155 



From eight in the evening of the 30th of September, to 

 half after ten in the morning, of the first of October, the ba- 

 rometer had varied only 0*2 of a line. According to the barome- 

 tric method of Deluc *, we find the following heights, adding 

 11 toises for the elevation of Mr. Pasley's house above the 

 level of the sea : Pino del Dornajito, 516 toises j Station of 

 the Rocks, 1518 toises j Cavern of Ice, 1757 toises ; foot of 

 the Piton, 1847 toises ; Summit of the Peak, 1929 toises." 



I have recalculated Mr. de Borda's observations, con- 

 jointly with Mr. Matthieu, after the method of Mr. Laplace j 

 and, supposing the temperature of mercury equal to that of 

 the air, and reducing the station to the level of the sea, we 

 obtained for the Pino del Dornajito 533 toises ; for the 

 Estancia de los Ingleses, 1 555 toises ; for the Cavern of 

 Ice, 1799 toises ; for the Foot of the Piton, 1892 toises 5 

 for the Top of the Volcano, 1976 toises. This last result 

 differs from that of the trigonometrical measurement twice 

 as much as the height obtained by the formula of Deluc. 

 We shall discuss farther on the causes of error that may 

 have affected the particular operations. 



It commonly happens, when the application of small cor- 

 rections to barometrical and thermometrical heights is in 

 question, that travellers, who have made observations to- 

 gether, do not fix on the same numbers, as means of good 

 observations. 



Messrs. Varela and Arguedas give, in their memoir on the 

 measurement of the Peak, the following barometrical heights : 



inch. lin. 



1 . Pino del Donajito - 25 0*86 Th. 17° R. 



Level of the Sea - 28 4 00 191 



6 



* Compare Fleurieu in Marchand's Voyage, t. ii, p. 11. 

 Forster (Observat. during a Voy. round the World, vol. 1, 

 p. 22) allows the Peak 12340 english feet, or 1931 toises, 

 from Borda's barometrical measurement. 



2 G 



