On the Naturalization of Fish; 323 



respiration and food. ' If fish can breathe indifferently salt water 

 or fresh, for one week or one month, and if, in their new ele- 

 ment, translated from salt to fresh, they thrive or grow, fatten 

 and breed, the trial of three weeks or three months is a sufficient 

 proof that they will neither sicken nor die of fresh water. If 

 they can find food, it is indifferent whether the medium is fresh 

 or salt. It is the misfortune of the age to understand every 

 thing without knowing its principles ; just as every man is now 

 a physician. A few, more profound, who chance to know that 

 salmon divide their time between fresh and salt water, possess 

 other reasons, and find other objections ; which they must be 

 permitted to explain for themselves. I ought not, while on this 

 particular subject, to omit one fact, which has come to my 

 knowledge since the former papers were written, on the volun- 

 tary emigration of a fish, supposed to be peculiarly delicate and 

 peculiarly attached to the sea, into fresh water. This is, that, in 

 Virginia, the herring ascends the rivers, even up into the most 

 minute communicating branches, and as far as it can reach ; 

 while a somewhat recent traveller describes them as being sa 

 abundant, that it is impossible to cross the fords on horseback 

 during the season of their migration, without destroying them 

 by the horse's feet. To proceed to the historical condition of 

 this pond. ^ > 



I have already stated the difficulties arising from want of 

 leisure and wealth in the proprietor, added to non-residence I 

 should say, whence chiefly has arisen the difficulty of tracing 

 the results. Let those try for themselves, who consider that all 

 this might have been ascertained in a twelvemonth, and 

 with the same means. Since the communications I formerly 

 made, the Pilchard has been introduced. It swam away briskly, 

 therefore it would not die of the fresh water ; but it has not 

 been retaken. The retaking of individual fish, to ascertain their 

 presence, is a fundamental difficulty, as I before pointed out. 



The Brill has also been introduced since my former list. It 

 has been retaken ; and, within one year, had grown to double 

 the original size. * 



The Turbot. Fifty or sixty were introduced, averaging about 

 eight inches in length. Some were retaken in a year, for the 

 purppse of examination merely, like the former and most others ; 



