THE REDUCTION OF THE BEN NEVIS BAROMETER TO SEA-LEVEL. 547 



by low temperatures ; and as a rule high temperatures were associated with high sea- 

 level pressures. The table therefore only extends as low as 27*400 inches up to a mean 

 temperature of 28°; it stops at 27'600 for the next two degrees, at 28'000 from 31° to 

 45°, at 28*500 from 46° to 60°, and at 29"000 from 61° to 75°. This table has been 

 used to reduce the readings of the Ben Nevis barometer at every hour of each day for 

 a period of over ten years, and the limits of the table have included all cases except a 

 few at very high pressures, — 31' inches and upwards, — and some at temperatures below 

 16°. For these it was easy to extend the table by extrapolation, and the general law 

 that a wide range of pressure is only needed at low temperatures, and that high 

 temperatures are associated with high pressures, has been found to hold good 

 throughout. 



An investigation into the accuracy of this table is in progress, the results of which 

 will appear in a subsequent volume ; for general use as applied to mean values, any 

 changes or modifications will be very slight. Corrections, however, will need to be 

 applied to the values in the table in connection with the season of the year and the hour 

 of the day at which observations are made. 



