124 Mr GaihraLitli^s Barometric Measurement of 



incorrect, and consequently the former has been preferred in our 

 calculations. < 



After comparing our barometers at the Observatory, Mr J. 

 Adie and I set out, on the 25th of August 1828, on a short 

 tour, by way of Stirling, Callander, the Trosachs, and Loch 

 Cathrine, so as to combine a little amusement with our more im- 

 portant pursuits, and without interfering with their necessary 

 accuracy. Indeed, if a few of the more generally useful instru- 

 ments of thai; kind were always carried by our scientific travel- 

 lers, the axjcumulation of important facts, and valuable materials, 

 conducive to the progress of general knowledge, would be great- 

 ly increased. 



The barometers were marked. A, B, C, and D, and, taking 

 A as a standard, the mean index errors were as follows : 



A 



Inches. 



B 



Inches. 



c 



Inches. 



D 



Inches. 



0.000 —0.033 -1-0.021 —0.015 



On the 27th of August 1828, at about 11 o'clock forenoon, 

 with barometer A, I arrived at the Cairn, on the top of Ben- 

 Lomond, in which is placed the pole erected by the Ordnance 

 surveyors, which marked one of their stations. 



I. — Observations made with Barometer A, on the Top of Ben-Lomondy 

 the Cistern being 2 feet under the extreme summit. 



On account of the gradual rise in the height of the barome- 

 ter, from eleven to twelve o'clock, as well as from occasional in- 

 terruptions from a company of ladies and gentlemen, who arri- 



