348 



TRANSACTIONS OF THE AMERICAN INSTITUTE. 



for batteries formerly'- expended. The following is from tlic report of the 

 Engineer of the American Telegraph Company, of trials made of this 

 battery : 



" It was subjected to a competition with three other powerful battery 

 combinations, during GO days, alternating it by using on different lines, 

 each about 250 miles. Estimate of amount of labor, weights of acici, zinc 

 and mercury consumed, and galvauometric tests were daily made to estab- 

 lish uniformity of power. 



The experiments, embracing altogether the use of about 320 cells, and 

 thoroughly carried out under the direction of the engineer of the American 

 Telegrapli Co., resulted in the following figures: 



The original form of the battei'y is still preserved, the only change being 

 in the mode of making the platina connections. Imitators have endeavored 

 to nuike up the battery by driving copper wires into the carbon, or by 

 using a clamp covered with lead, but these connections all became oxidized 

 and worthless, and have been abandoned. Besides the saving of expense, 

 the abandonment of nitric acid has preserved the health of operators, and 

 prevented the fatal corrosion of connecting wires. 



On motion adjourned to Thursday evening next. 



Amekican Institute Polytechnic Association, ) 



September 15, 1864. ) 



Chairman, Prof. S. D. Tillman; Secretary, B. Grarvey. 



During the hour devoted to the examination of new inventions and dis- 



. I . . . 



coveries, the Chairman presented the following interesting items of scientific 



nev;s; 



Elongation of Electro-Magnets. 



A bar of pure wrought iron, within a helix of insulated copper wire, is 

 very slightly elongated while a current of electricity is passing through the 

 wire. The instant the current is broken, the bar returns to its original 

 length. The difference in the length of the bar is too small to be perceived 

 by the eye, but is made apparent by connecting the bar with a system of 

 levers. Prof. Tyndal, of the Royal Institution, London, has lately arranged 

 an apparatus by which this singular phenomenon can be witnessed by a 

 largo assembly. To the end of the lever of gi-eatest .action he fastens a 

 small mirror. A powerful light is so placed that a portion of it will be 

 thrown by the mirror upon an elevated white surface some twenty feet in 

 diameter. The motion of the light upon it indicates the action of the bar 

 when the circuit is closed or broken. 



