DO Observations on the Natural History 
be compared to the four oars of a boat, floating freely in the 
water, but attached by leathern loops to the sides : if in this 
state the boat be urged forward by the winds, the oars are soon 
forced back by the water and laid alongside the vessel. From 
not making use of their limbs in thus gliding through the water, 
it sometimes happens, that these animals, in the act of changing 
their direction, roll over, and afterwards right themselves, as 
soon as they have got on their new course. The same thing 
occurs to lampreys, which, in gliding along, sometimes roll over : 
and when they descend to the bottom, if they wish to remain at 
rest, and preserve a rectilinear position, they are constrained to 
attach themselves to some solid substance, by making use of their 
mouth, which adheres on the principle of suction, else, having 
neither feet nor fins to maintain themselves straight, they are 
obliged to lie down on their sides. These facts seem to shew 
that the principal use of the fins in fishes is to maintain the 
body in equilibria, as the learned M. Cuvier has observed. 
With respect to the movements of the adult salamander in 
water, as compared with those of the proteus, the authors ob- 
serve that he is less agile. This may arise from various causes, 
but principally from the form of the tail, which is not only of 
less size, but is less adapted for swimming. The larvae also of 
the salamander are less agile than the proteus, but in that state 
they swim with more facility than afterwards. This probably 
arises from the tail in the larva state being proportionally larger, 
and also from the larva possessing a lower specific gravity than 
the adult animal, except when the latter has recently emerged 
from his winter torpor. That the larvae have a lower specific 
gravity than the adult salamanders, is inferred from the fact 
that they are able to sustain themselves in water, at whatever 
height they please, only by moving, from time to time, in a slight 
degree, their claws and tail. It is beautiful to see them continue 
thus suspended, and as if balanced, on their four limbs in the 
water, like a bird librating in the air : and afterwards, by strik- 
ing the water behind them, and by a slight movement of the 
tail, transfer themselves from one place to another. 
The authors subjoin a few remarks on the movements of these 
several animals on land. Salamanders move from place to place 
only by a simple motion of the limbs. They have neither the 
