NATIONAL ACADEMY OF SCIENCES. 



alphabet. When these were touched the influence of the batteries 

 was sent through a copper wire and a mark answering to a letter 

 was made a long way off. * * * But long after the telegraphic 

 instruments were perfected it was doubtful whether intelligence 

 could be sent to any considerable distance. It is one thing to send 

 an electric current a few yards and a totally different affair to send 

 it a thousand miles. Experiments which had been made under the 

 auspices of the Russian government by Professor Jacobi, of the 

 University of Dorpat, had led to the inference that the law of the 

 conducting power of wires, originally discovered in Germany, was 

 correct ; and, in addition, a corroborative memoir had been read by 

 Lenz before the Imperial Academy of Sciences at St. Petersburg. 

 At this time so little was known in England as regards this impor- 

 tant point, that some of the most eminent natural philosophers con- 

 nected with universities there embraced the opposite view. I may 

 not be able to make the precise point in dispute clear; it was this : 

 A current passing through a certain length of wire suffers a certain 

 amount of loss. If it should go through a wire a thousand times 

 as long will the loss be a thousand times as great ? The Russians 

 said yes ; the English said no. If the former was the case it was 

 universally concluded that the electric telegraph would not be prac- 

 ticable for any considerable distance. A series of experiments was 

 made in the University of New York which established beyond all 

 question the truth of the Russian view. But at that time the higher 

 mathematics were cultivated in our laboratory, as well as mere ex- 

 perimenting ; and on submitting the results to such a mathematical 

 discussion the paradoxical conclusion was brought out that it is a 

 necessary consequence of that law that after a certain length of 

 wire has been used the losses become imperceptible. Encouraged 

 by this, a party of gentlemen went with the inventor of the telegraph 

 to a rope-walk near Bloomingdale, one summer morning, and there 

 tested the truth of these conclusions on lengths of wire varying from 

 one to some hundreds of miles. The losses of the currents were 

 measured by the quantity of gas set free in the decomposition of 

 water. The result was completely successful, and telegraphing for 

 any distance became an established certainty." 



The part which he took in the evolution of photography he thus 

 describes : ** When the French government, in 1839, purchased of 

 Daguerre his invention of photogenic drawing, its applications were 

 very limited. The process was adapted to interiors, statuary, and 



378 



