On the method of measuring Heights hy Boiling Water. 183 



the great differences in different barometrical measurements 

 oftlie same elevations, and the differences observed betwixt 

 different thermometers exposed to the air in the same place, 

 which I have observed on comparing three together to 

 amount often to 1 4°, and never to less than |°. 



I took the following method to obtain an exponent of the 

 value in feet of each degree of the diminished temperature of 

 boiling water. 



The elevation of Quito is, according to Boussmgault, 

 9524; and water boils at 196^-25; 212°-196"-25 = 15°-5. 

 9524-^ 15-75 = 604 ft. 6 in. nearly. Neglecting the fraction as 

 unimportant, I assumed 604 feet for the value of the degree, 

 and began my observation on the conical hill of Javirac, 

 which backs the city, and is calculated at 729 feet in height. 

 Water boiled here by two thermometers at 195°. Then 

 196°'25 -H 195 = r25, difference of boiling water between 

 the hill and the city; and 1-25 x 604 = 755 feet; difference 

 26 feet. I next ascended the volcano of Pichincha, and found 

 at the foot of the crater B. W. 1 86°. 2 1 2° - 1 86° = 26° X 604 

 = 15' 730 feet; and adding 246 feet, the difference between 

 this point and the summit, reckoned at ]5'-976. There could 

 be httle error in the calculation. I next applied this formula 

 to the heights of several places calculated by Humboldt, and 

 where the heat of boiling water had been ascertained by 

 Caldas. 



Thus Bogota, height according to Humboldt 8694 ft. 

 B. W. according to Caldas 197°-6 8712 



Difference 18 



Popayan, according to Humboldt 5823 



B. W. 202°-21 5922 



Difference 99 



Pasto, according to Humboldt 8572 



B. W. 197°-6 8712 



140 ft. 

 The differences here are in four points 27 feet, 18, 99, 

 140. With respect to the hill of Javirac, commonly called 

 El Vanecillo, I suppose the measurement to have been made 

 by the Academicians. But iheir calculations generally differ 

 from those of Humboldt, as in the case of Quito; the former 

 giving 9371 feet, the latter 9537; Pichincha 15,606 feet, 

 Huniboldt 15,976; Chimborazo 20,583, Humboldt 2 1,414. 

 But even a difference of sites is sufficient to account for the 

 27 feet on ground so unequal as that of Quito. The 18 feet 



