Notes to Dr. Henderson's Meteorological Observations in 
North-west India and Ydrkand. 
In calculating the elevations above the sea, and the 
dew-point and humidity from these observations, G. H. 
Simmonds's Meteorological Tables have been employed. 
The mercurial barometer has been considered to have 
been without any appreciable error ; and on this supposition 
a comparison of its readings, corrected for temperature, as 
shown by its attached thermometer, to 32° F. with the 
tension, reduced to the latitude of the place of observation, 
corresponding to the boiling point of water, leads to the 
conclusion that the mean error of the hypsometers lies 
between — *! and — '2 of a degree. As thermometers, 
however correctly made, acquire a minus correction after 
some time, and especially after repeated use in boiling 
water, the results of the comparison were satisfactory, and 
show that both the barometer and the hypsometers were 
correct within very moderate limits. This comparison also 
led to the detection of a few evident errors in reading one 
or other of these instruments. These errors have been 
noted in the register, and allowed for in the calculation of 
the height, but the readings remain in their original state. 
A comparison of the readings of the aneroids with those 
of the barometer reduced to 32° F., shows that both the 
large and the small aneroid had large and variable errors 
altogether too uncertain to admit of their indications being 
deserving of much attention, unless they had been very 
recently checked, by being read nearly simultaneously with 
the barometer while the air temperature had not con- 
siderably changed. The aneroids were quite out of 
adjustment, and were certainly not compensated for tempe- 
rature. It is almost inconceivable that they could have 
performed so badly as they appear to have done. It must 
be remarked also that there is a peculiarity in the readings 
showing so frequently a 5 or an 0 in the second decimal 
