160 ANNUAL OF SCIENTIFIC DISCOVERY. 



this little channel can accommodate, is constantly running through it from 

 pole to pole, making it very hot, but it is kept from getting red-hot by the 

 water in which it is immersed. The water is sustained at a boiling tempe- 

 rature to the relief of the fine filament of heated metal. When contact is 

 made or broken by the key, this subsidiary contrivance being in operation, 

 the main body of the current passes through the key, and the slight leaking 

 still goes on through the platinum wire, but no spark appears. The con- 

 tact is entirely lightless and quiet. The spark is absorbed in the mainte- 

 nance of the leak. There is a slight increased consumption of zinc in the 

 battery on account of this leak. The battery is always in subdued opera- 

 tion, instead of being in absolute rest between the successive contacts made 

 for the transmission of the currents. 



This battery, it is to be understood, is not to be used primarily in ope- 

 rating the telegraph, but for exerting a magneto-electric current, which will 

 be subsequently used for signalizing. 



IMPROVEMENTS IN GALVANIC BATTERIES. 



Kuhns's Battery. Kuhns of Bavaria, has found by experiment, that in 

 a battery the ratio of the zinc surface to that of copper depends, in a great 

 measure, on the quality of both substances, and that to produce economic- 

 ally the greatest result, the relative sizes have to be found experimentally in 

 each case. For this reason he uses amalgamated wires of zinc, instead of the 

 usual cylinders, and increases progressively the quantity of it till the maxi- 

 mum strength of current is reached. The same inventor has also discovered 

 that, when the battery is heated to 120 Fahrenheit, the current produced is 

 stronger than at any other temperature, and he has invented a battery which 

 may be heated easily. It consists of a cast-iron box divided into two por- 

 tions by a false bottom. The elements are placed side by side in the upper 

 compartment in a bed of sand. In the lower compartment is an alcohol 

 lamp. The sand gets uniformly heated, and keeps the elements at the 

 proper temperature. After a little practice any person will find how the 

 wick of the lamp has to be trimmed to heat the sand up to 120, and keep 

 it at that temperature. This process is used in most Parisian coffee-houses 

 to keep coffee as warm as possible without spoiling it by boiling. It is prob- 

 able that the sti-ength of current is proportional to the quantity of chemicals 

 used up, whatever be the process for producing the same. Hence the ques- 

 tion, Will warming the battery increase the strength of the current, more 

 economically in cost of apparatus, expense of chemicals, labor and risk of 

 getting out of order, than making it larger by adding more of the elements ? 



Doat's New Buttery, icith a constant Current. In this battery the zinc is 

 replaced by mercury, the acidulated water by iodide of potassium ; the 

 nitric acid, or sulphate of copper of the batteries with two liquids, by iodine 

 dissolved in the iodide of potassium, and, which put in excess in the solid 

 state, serves to maintain constant action. Carbon is employed as the nega- 

 tive pole. A square trough, of gutta percha, contains the mercury and the 

 alkaline iodide. The carbon and the iodized iodide are put into a square 



