336 ELECTRICITY DURING THE NINETEENTH CENTURY. 



bi'oko in mid ocean and the work ag-ain ceased. The great task was suc- 

 cessfully accomplished in the following year, and the pluck and perti- 

 nacity of those who were staking their capital, if not their reputation for 

 business sagacity, were amply rewarded. Even the lost cable of 1866 

 was found, spliced to a new cable, and completed soon after as a sec- 

 ond working line. The delicate instruments for the working of these 

 long cables were due to the genius of Sir William Thomson, now Lord 

 Kelvin, whose other instruments for electi'ical measurement have for 

 years been a great factor in securing precision both in scientific and 

 pi-actical testing. The number of cables joining thi^ Pjastern and West- 

 ern hemispheres has been increased from time to time, and the open- 

 ing of a new cable is now an ordinary occurrence calling for little or 

 no especial note. 



The introduction of the electric telegraph was followed by the inven- 

 tion of various signaling systems, the most important being the fire- 

 alarm t(4egraph as suggested by Channing and worked out by Farmer. 

 We now, also, have automatic clock systems, in which a master clock 

 controls or gives movement to the hands of distant clock dials by elec- 

 tric currents sent out over the connecting or circuit wires. Automatic 

 electric signals are made when fire breaks out in a building, and alarms 

 are similarly rung when a burglar breaks in. Not only do we have 

 telegraphs which print words and characters — as in the stock " ticker " — 

 but in the form known as the teleautograph, invented by Dr. Elisha 

 Gra}^, the sender writes his message, which writing is at the same time 

 being reproduced at the receiving end of the line. Even pictures or 

 drawings are "wired" by special instruments. The desirability of 

 making one wire connecting two points do a large amount of work, 

 and thus avoiding the addition of new lines, has led to two remarkable 

 developments of telegraphy. In the duplex, quadruplex, and multi- 

 plex systems several messages may at the same time be traversing a 

 single wire line Avithout interference one with the other. In the rapid 

 automatic systems the working capacity of the line is increased by 

 special automatic transmitting machines and rapid recorders, and the 

 electric impulses in the line itself follow each other with great speed. 



Improvement in this field has by no means ceased, and new systems 

 for rapid transmission are yet being worked out. The object is to 

 enlarge the carrying capacity of existing lines connecting large cen- 

 ters of population. The names of Wheatstone, Stearns, Edison, and 

 Delaney are prominent in connection with this work. For use in 

 telegraphy the originally crude forms of voltaic battery — such as Davy 

 used — were replaced b}^ the more perfect types — such as the constant 

 battery of Daniell, the nitric-acid battery of Grove, dating from 1836, 

 and the carbon battery of Bunsen, first brought out in 1842. Such 

 was the power of the Grove and Bunsen batteries that attention was 

 again called to the electric arc and to the possibility of its use for 



