70 Barometric Measurement of the Height of Cheviot. 



Holy Island, where Sir T. M. Brisbane was residing, and where 

 he had a good set of instruments for the purpose ; while Mr 

 Galbraith, with another set of similar instruments, should make 

 a corresponding series on the top of Cheviot, at times previously 

 agreed upon. 



On the 14th of September 1832, two corresponding series 

 were made, under rather favourable circumstances, between the 

 hours of 11 and 12 noon, of which the following are the means, 

 indicated by general symbols. 



At Holy Island, 59 feet above the mean level of the sea, 



B = 29.849, r = 57.0, i = 57-0 

 on the top of Cheviot, near the eastern extremity, and a few 

 feet under the mark lately erected by Sir T. M. Brisbane, in the 

 place of that formerly occupied by the theodolite, used in the 

 trigonometrical survey *, 



in. / o / o 



5 = 26.993, T = 44.5, / = 44.6 



In like manner, a series was taken in Mr Adie's shop, 58. 

 Prince's Street, Edinburgh, at 207 feet above the mean level of 

 the sea at Leith, by Mr R. Adie, to see what influence horizon- 

 tal distance might have on the results, where 



in. 

 B = 29.591, T = 60.0, t = 60.0 



In which B denotes the height of the mercury in the barometer 

 at the lower station, t the temperature of the mercury in the 

 barometer by the attached thermometer, t that of the air by the 

 detached thermometer, while 6, t, and f, mean the same at the 

 higher stations, though, for the purpose of avoiding all uncer- 

 tainty of the real temperature of the mercury in the barometer 

 tube and cistern, it has been thought desirable, in these obser- 

 vations, to allow both thermometers to come to the same tem- 

 perature, by exposing the instruments to the free action of the 

 atmosphere for an hour before recording the observations from 

 which the deductions are made, since it appears doubtful that 



• It is much to be regretted that substantial permanent marks, which 

 might have been prepared at a trifling additional expense, are not universal. 

 \y left by the Ordnance surveyors at all their stations ; such as a roughly 

 dressed block of stone, with the King's mark, the arrow, upon it, and a cross 

 to point out the exact centre of the theodolite, as it is probable that, in the 

 course qf a very few years, they will be generally irrecoverably lost. 



