156 ANNUAL OF SCIENTIFIC DISCOVERY. 



adopt a special electric fluid to explain the electric phenomena, 

 as there exists to adopt a special sonorous fluid to explain the 

 acoustic phenomena. — Scientific American. 



SUBSTITUTE FOR COPPER IN THE DANIELLS BATTERY. 



Few persons, in experimenting upon voltaic combinations, ever 

 consider economy in their construction, and exi)eriments which 

 tend to cheapen their first cost should be made public. 



An expensive part of the Daniells battery is the copper plate, 

 the cost of which can be reduced two-thirds, in the following 

 UKinner : — 



Procure sheets of the ordinary sheet tin of commerce, brighten 

 and plunge into a very weak copper plating solution, in connec- 

 tion with a voltaic battery of very low quantity. In 15 to 18 

 hours a tenacious film \)f copper will have been deposited upon 

 the tin, and the plate can then be bent in shape suitable for a 

 Uaniells battery. — Telegraph. 



THE " WAVE " TIME OF THE ELECTRIC TELEGRAPH. 



The Boston " Traveller" gives the following oflicial figures from 



tlie records at Harvard College : "It was proposed to begin with 

 a comparatively short loop, extending from Cambridge to Buflalo 

 and back, and then to extend the loo])s successivel}' to Chicago, 

 Omaha, Salt Lake, Virginia City, and finally to San Francisco. 

 The plan was put into execution on the nights of February 28th 

 and March 7th, and in both instances the results were extremely 

 successful. It was quite fascinating to stand before two instru- 

 ments, a few inches apart, and to see and hear a signal made upon 

 one, repeated upon the other in a fraction of a second, after hav- 

 ing traversed a distance of over 7,000 miles. 



" Below is given a table which shows the time, to hundredths 

 of seconds, occupied l)y a signal passing from Camln'idge to each 

 of the stations and back. The numbers of repeaters in the cir- 

 cuits are also given : — 



''time of transmission from CAMBRIDGE. 



Seconds. 



To Buffalo and return, 0.10 1 repeater. 



To Chicago and return, 0.20 3 " 



To Omaha and return, 0.33 6 " 



To Salt Lake and return, 0.:)4 9 " 



To Virginia City and return, .... 0.70 11 " 



To San Francisco and return, .... 0.74 13 " 



" The actual time of transmission from Cambridjire to San Fran- 

 CISCO and back does not probably exceed three-tenths of a sec- 

 ond : tho ' armature times* of the 13 repeaters, in all probability, 

 amount to four or five tenths of a second." 



