46 Mr W. Galbraith's Barometric Observations. 



By introducing a more refined calculation with logarithms, 

 the height would have been about 10 or 12 feet more, though 

 it is obtained at considerable risk of error, from errors either in 

 the ordinary tables, or oversights in the steps of the calculation, 

 which to unpractised persons frequently occur; whereas the 

 foregoing requires only a very simple arithmetical computation, 

 where no figure of real utility is suppressed, which is fre- 

 quently done, to make the operation look simpler than it real- 

 ly is. 



Example II. 



On the 12th of September 1829, the following observations 

 were made with Mr Adie's sympiesometer. 



At Edinburgh, 270 feet above the sea. 



S' = 272 fathoms, and t = 57° '7 Fahrenheit ; 

 At the top of Allermuir, on the same day, 



S = 490 fathoms, and t! — 50°-3 Fahrenheit; 

 Hence S — S' = 490 — 272 = 218 fathoms ; 

 And ^ 4- ^ = 57° -7 -h 50° -3 = 108°, which, from the 

 engraved scale on the instrument, gives the factor 

 w = 1053; 

 Whence 218 x 1053 = 229*5 fathoms, or 1377 feet. 



If to this, 270 feet be added, for the height of the lower sta- 

 tion, at Edinburgh, above the sea, we shall have 1647 feet for 

 the height of Allermuir, above mean-tide at Leith. This ex- 

 ceeds the former by about 43 feet, which must be partly 

 ascribed to the unfavourable state of the weather at the time, 

 and partly to a small error in the foregoing formula. On the 

 whole, I consider the mean of these results, or 1625 feet, to be 

 nearly the true height, as I have found it from other observa- 

 tions. 



Example III. 



In the month of August 1830, with a mountain-barometer of 

 tl;xe best construction, the following observations were made at 



