422 



APPENDIX. 



Temperature of Lalce Superior. 



It will be observed that the fluctuations of temperature noticed 

 at lower points on the lake chain, about the latitude of Michili- 

 raackinac, have also characterized the entire length of Lake Supe- 

 rior. The atmosphere observed at three separate times, during 

 twenty-four days, by Fahrenheit's thermometer, during the 

 months of June and July, has varied from an average tempera- 

 ture of 62° to 88°, agreeable to masses of clouds interposed to 

 the rays of the sun, and to shifting currents of wind, which have 

 often suddenly intervened. Its waters, spreading for a length of 

 five hundred miles from E. to AV., observed during the same time 

 by as many immersions of the instrument, has not varied more 

 than two degrees below or above the average temperature of 55° 

 m mere surface observations. 



