284 
POPULAR SCIENCE REVIEW. 
‘ The means of storing and re-storing mechanical energy form the aspira- 
tion not only of Sir William, but of every educated mechanic. It is, how- 
ever, a question of degree — of the amount of energy stored as compared with 
the weight of the reservoir, the standard of comparison being coal and corn. 
Looked at in this way, one cannot hut ask whether, if this form of storage is 
to he the realization of our aspirations, it is not completely disappointing. 
Large numbers are apt to create a wrong impression until we inquire what 
is the unit. Eleven million foot pounds of energy is what is stored in 1 lh. 
of ordinary coal. So that in this box, weighing 75 lbs. there was just as 
much energy as in oz. of coal, which might have been brought from Paris, 
or anywhere else, in a waistcoat pocket, or have been sent by letter. 
‘ When we come to the question of the actual conveyance of energy for 
mechanical purposes, this view is of fundamental importance. The weight 
of the same amount of energy in the new form is 800 times greater than the 
equivalent amount of coal; and as a matter of economy, supposing that 
energy in this form might be had at a certain spot, and no capital were re- 
quired for its conversion or storage, and that the energy were directly appli- 
cable, it could not be carried ten miles, that is to say, such energy cannot be 
economically useful ten miles from its source, although coal had to be carried 
one hundred miles to the spot. This limit, in truth, falls far short of what 
has been already attained by other means. By wire ropes and by compressed 
air or steam energy may be economically transmitted from ten to twenty 
miles. So that if this is the utmost of what is to be done by means of the 
storage of electricity, this discovery adds another door to those which are 
hopelessly closed against the possibility of finding in Niagara or other water- 
power a substitute for our coal, even when the object is motive power, and 
much more for that purpose for which five-sixths of our coal is used — the 
production of heat. 
1 It is very important that the people of this country should not shut their 
eyes to the fact that so far from there being a greater prospect of the solu- 
tion of the problem than when, about twenty years ago, Prof. Jevons raised 
the alarm, the prospect is now much smaller. In the meantime the capa- 
bilities of steel ropes, fluids in pipes, and electricity along conductors, have 
been not only investigated, but practically tested and found altogether want- 
ing. And now, it would seem, that the storage of electricity must be added 
to the list. ( Osborne Reynolds. 
‘ Owens College , June 9.’ 
‘ Sir, — Your leading article in the Times of yesterday on the storage of 
electricity alludes to my having spoken of Niagara as the natural and proper 
chief motor for the whole of the North American Continent. I value the 
allusion too much to let it pass without pointing out that the credit of 
originating the idea and teaching how it is to be practically realized by the 
electric transmission of energy is due to Mr. C. W. Siemens, who spoke first, 
I believe, on the subject, in his Presidential Address to the Iron and Steel 
Institute in March, 1877. I myself spoke on the subject in support of Mr. 
Siemens’s views at the Institution of Civil Engineers a year later. In May, 
1879, in answer to questions put to me by the Select Committee of the 
House of Commons on Electric Lighting, I gave an estimate of the quantity 
