Loch Lomond during the Autumn of 1885 337 



The position of the index in the thermometers when referred 

 to this scale can be fixed almost to one-tenth of a millimetre, 

 certainly to one-fifth. In thermometer No. 9, I millimetre 

 = 0-285 F. ; in No. 80, 1 millimetre = 0-345 F. ; and in No. 21, 

 i millimetre = 0-31 F. The difference of o-i millimetre 

 between the readings of No. 21 on 5th and on 22nd September 

 cannot be depended on as real. It is probable that between 

 these dates and during the whole of the summer the tem- 

 perature had been quite constant. Between 22nd September 

 and I4th November the whole rise of temperature at the bottom 

 is only 0-25, and it may be confidently affirmed that at a depth 



of ioo fathoms the whole range of temperature during a single 

 season does not exceed 0-3 F. By season is meant the summer 

 ,ind winter half of the year, or the period between the date 

 when heating begins in the spring, and that at which the summer 

 heat has been almost wholly lost, and when the water begins 

 again to assume a sensibly uniform temperature from top to 

 bottom. At 85 fathoms the temperature had begun distinctly 

 to rise on 5th September, and by I4th November it had evidently 

 reached about its maximum. At this depth, therefore, tin* 

 summer range is at least 0-4 F. At 65 fathoms the water had 

 begun to cool between i6th October and I4th November. In 

 order to determine the range at this depth, it will be necessary 

 to have observations r.irlirr than 5th September. 



B. III. 



22 



