110 METEOROLOGICAL OBSERVATIOKS AT LAURIE ISLAND, SOUTH ORKNEYS. 



feet high to the wcvst of Copeland Observatory. Unfortunately it was not possible to obtain 

 a site for this instrument where there was n clear horizon at all hours. In summer, hills 

 to the west cut the solar rays off at about 7 p.m., and in winter the total possible of 

 about five hours was reduced to about half thiit amount by mountains to the N.N.E. 

 The amount of cloud was, however, noted every hour, which helps to sujiplement the 

 somewhat defective sunshine record. The instruments at this station were read and set 

 once a day until 1st November, when the summer party went into residence in the 

 stone hut built during the winter for their accommodation, and after that date hourlv 

 observations were taken until 21st Februaiy 1904, when the station was taken over by 

 the Aro-entine Meteorological Office on the return of the "Scotia." 



The barometer emplo}'ed on and after 1st November was of the Kew Station 

 pattern, Adie No. 564. This instrument was compared at Kew and the Meteorological 

 Office before and after the return of the Expedition, and its correction was found to 

 remain unaltered. Froui a comparison of eighty-nine simultaneous observations made 

 from 24th October to 21st November between the station barometer. No. 564, and the 

 Kew marine barometer, No. A. 520, on board the "Scotia," it was found that the station 

 barometer read O'Oll inch lower than that on the ship after all the instrumental and 

 other corrections had been applied. Too much importance cannot, however, be attached 

 to this difference, owing to the frequency of local squalls in the vicinity of the house, 

 which slightly lowered the barometiic pressure there on many (jccasions. 



The form of publication for the hourly values is that usually employed in the 

 printing of observations from stations of the first order. It was considered after 

 consulting the leading British meteorologists) inexpedient to attempt to compute the 

 relative humidity and vapour pressure of the period 28th April to 4th October from 

 the dry and wet bulb readings, owing to the doubt that attaches to such reductions at 

 temperatures below 10° Fahrenheit. In tlie tables the depression of the wet bulb is 

 given. For the summer months the humidity and vapour pressure were taken from 

 Glaisher's tables. 



With regard to the Richard Hair hygrographs, the traces in winter were so im- 

 perfect, owing to the frec^uency of blizzards, that no systematic use could be made of the 

 charts, which were, however, used in summer as a check on the dry and wet bulb 

 readings when any anomaly presented itself in the readings. 



It is important to observe that, owing to the proximity of cliffs to the west and 

 south-west, the winds recorded at Omond House do not represent the true atmospheric 

 circulation, especially in the case of winds from south, south-west, and west, which were 

 frequently deflected to south-east. With winds from other quarters the errors 

 introduced were small. 



In addition to the ordinary observations, the limit of visibility was observed on a 

 scale of to 12. These values are not printed in extenso, but an abstract of the 

 hourly values will be found in the portion of this memoir devoted to the results of 

 the observations. 



