VOL. XXXV.] miLOSOPHICAL TRANSACTIONS. 269 



height of the atmosphere above the level of the sea at given altitudes of mer- 

 cury. But having afterwards, on comparison, found that the observations made 

 in 1703, did not in the main agree with the rules of M. Mariotte, and that 

 the heights of places, as they appeared by those observations, exceeded, gene- 

 rally speaking, the numbers resulting from the tables made by him according to 

 the said rules, he thought it necessary to calculate two new ones, where indeed 

 the results are considerably greater than in the tables framed according to the 

 rules of M. Mariotte; insomuch, that for instance, a place, where the mercury 

 falls to 22 inches, rises above the level of the sea, according to Mariotte, 852 

 toises, or 5112 Paris feet; and, according to Cassini, 1158 toises, or 6948 feet, 

 which makes a diiference of i 836 Paris feet, or 3o6 toises. Dr. Desaguliers, 

 in his dissertation concerning the figure of the earth, (Philos. Trans. N° 386,) 

 has already shown how far the observations made by the gentlemen, who drew 

 the meridian across the kingdom of France, differ from each other, insomuch 

 that there are not 2 in 9 where the number of toises, said to correspond to the 

 heights of the barometer, agree together; and that consequently the heights 

 of mountains, as determined by these observations, are little to be depended on. 



The Doctor's father. Dr. J. J. Scheuchzer, in his journeys over the moun- 

 tains of Swisserland, as they were more particularly calculated for the improve- 

 ment of natural philosophy in its several branches, neglected no opportunity, 

 along with his other observations, to make such experiments with the baro- 

 meter, as might serve to illustrate the qualities of the air, to settle the respective 

 heights of places, and particularly to show how much our mountains rise, as 

 well above the level of the sea, as above other neighbouring mountains, in 

 France, Italy, Spain, &c. Many of these observations are scattered up and 

 down in his writings, particularly his Itinera Alpina, and the several parts of his 

 Natural History of Swisserland, which last work was published in High Ger- 

 man. It would be too tedious to mention all the experiments he made at dif- 

 ferent times, and on different mountains. But the Doctor's design in this 

 paper requires him to be particular in one, which for the height measured both 

 with the line and barometer is, he believes, the most considerable that ever 

 was made, and which enabled him more particularly to examine the two tables 

 made by Cassini the younger, according to the rules of M. Mariotte, and 

 the observations made by hiu) and others, when the meridian line was perfected 

 in 1703. 



This curious experiment was made in the year 1709, at Pfeffers, a celebrated 

 mineral water in the county of Sargans, at the bottom and top of a mountain, 

 which rises from a small brook, called the Taminna, to the height of 714 

 Paris feet, as appeared by letting a line drop down perpendicularly from a tree 



