270 



PHII-OSOl'HICAL TRAKSACTI 



[anno 1728, 



at top full to the bottom. At the bottom of this mountain, near the Taminna, 

 the mercury was by repeated experiments observed at 25" Q^'", and at the top it 

 descended to 24" 1 14-'", so that it fell just 10 lines for 714 feet, which gives 

 about 7 1 Paris feet for a line, if the heights answering to every line were sup- 

 posed to be equal. 



Dr. S, here remarks, that in this paper he uses Paris measure, viz. of toises 

 C) feet (') inches (") and lines ('")• Every toise being 6 feet, the foot is 

 divided into 12 inches, and the inch into 12 lines. 



The heights of the barometer at the bottom and top of the mountain being 

 thus given, the height of it should be, according to M. Mariotte, II 6° o' 8" 

 W'", or 696 Paris feet 8" 1 1'", which falls 17' 3" l'" short of the true height; 

 and according to Cassini 153° 3' 8", that is, 921 Paris feet 8", which exceeds 

 the true height by 207 Paris feet 8 inches. By which it appears, that the table 

 made according to the rules of Mariotte is much preferable to that of Cassini 

 the younger. The same was likewise confirmed by another experiment made 

 in June 1715, on the steeple of the cathedral at Zurich. At the foot of the 

 steeple the barometer stood at 16" lO'", and at the top at 26" 7-l'", and the 

 height of the steeple was found by the line, 241 Paris feet 4 inches, which 

 gives very near 6q Paris feet for one line. According to the table of Mariotte, 

 the height of the steeple should have been 237 Paris feet; according to Cas- 

 sini, 265; and according to the new calculation following, made pursuant to 

 the experiments above, it comes to 243° 16" 2'", or about 2 feet more than the 

 true height. 



It appearing by the experiments made at Pfeffers, that from 25" Q-i-'" the baro- 

 meter descends to 24" W^'", that is, just 10 lines for the height of 714 feet; 

 and the expansions of the air being reciprocally as the heights of mercury, his 

 uncle, Dr. John Scheuchzer, undertook, pursuant to these principles, and the 

 properties of the hyperbola, to calculate a new table, after the following 

 method. 



So is the difference of 

 the logarithms of the 

 height of Mercury near 

 the sea, 28" l'", to any 

 lesser height, as for in- 

 stance 28" O'", that is 

 337 — 330, or 

 1011 — 1008 

 12906 



As the difference of 

 the logarithms of the 

 two given heights 

 of the barometer 

 25" 9i'" and 24" 

 1 14.'", that is 309+ 

 and 299i, or 

 928 — 898 

 142717 



Is to 1 foot. 



To the height of 

 the atmosphere 

 above the level 

 of the sea, as it 

 answers to one 

 line of Mercury 

 is 



64' 6" q'". 



Thus the height of the atmosphere at 28" appears to be 10° 4' 6' 9'"; but. 



