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Abstract of Paper on the Change of Temperature ivith Height during Anti-Cyclones 

 on Ben Nevis, and at some Continental Stations. By R. T. Omond.* 



During almost every winter anti-cyclone, with its accompanying cold but calm and fair 

 weather, the temperature at Fort- William is, for part of the time, nearly as low or lower 

 than that on Ben Nevis, 4400 feet above it. The average difference of temperature is 

 16° Fahr. ; Ben Nevis being that much colder, or about 1° for every 270 feet. But in 

 anti-cyclones this normal difference of temperature is widely departed from, the records 

 showing that Ben Nevis has been 17° warmer instead of 16° colder than Fort- William, 

 a departure of 33° from the normal ; and it has frequently been 5° to 10° warmer for a 

 day or two at a time. These data only give the temperatures on the summit of Ben 

 Nevis, and at the sea-level five miles away they give us no information as to what it is 

 in the intermediate air. That there is something unusual in this 4400 feet of atmos- 

 phere is hinted at by two facts, — first, with this abnormal temperature arrangement 

 we always have very dry air on the summit, and very damp air at Fort-William ; 

 second, the difference of the barometer readings at top and bottom is less than the 

 normal difference for the temperature. The former is an inversion of the ordinary 

 humidity conditions — usually the air on the summit is saturated, or nearly so, with 

 moisture, and at Fort- William dry ; the latter, the barometric differences, require a few 

 words of explanation to show what exactly they indicate, and how they bear on the 

 question of temperature. 



Some years ago, Dr Buchan drew up a table giving the observed differences in 

 thousandths of an inch of the barometer on Ben Nevis and that at Fort- William for 

 each tenth of an inch sea-level pressure, and each degree of temperature ; the Ben Nevis 

 barometer being reduced to 32° only, and that at Fort- William to 32° and sea-level, and 

 the temperature being taken as the mean of the Ben Nevis and Fort- William tempera- 

 tures. This table was published in the Transactions Royal Society Edinburgh, vol. 

 xxxiv. p. lx., and a full description of it, and of the method in which it was compiled, 

 will be found in the Introduction to that volume. It is reprinted at the end of the 

 Appendix to this volume. Each column of the table represents, at a certain 

 temperature, the difference of the two barometers for varying sea-level pressures, 

 and the values decrease as we pass down any column to lower pressures, or go from 

 column to column up the temperature scale. 



This table is used to reduce the Ben Nevis barometer to sea-level ; the proper line 

 of the table is indicated by the barometer in Fort- William, and the proper column by 

 the average temperature of Ben Nevis and Fort-William. For example, on the 6th 

 February 1893, at 4 p.m. : — 



* See Journal of Scottish Meteorological Society, vol. xi. p. 65. 



