54 STRENGTH OF FISHES. 



Accordingly, when Professor Borelli of Naples, by way 

 of experiment cut off with a pair of scissors, both the 

 breast and vent fins of fishes, he found that all their 

 motions afterwards were unsteady, and that they 

 reeled from right to left, and up and down, in a very 

 irregular manner. 



Fish raise themselves in the water by expanding 

 their swim bladder, and consequently lessening their 

 weight l , as is shown in the figure, where the squares 

 a, by c, represent the relative expansion of the swim 

 bladders, d, e y f. Atf, represented by the square c, the 

 swim bladder is greatly compressed, and the fish is 



(1) Technically, Specific gravity . 



