1 1 6 Chemical and Physical Notes 



The aneroid barometer has been mentioned as having, in 

 some respects, the same advantages as the hypsometer, and 

 it might be thought that the aneroid can, on such excursions, 

 replace both the mercurial barometer and the hypsometer. 

 But this is not so. The aneroid is a spring-balance, and its 

 spring soon gets tired, so that, for instance, on an excursion 

 in mountainous countries, it might, on arriving in the evening 

 at the camping place, show a certain pressure of the atmo- 

 sphere, and the next morning it might show a different 

 pressure, even although the real pressure had not varied in 

 the interval. If the temperature of boiling water varies in 

 the same place, it is proof that the pressure of the atmosphere 

 has varied. But although the aneroid cannot replace the 

 hypsometer, it may with advantage be used in connection 

 with it for determining local variations of height or of atmo- 

 spheric pressure during one day. The night and morning 

 comparisons with the hypsometer give its error and rate for 

 that day. 



Examples of Rapid Variations of Atmospheric Temperature, 

 especially during Fohn. 



The following pages contain the record of peripatetic 

 meteorological observations made at different times. They 

 are reprinted from a paper 1 on this subject published in the 

 Proceedings of the Royal Society in 1894. 



" The variation of the temperature of the air in the course of a day is 

 a matter of familiar observation. It depends in the first instance on the 

 relative positions of the locality and the sun. The temperature is generally 

 highest a short time after the sun has attained its greatest altitude above 

 the horizon, and it is lowest some time after it has attained its greatest 

 depression below the horizon. Observations made at regular intervals 

 over the twenty-four hours show a more or less regular rise of tempera- 

 ture during the early part of the day and a similar fall of temperature 

 during the latter part of the day and the evening. When the interval 

 between the observations is diminished the regularity of the march of 

 temperature is found to diminish also, but the great variability of the 



1 ' On Rapid Variations of Atmospheric Temperature, especially during Fohn, 

 and the methods of observing them,' by J. Y. Buchanan, F.R.S. Proc. R. S. 

 (1894), vol. Ivi. p. 1 08. 



