;.C,0 KANSAS CITY REVIEW OF SCIENCE. 



Thomson. Prof. Osborne Reynolds, of Owens College, Manchester, for instance, 

 points out that, after all, 1,000,000 foot-pounds is a very small matter, being in 

 fact just as much " energy" as is contained in i^ ounces of coal. Coal, indeed, 

 is to be our standard, according to Mr. Reynolds, and he predicts the utter failure 

 of the plan for storing electricity. Professor Ayrton also comes forward as a 

 critic, albeit one of a milder type. He admits the truth of the statement that i^ 

 ounces of coal contams 1,000,000 foot-pounds of energy, but he very pertinently 

 asks how that force is to be extracted to its full extent. As a matter of fact it is 

 impossible to attain that result, no known engine being capable of working with 

 so minute a quantity of fuel. This is exactly where the difference lies. The coal 

 may contain the power, but it is all latent, and not available without the aid of a 

 much greater force than its own, whereas the electricity is all immediately availa- 

 ble, and can be used wholly or partially at will. Besides this the coal once used 

 is done with, whereas the Faure accumulator can be stored anew, and drawn upon 

 as required. This is an essential distinction, and would seem to show that the 

 criticism of Professor Reynolds is wholly beside the mark. Professor Ayrton 

 intimates that himself and Mr. Perry are making attempts to convert at a low 

 temperature the energy in coal into electric energy, and Sir William Thomson 

 admits that if carbon could be extracted in this manner the result would be anal- 

 oo-ous to what is done by the Faure accumulator. So far, however, M. Faure 

 alone has achieved success, and it is to his apparatus, therefore, that we must 

 look for the speedy, practical solution of one of the great problems of the day. 

 — Ironmonger. 



CORRESPONDENCE. 



NOTES FROM "CORRESPONDENCE SCIENTIFIQUE." 



Paris, July 12th. 



The " Correspondence Scientifique " is a lithographed facsimile of the arti- 

 cles on scientific subjects prepared for early information of the press and of indi- 

 viduals, by Chas. Varey, scientific editor of LaPresse, a leading journal of Paris. 



The last number received, dated the 12th ultme, has articles under the fol- 

 lowing headings: " Optical Telegraph," from which it appears that the French 

 military authorities have only recently brought into practical use, the Signal Sys- 

 tem adopted, perfected and most successfully used in the Union Army, through 

 the latter part of the civil war. 



" Hygienic Properties of Electric Illumination." An interesting article of 

 which a translation is given below. 



