through the mazes of imagination ; while the advancement of 
astronomy, of chemistry, and geology may be appealed to as 
expressive of the advantages of working diligently with a system 
of observation for our guide, and waiting patiently for the de- 
velopment of the truth. 
It has been said, and said too by a great authority, that 
in experimental science we owe much to accident. Depend 
upon it, however, as a general rule, there arc no accidents in 
science. It is true that often in the progress of an investiga- 
tion an unexpected circumstance gives rise to a new train of 
inquiries ; new ideas are the result, and discoveries the con- 
sequence. If that which may be regarded as an accident does 
not generate a clear idea, and generalize a correct system of 
inductive search, it remains a valueless fact. 
Thales, of Miletus, observed, that amber being rubbed at- 
tracted light bodies. Here was a fact, probably of accidental 
discovery, which failed to produce a definite idea ; and remem- 
ber, nearly 2000 years passed away before man detected the 
truth that the electron of the Greek philosopher was a source of 
the all-diffusive agency, electricity. Galvani noted the convul- 
sive movements of frogs, when the moist surface of their bodies 
was in contact with two metals of unequal affinity for oxygen ; 
this generated a correct idea in the mind of Volta. Step by 
step induction has followed in this path, and we have, within a 
period of sixty years, the discovery applied to metallurgical pro- 
cesses of great utility, and to the valuable one of firing simul- 
taneously any number of holes in the operation of blasting 
rocks, by which the sinking of shafts and the driving of levels in 
our mines are carried on with great rapidity and much economy. 
Following on the same tract CErsted proved that a copper wire 
under the influence of an electric current became a temporary 
magnet. It was soon shown that an iron bar placed within an 
helix of such wire acquired most powerful magnetic properties ; 
and within twenty years this knowledge has been applied to 
measure the tread of time, and to be the winged messenger of 
human thought, surpassing beyond all limits the speed of the 
“ tricksy Ariel,” and leaving the hurrying tempest like a laggard 
in its path. These facts were adduced by my colleague, Dr. 
