120 ANNUAL OF SCIENTIFIC DISCOVERY. 



greatly increased, and a battery of twelve large jars is said to have 

 been discharged through a space of about three feet. The quantity 

 of the spark, however, is only that of a single jar, and therefore, to 

 pursue experiments satisfactorily, large jars must be used, with an 

 abundant source of electricity from a powerful machine. In order to 

 make the change in the arrangement of the jars, each jar is support- 

 ed in a horizontal position on a vertical spindle, and a slight turn giv- 

 en to each spindle at once brings them from the position they are 

 placed in for charging into the series described. 



ELECTRIC BATTERIES. DISCOVERY IN PLATING. 



AT the late meeting of the British Association Mr. W. S. Ward 

 produced a paper on this subject, and stated that a series of calcula- 

 tions, founded on data, produced to the Chemical Section at Swansea, 

 showed the efficient power of three generally useful forms of battery, 

 known as Smee's, Daniell's, arid Grove's, would be equal when 100 

 pairs of Smee's, 55 pairs of Daniell's, or 34 pairs of Grove's were used, 

 and that the expense of working such batteries, as regards a standard 

 of 60 grains of zinc in each cell per hour, would be about 6d., l^d., and 

 8d., respectively. 



This communication led to some conversation on the economy of 

 the various batteries, and the processes for plating; in the course of 

 which Mr. Shaw and Dr. Percy instanced the magneto-electric ma- 

 chines which are employed at Birmingham for electro-plating, in 

 which the current cost of the motive power viz. a steam-engine 

 to put the magneto-electric machine in action was the only working- 

 cost. Mr. Elkington stated that they had never been induced to 

 abandon the voltaic battery which they employed in their manufactory, 

 finding it more economical than the magneto-electrical machine, of 

 which he was the patentee. He also stated the remarkable fact, that 

 a few drops of the sulphuret of carbon, added to the cyanide of silver, 

 in the decomposing cell, has the property of precipitating the silver 

 perfectly bright, instead of being granulated so dead as it is when 

 thrown down from the solutions ordinarily employed. London Aihe- 

 n&um, Sept. 



INGENIOUS APPLICATION OF ELECTRICITY. 



THE London Athenaum furnishes the following ingenious applica- 

 tion of electricity, by means of which signals are given that indicate 

 the pressure of steam in the boiler of an engine. The invention is 

 by Mr. Arthur Dunn. " Tubes being filled with mercury are made 

 part of a galvanic circuit, and connected with bells as the mercury 

 rises from increasing pressure in the boiler ; the circuit is thus com- 

 pleted, and the bells respectively rung indicate the amount of pres- 

 sure. In this way attention is called to the condition of the steam 

 the moment it exceeds its ordinary and safe working condition." 



