VOL. XXXV.] PHILOSOPHICAL TRANSACTIONS. 285 



The heights of these mountains, in general, seem rather too great. This 

 indeed is easily accounted for, as they were measured by trigonometrical obser- 

 vations, which will, as noticed before, because of the refraction of the air, 

 give the heights greater than they really are. But what confirms it still more, 

 is, that according to the tables above, the numbers which answer to the heights 

 of the Mercury, as they were observed at the top of some of those mountains, 

 are considerably less, and that even Mons. Cassini's own numbers, which yet 

 we have by some undoubted experiments shown to be too great, fall often 

 short. It will be enough to mention two or three instances. At the Tower of 

 Massane in Roussillon, the Mercury stood at 15^ inches, and the height of 



that place was determined trigonometrically, to be 397 toises. 



Now 25-iV inches answer, according to Mariotte, to ... . 342 



According to Cassini 392a 



According to Dr. Scheuchzer 330 



At the top of the mountain called la Coste in Auvergne, the Mercury stood, 

 Oct. 9, 1700, at 23-1- inches, and the height of this mountain was determined 



trigonometrically to be 851 toises. 



Now 234- answer, according to Mariotte, to 644-i- differ. 206^ 



Cassini 826^ 24-|- 



Dr. Sheuchzer 66li 189^ 



The difference is still more considerable with regard to the high mountain 

 Mont d'or en Auvergne, the height of which was determined trigonometrically 



to be 1040 toises. 



At the top of this mountain, the Mercury fell, according to an observa- 

 tion made by F. Sebastien Truchet, June 8, 1705, to 22-|-l inches, which 

 answer, according to 



Mariotte, to 707i toises, differ. 332-f 



Cassini, to ; 925^ 1 14^^ 



Dr. Scheuchzer 7'27i 312J- 



As to the mountains of Switzerland : the barometrical observations made by 

 the Dr.'s father on several of the highest, show, that they rise aloft, above all 

 the neighbouring ones in France, Spain, Italy and Germany. And that it 

 must be so appears further, because from their elevated tops, they dispense 

 their waters to all the European kingdoms and provinces around them. Its 

 valleys and lower parts too, as they are considerably remote from the sea, rise 

 also in proportion above the level of it. It is true, the ascent thither is but 

 gradual, in proportion to the remoteness. At Zuric, for instance, which lies 

 towards the northern borders of Switzerland, the mean height of the barometer 

 has been observed at 26-5*3- inches, which give the elevation of that town, above 



