p.1

Chicago Nov 12 1870

Dr Sir

Having been appointed Assistant
to the Chief Signal Officer of the Army in
Charge of Telegrams &c, and at his
request I write to ask that you
will carefully reconsider your observations
of the barometer to see whether they are
made & reduced in accordance with instructions;
for upon comparison with those of
the other observers I find reason to
suppose that yours are uniformly too
low.
If you find nothing wrong,
please send me a copy of morning
observations for 10th 11th & 12th, showing
1st the observed height
2 amount of instrumental error if any
3 temperature of the barometer (attached thermometer)
4 amount deducted for temperature
5 amount added for sea = level.