name as authonty for their own. To be sure, his de- 

 scriptions ^are but little better than none at all, yet allow- 

 ance mustbe made for the difficulties encountered in a 

 fieid of research then quite unexplored. 1 watched the 

 fishes lazily swimming among the sea-bass. Perhaps if 

 Robert Fulton had spent an hour or two in studying the 

 motions of his file-fishes' fins he might have grasped the 

 idea of propelling a boat by a screw under its stern, and 

 saved steam navigation from the long developmental pe- 



(CONCLUDED ON PAGE ,356.) 

 (CONTINUED FKOM PAGE 353). 



riod of side-wheelers. At any rate, he might have 

 found a worse model for a propeller than the file-fish 

 would have been. 



I will try to describe its motions as they appeared 

 to me. As in all the fishes of this order which I 

 have oo^erved, the propelling power is exercised 

 chiefly by the dorsal and anal fins, the tail, that 

 powerful sculling oar so important to other fishes, being 

 degraded to the rank and function of a rudder. Occa- 

 sionally, when disturbed, the fish gave a rapid side 

 sweep of its tail, yet seemed to depend chiefly on the 

 undulating, Archimedean screw motion of the back-fin 

 and its counterpart the anal, though perhaps the caudal 

 would be made use of in a long rapid journey. Like 

 the rest of the family, the fish appears to be sluggish 

 and sun-loving in its habits, passing the day lazily float- 

 ing or flapping its broad sides at the surface. A hori- 

 zontal position was often taken, a sudden and oblique 

 twist of the tail-rudder serving to throw the fish upon 

 its side, in which attitude it would remain slowly pro- 

 pelling itself by a motion of the dorsal and anal, which 

 must be seen to be understood, which I cannot describe, 

 though I have seen it also in the flounder. A slight 

 movement of the pectoral fins, situated as they are be- 

 low and in advance of the centre of gravity, changes 

 the delicate poise of the fish and lowers its head, an 

 oblique motion with the upper edges of the fins turned 

 inward has the contrary effect. Sometimes the fish 

 would assume a strange position, its body upright, head 

 downward, then by a reversed motion of the pectorals 

 it would "back water" until it had raised its tail above 

 the surface as far as the base of its rays ; in this atti- 

 tude it would remain for a short time, wagging its tail 

 with apparent enjoyment. Whether this act indicates 

 pleasure, as in a dog, or anger, as in a cat, I was not 

 able to learn. But the tail seemed such a convenient 

 handle that the temptation to take hold of it was almost 

 irresistible.' When swimming near the surface it 

 would often turn upon its side with a sudden sweep of 



