1848.] Elevations of places between Almorah and Gangri. 527 



Explanation of the Elevations of places between Almorah and Gangri^ 

 given in Lieut. Strachey's Map and Journal. 



The elevations of places on my route to the lakes of Gangri, addi- 

 tional to the few that were already determined by the Trigonometric 

 and Barometric operations of Captain Webb, have been deduced, in the 

 way common with ill-equipped private travellers, from the observed 

 temperature of boiling water. 



My thermometer was small and bad, unfurnished with proper boiling 

 apparatus (which is essential to correct observations), and lastly, it was 

 broken before any comparisons could be obtained with a standard 

 instrument to ascertain its error, for which purpose I had sent it to the 

 Simla Observatory. The deduced heights are therefore liable to a wide 

 range of uncertainty, for which I have been obliged to make arbitrary 

 allowances, assisted only by a few boiling observations at or near places 

 of known elevation on my route, which are inserted in the accom- 

 panying table. As my instrument was not readable to less than half 

 degrees, — that is, when boiling in a common kettle over a smoky 

 wood-fire, — the elevations cannot pretend to any precision within 250 

 feet, and I have, in most cases, therefore, made them up to the nearest 

 quarter thousand ; but the other causes of error, affecting measurements 

 of this sort, will at least double that range of uncertainty, and the 

 results cannot be considered anything better than rough approximations 

 within 500 feet or so. 



I have made the calculations by Prinsep's Tables (given in the Asiatic 

 Society's Journal), which, though not strictly correct or complete, suffice 

 for such rough observations. The mean temperature of the stratum of 

 air under measurement (which materially affects the resulting eleva- 

 tion), is calculated as is done by Herbert in his Survey of the Alpine 

 Sutluj (vide Asiatic Researches), by assuming the rate of refrigeration 

 of the atmosphere to be 1° Fahrenheit for every 300 feet of elevation, 

 and by deducing, according to this supposition, the temperature of the 

 air at the level of the sea from the observed temperature and the 

 approximate height. 



I have reduced one or two Barometric observations by Manson, 

 recorded in the Asiatic Society's Journal, for a few places about Ralam 

 and upper Jwar, the mean temperature of the column of air being 

 calculated as just explained, and neglecting the minor corrections, for 

 temperature of instrument and decrease of gravity, as likely to be com- 

 pensated, more or less, by the capillarity of the tube, regarding which 

 no information is forthcoming. 



