1851.] The adaptation of the Aneroid for surveying in India. 345 



39 53231 54 54979 69 56726 84 584/2 



40 53348 55 55095 70 56842 85 58589 



41 53464 56 55211 71 56959 86 58706 



42 53581 57 55328 72 57075 87 58823 



43 53697 58 55444 73 57192 88 58939 



44 53814 59 55561 74 57308 89 59055 



45 53930 60 55677 75 57424 90 59172 



46 54046 61 55794 76 57541 91 59288 



" Rule. — Multiply the number in the table opposite to the mean of 

 the temperatures of the two places in degrees of Fahrenheit, by the 

 difference of the barometric heights, and divide by their sum. The 

 quotient is the height in feet. 



"Example. — On the 20th October, 1850, the barometer stood at 

 29.85 in the Mhar river near the sea, the thermometer indicating 83.5 ; 

 and at the Monastery Mahabaleshwar it fell to 25.79, and the thermo- 

 meter to 68.5. Required the height. Here the mean temperature is 

 76°, opposite to which in the table is found 57541, which being 

 multiplied by 4.06, the difference, and divided by 55.64, the sum of 

 the barometric heights, gives 4198 feet, the height required. 

 " Table of Heights found by the Aneroid. 



Kenesore above the level of the sea, feet 665 



Monastery Mahabaleshwar, feet 4 1 98 



Mount Charlotte above the Monastery, feet 324 



Mount Charlotte above the level of the sea, feet 4527 



Tai Ghaut, feet 1362 



Height of Ghaut above Poona, feet 1216 



Poona above the level of the sea, feet 2025 



"These heights, as far as I have been able to ascertain, coincide very 

 nearly with the heights ascertained by other means. Indeed no single 

 observation of the barometer at one of the places could be expected to 

 give it more accurately. 



" Leslie's rule is very convenient, and sufficiently accurate ; but the 

 correction for the temperature of the air at the two places is often 

 neglected in practice, — and even in some scientific works the fact of a 

 correction being required is not mentioned. But this correction can- 

 not be omitted, because in the case of Mahabaleshwar it amounts to 

 upwards of 400 feet, and in the case of Poona to about 180 feet. The 



