ELECTRICAL SIGNALLING AND THE SIPHON RECORDER. 361 
drew sparks from an electric machine standing by. Of coarse 
she told her husband ; and, strangely enough, six years after 
he noticed a similar effect in some frogs’ limbs which hung by a 
copper rod from an iron balustrade, independent of the agency 
of the electrical machine. Judging from subsequent experi- 
ments, he explained the last phenomenon by supposing a spe- 
cific kind of electricity to reside in the nerves, and this, flowing 
through the metals into the muscles, threw the latter into con- 
vulsions. But to Volta, professor of physics at Pavia, we are 
indebted for the true explanation that the two metals (iron and 
copper) of the skewer and balustrade were the real electro- 
moters ; and, in proof of this, Volta constructed the progenitor 
of a great race of important agents of civilisation — the zinc and 
copper “pile.” 
It was not a difficult thing to insulate or confine the electricity 
of the voltaic pile, and the progress of electric telegraphy was 
thenceforth rapid, but not until Professor Oersted of Copen- 
hagen, in 1820, discovered that a current of electricity deflected 
a magnetic needle in its neighbourhood, and Schweiger of 
Halle applied the fact, did the heyday of telegraphy dawn. 
Since then, the extent to which the science in its theoretical 
and practical bearings has developed, and the perfection it has 
reached, are extraordinary. Puck could put a girdle round the 
earth in forty minutes, but we know that a telegraph clerk, or, 
indeed, any one amongst us, could greet the antipodes ere 
Puck had bidden us good-bye. Submarine cables are being 
laid in every sea, and cable stocks are a safe investment. Very 
soon a fourth cable will be laid direct to America, and, perhaj: s 
before next summer, Mother England will give her apron string 
direct to Bermuda, and extend it to New York and Brazil. 
Land lines, with that daring often displayed in spiders’ wets, 
cross each other in all directions, and penetrate across the 
wildest continents. 
Of all men connected with the progress of electrical science 
as a whole, and particularly of submarine telegraphy, we are, as 
is well known, chiefly indebted to Sir William Thomson, not 
only for his brilliant mathematical investigations and deduc- 
tions, but for the utility of his practical inventions in the shape 
of electrometers and other instruments more closely connected 
with the practice of telegraphy. It was his delicate mirror, or 
reflecting galvanometer, which lifted the first Atlantic Cable 
Company out of the mire into which they had fallen for want 
of a more sensitive interpreter of their messages. In this 
instrument there is an arrangement of small magnets with a 
miniature mirror attached, weighing about a third of a grain, 
the whole suspended by a single fibre of unspun silk ; and the 
current coming from the sending station being passed round 
