THE SHORES OF BRITAIN. 93 
borough for one shilling! The fish are brought to 
the mouth of the Thames in stout cutters, furnished 
with wells, in which they remain alive; hence they 
are sent up in portions to Billingsgate by the night 
tide. The cutters lie at Gravesend: for if they 
were to advance any higher up the river, the ad- 
mixture of fresh water would kill the fish in the 
wells. The liver of the Cod is not the least va- 
luable part of its body, because it melts almost 
entirely away‘into a clear oil, much used in manu- 
factures, 
There is a family of fishes familiar to us, which 
are worthy of a moment’s notice, not only on ac- 
count of their importance as objects of commercial 
speculation, but for their singular and unparalleled 
‘deviation from the ordinary structure. These are 
the Flat-fishes (Pleuronectide), comprising the Tur- 
bot, Plaice, Sole, and some others. Their form is 
very deep, but at the same time very thin, and they 
are not constituted to swim as other fishes do, with 
the back uppermost, but lying upon one side. They 
reside wholly upon the bottom, shuffling along by 
waving their flattened bodies, fringed with the dorsal 
and anal fins; and as théy are somewhat sluggish in 
their movements, they need concealment from ene- 
mies. This is afforded to them by the side which 
is uppermost being of a dusky-brown hue, undis- 
tinguishable from the mud on which they rest; and 
so conscious are they where their safety lies, that 
when alarmed, they do not seek to escape by flight, 
like other fishes, but sink down close to the bottom, 
and lie perfectly motionless. Even the practised 
