22 REPORT—1840., 
currents, he has founded upon it a new method of measuring these 
currents, and of determining the different elements or constants, which 
enter into the analytical expressions, and on which depends the action 
of any galvanic combination. It is principally to the measure of the 
electromotive force, by those means, that Mr. Wheatstone has directed 
his attention; and he has shown me, in his unpublished papers, very 
valuable results which he has obtained by this method. 
While these purely theoretical researches were in progress, I did 
not fail myself to enter directly upon the question of the practical ap- 
plication of electro-magnetism. Unfortunately, I cannot here give the 
details either of the experiments which I have made upon a very large 
scale, or of the machines and apparatus of various kinds which I have 
constructed. The necessity of multiplying the facts or tangible results 
—a necessity the more urgent, because the practical applications of 
this force increased so very rapidly—this necessity, I say, has not al- 
lowed me time or leisure to digest and arrange them. I can only here 
express my readiness to afford any explanation of the details which 
may be desired. I will, however, particularly notice the satisfactory 
results of the experiments made last year with a boat of twenty-eight 
feet in length and seven and a half feet in width, drawing 2% feet of 
water, and carrying fourteen individuals, which was propelled upon the 
Neva at the rate of about three English miles in the hour. The 
machine, which occupied very little space, was set in motion by a bat- 
tery of sixty-four pairs of platina plates, each having thirty-six square 
inches of surface, and charged according to the plan of Mr. Grove, 
with nitric and diluted sulphuric acid. Although these results may 
perhaps not satisfy the exaggerated expectations of some persons, it is 
to be remembered, that in the first year, namely, in 1838, this boat 
being put in motion by the same machine, and employing 320 pairs of 
plates, each of thirty-six square inches, and charged with sulphate of 
copper, only half this velocity was obtained. This enormous battery 
occupied considerable space, and the manipulation and the management 
of it was very troublesome. The judicious changes made in the dis- 
tribution of the rods, in the construction of the commutator, and lastly, 
in the principles of the voltaic battery, have led to the successful result 
of the following year, 1839. We have gone thus on the Neva more 
than once, and during the whole day, partly with and partly against 
the stream, with a party of twelve or fourteen persons, and with a ve- 
locity not much less than that of the first invented steam-boat. I 
believe that more cannot be expected from a mechanical force, whose 
existence has only been known since 1834, when I made the first ex- 
periment at Koénigsberg, in Prussia, and only succeeded in lifting a 
weight of about twenty ounces, by even this electro-magnetic power. 
I must, on the present occasion, confess frankly and without 
reserve, that hitherto the construction of electro-magnetic machines 
has been regulated in a great measure by mere trials; that even the 
machines constructed according to the indisputable laws established 
with regard to the statical effects of electro-magnets, have been found 
ineficient, as soon as we came to deal with motion. Being always 
