i 1852.1 HEIGHT ABOVE THE SEA. 359 
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! Being now in a part of the country that no European 
ij traveller had ever before visited, I exceedingly regretted 
my want of instruments to determine the latitude, longi- 
tude, and height above the sea. The two last 1 had no 
!' means whatever of ascertaining, having broken my boil- 
I ing-point thermometer, and lost my smaller one, without 
' having been able to replace either. I once thought of 
I sealing up a flask of air, by accurately weighing which 
on my return, the density of air at that particular time 
I would be obtained, and the height at which a barometer 
would have stood might be deduced. But, besides that 
j this would only give a result equal to that of a single 
t barometer observation, there were insuperable difficulties 
in the way of sealing up the bottle, for whether sealing- 
j wax or pitch were used, or even should the bottle be 
I hermetically sealed, heat must be applied, and at the 
I moment of application would, of course, rarefy the air 
I within the bottle, and so produce in such a delicate ope- 
ration very erroneous results. My observations however 
[ on the heights of the falls we passed, would give their 
I sum as about two hundred and fifty feet ; now if we add 
: fifty for the fall of the river between them, we shall ob- 
|| tain three hundred feet, as the probable height of the 
point I reached above the mouth of the river ; and, as I 
i| have every reason to believe that that is not five hundred 
|i feet above the sea, we shall obtain eight hundred feet as 
!| the probable limit of the height of the river at the point 
I reached, above the seadevel. Nothing however can 
accurately determine this fact, but a series of barometer 
or ‘‘ boiling-point ” observations ; and to determine this 
height above the next great fall, and ascertain the true 
