THE TECHNOLOGIST. [July 1, 1865. 



540 THE FROGRESS OF 



double faith in a thing when we are able to give it a name. The re- 

 cognised and titled electricity made rapid progress. The lump of amber 

 was changed for a fragment of sulphur, which soon grew into a globe, 

 and was by-and-by replaced by a glass sphere, a cylinder, or a plate, 

 whirled rapidly, and constituting an electrical machine. To make this 

 advance took men an whole century, which we may call the epoch of 

 the electrical machine. By the beginning of the eighteenth century, 

 however, they knew well how to produce electricity but not how to 

 manage it. 



In little more than a quarter of a century they had learned that some 

 bodies conduct, and others do not conduct electricity, and were in posses- 

 sion of the essential halves of an electrical highway or telegraphic line, 

 namely, conductors free through half their length, and insulated through 

 the other half by non-conductors. 



Four years before the half-century ( 1745), the Leydenjar was stumbled 

 on. It was literally an electrical condenser, and did as much to en- 

 hance the power of the friction machine, as Watt's steam condenser 

 did to enlarge that of the steam-engine. 



Provided with the Ley den jar, the next two important telegraphic dis- 

 coveries were speedily made : the one that electricity traverses a metallic 

 wire with inconceivable rapidity ; the other that it travels with equal 

 celerity through earth or water. Here, then, were two-thirds of the tele- 

 graph supplied ; the message-sender was there, and so was the message • 

 carrier. Why did no one think of providing a message-receiver, the 

 easiest part of the business 1 In truth men did provide one, but his 

 office was a sinecure. Scarcely a message reached him, and the few that 

 did were too confused to admit of interpretation. 



The fault lay with the sender. Friction electricity is so brief in 

 duration, and so intense and impetuous, that it cannot be induced to 

 take a long journey. The best conductors in their best state of insula- 

 tion are still unwelcome to it. If there is the least obstacle in any part 

 of its path, it turns off, as it were, at a side station, and returns by the 

 shortest route with its message undelivered. 



No improvement was made for half a century on the conductors, and 

 electrical telegraphy remained at a stand-still till the beginning of the 

 nineteenth century. It should have dated from exactly the second 

 centenary of the naming of electricity ; for in 1800 the voltaic battery, 

 already some years in use, was ascertained to produce chemical decom- 

 position, and in that instrument we have a machine producing a con- 

 tinuous stream of electricity far less impetuous and reluctant to travel 

 than the electricity of the friction machine, and still more able by its 

 decomposing power to produce record signals. A . voltaic battery as 

 message-sender, wires as message-carriers, and a ribbon of chemical 

 paper on which the current carried by the wires prints signals in 

 Prussian blue, as message-receiver, is one of the best and most common 

 arrangements now in use. 



