ATKINS— THE SALMON AND ITS ARTIFICIAL CULTURE. 245 



from June 17 to July 15, 1872, do not show any marked increase in 

 temperature during that time.* 



The number of salmon bought in June, from the 1st to the 15t-h, was 

 231, and the average weiglit 12.2 pounds ; from June 10, to 30, 309 

 salmon, averaging 12.5 pounds; from the 1st to the 8th of July, 152 

 salmon, averaging 12.2 pounds; which shows a remarkable uniformity 

 in weight at different dates. Of the whole number bought, 692, there 

 were only three that weighed less than eight pounds ; one of these 

 weighed seven, another six, and another two pounds. The largest 

 weighed twenty-eight pounds.t 



It was impracticable to distinguish between the sexes, and I bought 

 indiscriminately. Toward the close of the season, however, distinctive 

 marks were quite perceptible.t 



The dark color of the water and of the bottom in the salmon pond 

 tended to a high summer temperature. From June 20 to the close of Au- 

 gust four observations daily were made on the temperature of the water, 

 both at the bottom and at the surface, and of the air ; the hours being 

 sunrise, 7 a. ra., 1 p. m., and 9 p. m. The bottom temperature was ob. 

 served at the depth of 10 feet in June, and 8 feet in August, by means 

 of a milk-can sunk to the bottom and kept there all the time except 

 when making the* observation ; it was then drawn up by a line that 

 was constantly attached to it ; the cover was removed, and the bulb 

 of the theomometer being plunged into the water the mercury quickly 

 settled at the proper point. I think this a very safe and accurate 

 mode of observation, as it is cerfeiinly a very simple one. The 

 mean temperature at the bottom on Juae 20 was 00° F. and at sur- 

 face 71O.0, the mean temperature of the air being 64°. The highest 

 bottom temperature observed was 62°, and the lowest 60°. The mean 

 for the last eleven days of June was, air, 64°.38 ; bottom, 00°.53 ; surface, 

 72°.62 ; the water at the surface -baiiig thus about eight degrees 

 warmer, and at the bottom about four degrees colder, than the air. In 



* The mean of six observations of surface temperature in the chaunel between 

 Bucksport and Verona on June 17 and 18 is 61°. 8 F. ; at bottom at same place in 30 feet 

 of water the mean of five observations on same days is 46°.4 F. On 7th, 8th, and 9th 

 July six observations at same point give a mean of 66°. 3 F. at the surface, and 50°. 3 

 F. at the bottom. Observations made at the south end of Verona fail to show any 

 higher temperature between July 10 and 15 than between June 19 and 23. Obser- 

 vations in the main channel of the Penobscot opposite Bucksport might give a dif- 

 ferent result, but not, it is believed, to a great degree. (See table 4.) 



tThe weight was arrived at by estimate, at sight, no practicable mode of weighing 

 the fish presenting itself. Persons accustomed to handling and weighing salmon soon 

 learn to judge their weight by the eye so accurately that an error of a pound in the 

 weight of a fish of average size will seldom occur. But there is, of course, a greater 

 liability of error than there would be with the use of instruments, and this fact must 

 be borne in mind in considering the statements of weight of salmon bought. (See 

 table 8.) 



t As the proportion of the sexes was, however, quite satisfactory, as was found in the 

 fall, the females caught from our pond outnumbering the males nearly two to one. 



