42 Mr Galbraith''s Tables jhr Barometric Measurement. 



and laborious, I may say astonishing, exertions that were m^df . 

 And tlie surprise to me, considering the disadvantages under 

 which they laboured, was, not that they accomplished so little, 

 but that they were enabled to overcome so many difficulties, 

 and to do so much. 



Liverpool, \ 

 21s/ March 1828. ) 



Tables for Barometric Measurement. By Mr William Gal- 

 BRAiTH, A. M. (Communicated by the Author.) 



SIR, Edinburgh, Sd April 1828. 



M 



Y attention has lately been directed to draw up and collect 

 a commodious set of tables for the barometric measurement of 

 altitudes, as well as for the ordinary purposes of reducing the 

 usual observations with the barometer. I need not inform 

 you how rudely these are frequently made with the common 

 barometer. This arises both from a bad state of the instruments 

 employed, and the inadequacy of the corrections generally 

 applied to reduce them to a standard point of temperature and 

 level. 



The accompanying tables, from which the necessary correc- 

 tions, in all ordinary cases, may be taken out by inspection, are 

 intended pardy to remedy this inconvenience ; and if you think 

 them worth attention, perhaps you may give them a place in 

 your useful and extensively circulated journal, so that they may 

 be more generally known. I have carefully computed the first 

 table from a formula of our distinguished countryman, Mr 

 Ivory ; and, of course, I have no other merit than the labour 

 of computation. This I have executed for tubes varying in 

 diameter from one-tenth of an inch to seven-tenths, to every 

 hundredth of an inch, thereby including every variety of bore 

 Jikely to be used. The second is merely an abridgment of one 

 given by Schumacher in his Hiilfstafeln. The application of 

 those two will therefore give the absolute height of the mercury 

 in the barometer reduced to the freezing point. 



