SCOTT. — METEOROLOGICAL INSTRUCTIONS. 15 



hourly observations, two-hourly, or in default of these four-hourly 

 readings may be registered. They should always be at equidistant 

 intervals of time. 



The logs supplied are ruled for two-hourly observations. 



Barometers. — ^The barometers supplied are of two kinds, marine 

 barometers and aneroids. The latter are supplied for use on 

 sledge expeditions and for determination of heights. 



The mercurial barometers are the only barometers to be used 

 for the regular observations. They should be suspended in 

 some place where they will be shielded from sudden changes of 

 temperature. 



The aneroids must be carefully protected from blows or falls, 

 which might seriously affect their action. Whenever opportunity 

 offers, especially before and after theu^ employment on any ser- 

 vice, e. g.y an exploring expedition, the aneroids used should 

 be most carefully compared with the mercurial barometers, giving 

 the temperatures at each comparison, and the results of such com- 

 parisons most carefully noted in the log. 



It may, perhaps, not be out of place to remark that the omission 

 to make such entries in the logs of comparison of barometers, &c., 

 and of the distinguishing marks and numbers on the instruments 

 actually used, &c., will most seriously depreciate the scientific value 

 of the registers though otherwise most carefully kept. 



Temperature. — The thermometers should be suspended in some 

 position where they will show the true temperature of the open 

 air, and will be affected as little as possible by the warmth of the 

 ship. For this reason, while the Expedition is in winter 

 quarters, they should if possible be placed in an observatory at 

 some distance from the ship. 



Two thermometer screens are supplied for these observations, 

 besides the ordinary small screens for use on board ship. They 

 should be erected on posts, so that the bottom of the screen should 

 be at a level of 4 feet above the surface of the snow ; but, of 

 course, experience will alone show whether a height of 4 feet above 

 the snow is sufficient. 



The screens are furnished with doors at the back as well as in 

 front, so as to allow of the reception of several thermometers, 

 which may thus be placed back to back. 



If any rime is deposited on the instruments it should be care- 

 fully removed some time (if feasible about half an hour), before the 

 observation. 



The maximum and minimum thermometers should be placed in 

 the screen and read regularly at the latest observing hour in the 

 evening, if not at midnight. 



In addition other thermometers, both ordinary and registering, 

 are supplied for various experiments. 



As regards the pocket thermometers, it will be found a very 

 good plan, in order to ascertain speedily the true temperature of 

 the air, to pass a strong string through the hole at the top of the 

 mounting and swing the thermometer round the head for about 

 half a minute. 



