484 



" head," which had been supplied for the self-recording pressure-tube anemometer, the " head " being placed 

 a few inches above the post and 10 feet above the snow. When the instrument is exposed to the wind, 

 the coloured fluid alcohol in the glass tube oscillates with the fluctuations in the force of the wind, and 

 the usual method of observation is to watch these oscillations for a few seconds and note what appears to 

 the observer to be its average level, the corresponding velocity being then recorded as that of the wind at 

 the time of the observation. 



This method of observing was, however, slightly varied in this instance the observer recorded the 

 extremes of the oscillation instead of the mean. Such an entry as " 16-26 " in the Journal means, therefore, 

 that the force of the wind varied from a minimum of 16 miles to a maximum of 26 miles during the time 

 of observation. It does not follow, however, that the arithmetic mean of two such readings would fairly 

 indicate the average force of the wind, even for the somewhat brief period such an observation might be 

 supposed to represent. At times it would no doubt do so, but an examination of the automatic records of 

 a self -registering pressure-tube anemometer would show that frequently it would not, owing to the fact 

 that relatively strong, but very transient, gusts often occur which are not balanced by corresponding lulls, 

 and therefore have a tendency, supposing such a gust to be included in the observation, to exaggerate the 

 average force obtained. 



It would have added to the value of the observation, therefore, if, in addition to giving the extreme 

 limits of the excursions of the fluid, the observer had also recorded the velocity corresponding to the 

 position upon the scale around which the fluid appeared most frequently to lie. 



A difficulty in connection with the use of the instrument arose from the frequent choking of the 

 "head" and the connecting pipes with drifting snow, necessitating its being frequently dismounted and 

 cleaned. Possibly the small height above the snow at which the " head" was fixed may have been partly 

 responsible for this ; but the trouble would doubtless have been much diminished, and perhaps entirely 

 obviated, if the instrument had been used in the way intended, and, instead of being fixed out of doors, 

 had been taken out only when required for the purpose of an observation. 



The self-recording pressure-tube anemometer was erected on board the ship, the " head " being placed 

 on the mizzen cross-trees, on the southern side of the ship, 34 feet above the sea level, whilst the 

 recording portion of the instrument was put in the signal locker, on the upper deck. The selection of 

 this position for the recording apparatus was unfortunate, and was the proximate cause of the loss of 

 many weeks' records. 



On account of the difficulty which would probably be experienced in keeping water unfrozen in the 

 high latitudes in which the instrument was expected to work, a " non-freezing mixture " had been 

 supplied for use in the anemometer cistern as a substitute for water. The " mixture " consisted simply of 

 water and methylated spirit, to which a small quantity of glycerine was added to give the compound the 

 specific gravity of water. Without much doubt, had the cistern containing this fluid been placed in a less 

 exposed position below deck and the instrument itself presented no difficulty to this being done the 

 fluid would have fulfilled its purpose ; but under the influence of the extreme cold to which it was 

 exposed in the locker it frequently got out of order, and on opening the cistern " ice was found on the 

 top of the liquid, then the spirit, and below that a thick substance like condensed milk." The " mixture " 

 was therefore removed and the cistern "filled with spirit containing only a small amount of glycerine." 

 The result was a decided improvement in the action of the float, although in very low temperatures and 

 calms " the piston was still inclined to work in thick liquid," and " the whole lot had to be stirred up." 

 The extreme cold also affected the ink and the going of the clock; and, as a final result, there were many 

 days on which no record at all was obtained, and many others when the record was of no use. 



The vane for indicating the direction of the wind was placed at another angle of the frame for supporting 

 the thermometer screens, at the height of 12 feet above the snow level. 



OBSERVATIONS. 



The observations relating to wind may be summarized as follows : The direction, as shown by the, 

 vane, was recorded at every second hour, from the time of arrival in Winter Quarters till near the close 

 of the vessel's stay, when the hours of observation were reduced. The force of the wind, as estimated by 



