282 RESULTS OF THE METEOROLOGICAL OBSERVATIONS TAKEN DURING 



It will be observed that on the mean of the whole period the curve is of a very 

 simple character, showing a very slight maximum at 3 p.m., but no decided minimum. 

 The depression of the wet bulb is very small, ranging only from 0°7 to 0°'9. In Autumn 

 and Winter there may be said to be practically no diurnal range in the humidity values 

 deduced by this method ; but in Spring and Summer it will be noticed that the diurnal 

 range is fairly well marked. In the table showing the mean relative humidity for the 

 hours and the day, utilising Glashier's hygrometrical tables for the purpose, it will be 

 seen that in Summer there is a well-marked maximum in the late evening and early 

 morning hours, and a minimum in the afternoon about 3 p.m. The variation between 

 the mean hourly values i.s, however, very small, amounting to less than 3 per cent. The 

 Summer curve of vapour pressure shows the maximum at 1 p.m. and a minimum from 

 about 2 to 4 a.m., but, as in the case of the relative humidity, the daily range is insignificant, 

 the maximum being 0-163 inch at 1 p.m. and the minimum 0-154 inch at 2 and 4 a.m. 

 It is somewhat unfortunate that no use could be made of the curves obtained from the 

 Richard hygrograph during the Autumn and Winter months owing to the frequency of 

 blizzards which interfered with the registration. In connection with the utilisation of the 

 dry and wet bulb thermometer readings for the purpose for which they are intended, it is 

 very desirable that some comprehensive scheme of investigation should be carried out at 

 low temperatures and under different atmospheric conditions with a view towards the 

 preparation of hygrometrical tables to be based upon a definitive formula approved of 

 by the International Meteorological Committee. In this way observations obtained 

 in different countries from the instrument in question could be directly compared with 

 each other, and the results rendered comparable, which is impossible with the present 

 system of each country using tables based on different formuljB. This, of course, 

 applies more particularl)^ to temperatures below the freezing point and to lower 

 temperatures, about which great dubiety exists. 



Mban Humidity, South Orkneys. 



