors for telegraphic lines have been in use 

 for many years ; an improvement lately brought out consists of two 

 smooth brass plates from 3- 87 to 4*65 square inches, placed one 

 above the other, and separated by a sheet of paper; one of the 

 metal plates is in connection with the line, the other communicates 

 with the earth. As soon as a rather strong tension occurs on the 

 line, sparks pass from one plate to the other, perforating the paper, 

 and the electricity passes into the earth instead of along the 

 line, disarranging the instruments. M. Guillemin proposes to 



