44 
the water or of substances dissolved in, or diffused through it, similiar to 
our sense of smell. 
With regard to hearing, it is very difficult to arrive at any conclu- 
sion, for what may be attributed in them to the sense of hearing is, in 
most cases, if not all, attributable to vibration. A sudden slam of the 
door, a clap of thunder, or a stamping on the floor will start into violent 
movement a fish lying perfectly still. I remember as a boy, standing by 
a fish pond, belonging to my father, (at which, by the way, before the 
days of aquaria, I picked up a good deal of knowledge on the habits of 
fish,) watching a shoal of roach sunning themselves on the surface. A 
dark cloud was speedily approaching, from which suddenly burst out a 
bright flash of lightning without in the least disconcerting the fish, but 
the instant the thunder sounded, they dissappeared with a dive down- 
wards, scattering in all directions, and I am very much inclined to the 
opinion that it is vibration or percussion alone that supplies to them 
what with us we attribute to hearing. Those who had the pleasure of 
listening to Dr. Powell's recent lecture on " Sound ", will remember that 
his explanation of hearing was, that it is to a great extent, based on sound 
vibrations conveyed through our organs of hearing, to the brain. 
The vision of Fish is peculiarly acute. This is known to all fisher- 
men, who, on a sunshiny day carefully avoid letting their shadow, or 
even the shadow of their rod fall upon the water. I have seen trout 
dart from cover to seize a bait floating midway down the stream and 
before they had reached it suddenly turn back, deterred from their 
object, either by a shadow cast on the water, or by a sight of a man on 
the bank. When a strange fish is put into an aquarium, he at first 
avoids showing himself in the open when an observer is by, but when 
he becomes accustomed to frequent visits he seems to have no objection 
to a stranger and swims about unconcernedly. 
Fish exhibit an inquisitive turn of mind. If a new pebble is 
dropped into an aquarium they watch it from a distance, evidently with 
great curiosity. After a while they will swim around it at a respectable 
distance, till one of them, bolder than the others, makes a dash at it> 
immediately rejoining his fellows. Then one or two will swim round 
and round it, gradually approaching nearer to it, till finally they come 
in contact with it ami, when satisfied that it is an object of no harm, 
