(858.) 
(859.) 
The earth- 
circuit. 
986 
for general adoption in a convenient form, is a matter 
which we need not here decide. The three indepen- 
dent inventors (I name them alphabetically) are Mr 
Morse of the United States, M. Steinheil of Munich, 
and Mr Wheatstone of London. The telegraph of 
the two last resembles in principle Oersted’s and 
Gauss’s; that of the first is entirely original, and con- 
sists in making a ribbon of paper move by clockwork, 
whilst interrupted marks are impressed upon it by 
a pen or stamp of some kind brought in contact with 
the ribbon by the attraction of a temporary magnet, 
which is excited by the circulation of the telegraphic 
current of electricity. In the telegraphs of MM. 
Wheatstone and Steinheil the needle moves only to 
the right or left ; and by the combination of a certain 
number of right and left motions, either with one or 
with two independent needles acted on at once by 
distinct currents, the alphabet is easily, though some- 
what tediously constructed. Such, however, is the 
dexterity which practice gives, that forty or even 
more of such complex signals are transmitted and 
registered per minute! 
It has already been said that we claim the exclu- 
sive invention of the electric telegraph for no one in- 
dividual. But of the several inventors none pro- 
bably has shown such perseverance and skill in over- 
coming difficulties as Mr Wheatstone.? His telegraph 
accordingly was in general use in England before M. 
Steinheil was able to obtain a similar success in 
Germany. The telegraphs of Mr Morse are naturally 
preferred in America, and they have this inestimable 
advantage, that they preserve a permanent record of 
the despatches which they convey. 
There is one circumstance connected with the elec- 
tric telegraph deserving of particular notice—I mean 
the apparently infinite conducting power of the earth 
when made to act as the vehicle of the return current. 
Setting all theory aside, it is an unquestionable fact, 
that if a telegraphic communication be made, sup- 
pose from London to Brighton, by means of a wire 
going thither, passing through a galvanometer, and 
then returning, the force of the current shown by 
the galvanometer at Brighton will be almost ea- 
actly doubled, if, instead of the return wire, we 
establish a good communication between the end of 
the conducting wire and the mass of the earth at 
Brighton. The whole resistance of the return wire 
is at once dispensed with ! This fact was more than 
suspected by the ingenious M. Steinheil in 1838; 
but, from some cause or other, it obtained little 
publicity ; nor does the author appear to have ex- 
erted himself to remove the reasonable prejudices 
MATHEMATICAL AND PHYSICAL SCIENCE. 
[Diss. VI. 
with which so singular a paradox was naturally re- 
ceived. A most ingenious artist, Mr Bain, estab- 
lished for himself the principle, and proclaimed its 
application somewhat later; and in 1843, perhaps 
the first entirely convincing experiments were made 
by M. Matteucci at Pisa. From this time the double 
wire required to move the needle telegraph was 
reduced to a single one. The explanation of this 
curious fact appears to be,—not that the electricity 
is conducted back by the earth to its origin at the 
battery,—but that the molecular disturbance po- 
larly communicated along the conducting wire to its. 
farther end being effectually relieved by perfect com- 
munication with a vast reservoir of neutral electri- 
city like the earth, conduction proceeds in an unin- 
terrupted manner, and to an unlimited extent. 
Of submarine telegraphs, it is sufficient to state 860.) 
that the isolation is obtained by inserting the eon- Submarine 
ducting wires in a mass of gutta percha, and that *!¢8"P)- 
the first on a considerable scale was sunk between 
Dover and Cape Gris Nez, on the French coast, in 
August 1851. 
The applications of electricity tothe measurement 861.) 
of time are so numerous, that I can only refer ge- 
nerally to the principal contrivances. 
1, The simple electric clock of Mr Bain derives its _(862.) 
maintaining power from two large plates of copper Hiectrie 
and zine (or more simply zine and charcoal) sunk in © °°” 
the earth, which affords for a very long time a con- 
tinuous supply of voltaic electricity. The current is 
conveyed into the bob of the pendulum, where it 
traverses a long coil of wire; and as the pendulun 
oscillates, the current (by a simple shifting contriv- 
ance) is reversed at each vibration, A stationary 
bar-magnet is placed so that when the pendulum 
moves, the voltaic coil of the bob embraces the mag- 
net, and the direction of the current is such as by 
the electro-magnetic reaction to strengthen and main- 
tain the vibratory movement, which is by this means 
perpetuated. 
2. Sympathetic clocks.—By means similar to those 863.) 
just explained, one standard clock anyhow regulated Sympathe- 
may, by means of magneto-electrie currents, convey “ —_ 
absolutely isochronous movements to any number of 
affiliated clocks at any distance. Probably the first 
application of the kind was made by M. Steinheil. 
3. American electric-registration clocks,—Mr (864.) 
Locke proposed to register the instant of an event American 
oceurring in the following way: A ribbon of Scletre: 
paper being put in uniform motion, as in Morse’s tion clocks. 
telegraph, a dot is imprinted on it every second by 
1 Occasionally 18 or 20 words per minute have been telegraphed. 
* I ought to mention that the practical introduction of the electric telegraph in England is in no small degree due to the 
energy of Mr Fothergill Cooke, joint patentee with Mr Wheatstone for the invention. 
The question of the respective shares of 
these gentlemen in the merit of telegraphic communication was submitted, in 1841, to the arbitration of Sir Marc Brunel and 
the late Mr Daniell, the result of which appears to leave the preponderance of merit in some respects ambiguous ; neverthe- 
less, in a history of Science, Mr Wheatstone is clearly entitled to the pre-eminent place. Several pamphlets have also been sub- 
sequently published by the parties. It is significant that Mr Cooke admits having borrowed his idea from becoming acquainted, 
at Heidelberg, in March 1836, with Gauss’s experiments. 
