482 



EEPORT — 1891. 



Though, as a rule, the temperature of the air was higher than that of 

 the water, there were a good many exceptions to this rule, especially in 

 the months of May, June, July, November, and December. Thus there 

 were five days in May in which the water was warmer than the air, six 

 in June, and four in July, with an aggregate excess in the temperature 

 of the water of 37°. In November and December there were also fifteen 

 days with an aggregate excess of 30° '4, the greatest number being in 

 December, viz., ten days, while on other two days of that month the tem- 

 perature of air and water was equal. The conditions under which this 

 state of things was observed were, as a rule, in summer, when the air 

 temperature was lowered by cloudy and wet, or dull and foggy weather, 

 or by the prevalence of cold winds ; and, in winter, when the conditions 

 were similar, or when frost set in. The most extreme difierence was 

 observed on July 7, when the reading of the air temperature was 53°, 

 and that of the water 65° — a difiFerence of 12°. This was at the close of 

 the period of drought before alluded to. The greatest excess in the 

 temperature of the air above that of the water occurred in March, when 

 on sixteen days it was higher by more than 7°, ranging from 7° to 14°"5 ; 

 and the next in September, in which month there were thirteen days in 

 which the difference exceeded 7°, ranging from 7° to 13°'2. On these 

 occasions the weather was for the most part bright and sunny, or, if 

 cloudy or rainy, very mild, with south or south-west winds. 



The following table shows the mean monthly temperatures of the air 

 and water of the estuary of the Nith at Kingholm Quay, where observa- 

 tions were taken with great i-egularity by Mr. James Lewis, for a period 

 of about nine months, from June 25, 1889, to March 21, 1890. The 

 hours of observation necessarily varied, because the proper temperature 

 of the estuary could be obtained only when the tide was up. For the 

 most part they were taken between the hours of 9 a.m. and 4 p.m., though 

 sometimes a little earlier and sometimes a little later. 



From this table it will be seen that for the period from June 25 to 

 July 31 the mean temperature of the estuary was a fraction of a degree 

 higher than that of the air, and the same thing occurred again in October. 

 In all the other months it was lower, but not to the same extent as in 

 the case of the river temperature. Taking the whole period during 

 which observations have been made, the mean temperature of the air 

 was 47°'7, and of the water 46°, giving a mean difference of only 1°7, 

 instead of 4°-3, as in the case of the river. This result might have been 



