344 The adaptation of the Aneroid for surveying in India. [No. 4, 





Aneroid 



Thei 



October 21.— 25.756 



65.0 



a 



21.— 25. 9 



68.0 



it 



21.— 27.175 



72.0 



a 



22.-27. 75 



73,5 



tt 



22.-27. 88 



75.5 



tt 



22.-26.725 



81.0 



>t 



22.-27. 87 



80.0 



it 



23.-27. 77 



81.5 



tt 



23.-27. S7 



78.5 



9f A. m. Monastery, Mahabaleshwar. 



4 p. m. Top of Tai Ghaut. 



5 p. m. Bottom of do. 

 Top of Ghaut. 

 Bottom of do. 



Top of Ghaut near Poona, 6 p. m. 

 Poona lines. 10 p. m. 

 Do. do. A\ p. m. 

 Do. do. 10 a. m. 



" A very slight examination of these observations will show how sen- 

 sibly the Aneroid is acted on by the smallest undulations of the ground, 

 and that it acts as freely at 25 inches as at 30. 



" They make no pretence to great accuracy, because most of them 

 were taken when the palkee in which I was carried was in actual 

 motion, but this only proves more strongly the value of the instrument 

 for general purposes. 



" When the merits of the Aneroid become known, and confidence is 

 placed in its indications, it will probably supersede all other portable 

 instruments for ascertaining the heights of mountains : I have there- 

 fore prepared the following table, which will enable any one who can 

 multiply and divide, to obtain altitudes with all the accuracy that is 

 required for practical purposes. The formula used in the calculation 

 is given by Poisson in the second volume of his Traite de Mechanique ; 



(2(«-Hl)\ h 



1 -f J Log.— 

 1000 / hi 



" Where t and t are the temperatures of the air in degrees of the 

 centigrade thermometer at the two places of observation, h and h the 

 length of the barometric columns, and Z the height in Metres. 

 "Table to facilitate calculations of heights of mountains. 



32° 



52416 



47° 



54163 



62° 



55911 



77° 



57658 



33 



52532 



48 



54280 



63 



56027 



78 



57774 



34 



52649 



49 



54396 



64 



56143 



79 



57890 



35 



52765 



50 



54512 



65 



56260 



80 



58007 



36 



52882 



51 



54629 



66 



56376 



81 



5S124 



37 



52998 



52 



54745 



67 



56493 



82 



58240 



38 



53115 



53 



54862 



68 



56609 



83 



58356 



