p.1

Copy

Chicago Nov 18. 1870

Dear Sir

I have your prompt answer to
my letter & will tell you what is
the matter:

Table VII p. 257 (Loomis) gives the
correction for 0.10 inch in the barometer
and must be multiplied by ten, by
removing the decimal point one figure
to the right before it is used as a divisor
for your elevation.

On Nov. 13 you should have divided by
914. (instead of 91.4) See Loomis p. 286
where the table figures are changed as
above. You will notice that your
correction for 582 feet is less than is
there given for 70 feet!

Yours truly
IA Lapham
assistant

Sargent F. H. Fletcher