354 COMPUTATION OF ALTITUDES. 
TABLE B. 
Corrections for horary oscillations. 
ЖЕ. Geis. е EVE ES BUS --.005 | 1р. 0....... e III + .007 
Бү re Ee LOAMT РЕ АРТЫН ААА ANDA + .020 
Tw CIT eee ee a eee A st Вр. Wes oss once swans жаз», eevee + .029 
Ti eae 220222222: COM aS лз з ИТТЕ С + .033 
ғазы a а cae on 352 Тш. PRR Pr Rer + .030 
ыы 2. IL. RESI PS Fees cose see eves нане + .022 
ls in ce cho угуз ge ee eee ree + .018 
мм еле ck ee ee nece ere + .010 
ERA S MA E J--004 | 9р. m... e: Sess а ue сс, + .008 
In calculating the corrections for the observations made by Sergeant Lint, on a trip from 
Fort Benton through Lewis and Clark's Pass, between the Tth and 17th of September, 1854, 
there being no simultaneous observations made at Fort Benton, the following table of hourly 
corrections was deduced from a series of simultaneous observations at Cantonment Stevens, 
made at the hours of 1 a. m., 9 a. m., 2 p. m., and 7 p. m., from which the hourly corrections 
for these hours were determined, and the intermediate ones interpolated. 
TARDE... 
Corrections for horary oscillations. 
Hünrisl КЕЗГІ e e es YE 5415 Сри н Sd d 29 е VE ‚ -{.025 
TW ы ае чике ме тк ы 555245 — 035 3 p. ТИ; 423 53 Sey wees d: Vd rv қ. .040 
BN Mics cers cece secs eves sees —.021 4 p.m.«eseeee hn es .048 
B WR Redcar SL ee te wine ЕЧ DEE 5ор.ш..............»......... . .03T 
NS Sere eee ERR REY. ur ITA —.008 6 р.ш...........++ 53646. ‚082 
Lb Gi tid epo Here бл. буйт —.003 SQunseb.sen kno CIENTS wet .030 
ЖЕЗ ыы Сере viret: e 40091 Ep ini ол». ‚024 
lp. m. ҚЫ уы IS REN Г .012 8 р. Meneses cee III .016 
ABNORMAL OSCILLATIONS. Е 
In preparing the observations for computation, it is necessary to apply corrections for abnormal 
oscillations in the barometric column, which are caused by general movements in the atmos- 
phere, which are shown, by repeated and numerous observations, to extend rapidly and pro- 
gressively over large tracts of country. These corrections form a very important element in the 
computation of altitudes by the method of Lieutenant Abbot, and are obtained from simultaneous 
observations made at some fixed station in the vicinity of the field observations. 
The following tables of abnormal oscillations used in the correction of the observations made 
by Mr. Doty in May, 1854, between Fort Benton and Badger river, along the eastern base of the 
Rocky mountains, and for the observations made by Sergeant Lint in September, 1854, from 
Fort Benton across the Rocky mountains, by Lewis and Clark's Pass, to the Big Blackfoot, were 
obtained in the following manner: The observations made with the stationary barometer during 
the time occupied by the survey being all reduced to what they would have been if the mercury 
had been at 32? Fahr., a mean of all the observations taken at each particular hour was found, 
and the difference between this mean and any observation taken at the same hour was taken as 
the abnormal correction for the corresponding hour of the field observations. 
