ATMOSPHERE OF GREAT BRITAIN AND ON THE CONTINENT. 41 



Dust and Temperature. 



In Part I. diagrams are given showing the maximum and minimum temperatures and 

 the amount of dust in the air at the dates of three sets of observations. An examination 

 of these diagrams seemed to show that the dust has an influence on the maximum and 

 minimum temperatures, as the highest maximum temperatures were observed on the days 

 when the amount of dust was greatest. The dust also seemed to have an influence in 

 checking the fall of the temperature at night, i.e., high dust was generally accompanied by 

 high mean temperature. We, therefore, naturally turn to the observations of 1890 to 

 see if they also support this conclusion. The observations made on the Continent being 

 too fragmentary, it is unnecessary to consider them. Passing over these, and coming to 

 the set of observations corresponding to those shown in the diagrams given in Part I., we 

 come first to the Kingairloch observations. As already stated, the weather during the 

 period of these observations was much disturbed by frequent cyclones. The skies were 

 generally cloudy, and consequently solar and terrestrial radiation would have but little 

 influence on the temperature of the air. The Kingairloch observations of 1890 are 

 therefore of little use for our purpose, as the maximum and minimum temperatures would 

 be determined principally by the winds. It may, however, be stated that during the 

 period of the observations the mean temperature of all the weeks was below the average, 

 sometimes as much as 5° and 6°, and that during the whole of this period the amount of 

 dust was much lower than in 1889, and was probably much below the mean, as excep- 

 tionally low readings were frequently obtained during this period. 



On examining the Alford observations the result is similar to that pointed out in the 

 diagram for 1889. Mr Buchan having again kindly supplied me with a copy of the 

 Logie Coldstone temperature observations for 1890. (It may be mentioned that Logie 

 Coldstone is one of the Scottish Meteorological Stations, and is situated in a south- 

 westerly direction at a distance of about 10 miles from Alford.) From these observations 

 I find that the highest maxima were recorded on the 8th, 1 3th, and 1 4th ; on these 

 days the temperature went up to 72° or more. From the table for 1890 it will be 

 seen that on these days the dust was also about its maximum. Again, the lowest 

 minimum was recorded on the 10th, at which date the dust was also at a minimum. It 

 would, however, be rash to draw a conclusion on so important a point from so few observa- 

 tions as are yet at our disposal. As has been already stated, we must have more observa- 

 tions, and the observations of radiation, both solar and terrestrial, must be continuous 

 before we can get any satisfactory answer to this question. 



As an illustration of the influences at work affecting the temperature of the air, I find 

 that if we add to the diagram showing the dust, and the temperature, another curve to show 

 the number of hours of sunshine, we shall find this latter curve and the curve of maximum 

 temperature to be very similar, and therefore, the high maxima may be due to long 

 hours of sunshine. Since the curve of maximum temperatures follows the curve of hours 

 of sunshine, the dust curve must also follow the curve of sunshine, all three rising and 



VOL. XXXVII. PART I. (NO. 3). H 



