2 METEOROLOGICAL RESULTS OF LAST CRUISE OF CARNEGIE 
sis of the similarity of sea-surface temperatures; that 
is, consecutive days of similar sea-surface tempera- 
tures have been placed in one group. The mean positions, 
number of days, and dates included by these groups are 
presented ir table 1, and the eighteen areas defined by 
the periods have been plotted in figure 3. Three groups 
(numbers VII, XIII, and XVII) have been subdivided into 
seven subgroups (VIla, VIIb, XIIla, XIIb, XVIIa, XVIIb, 
and XVIIc) owing to the fact that the Carnegie spent two 
or three periods in each of these areas. 
Acknowledgments 
A complete enumeration of all those who generously 
offered advice and assistance in carrying out the mete- 
orological program of the Carnegie, and who aided in 
bringing this work to its final published form, would 
hardly be possible. No report of the meteorological 
work of the Carnegie, however, should fail to mention 
Dr. J. H. Paul, the observer-in-charge of the meteoro- 
logical program of cruise VII of the Carnegie, for his 
painstaking care in obtaining and recording data; Dr. 
H. U. Sverdrup, who began the compilation of data, for 
his constant assistance throughout all stages of the work; 
Dr. C. F. Brooks, for his many helpful suggestions; Dr. 
J. Bartels, of Germany, who, during a year as research 
associate with the Department of Terrestrial Magnet- 
ism, also gave advice and directions concerning the in- 
terpretation of results, particularly with reference to 
the chapter on atmospheric pressure; and finally, Dr. 
J. A. Fleming, Director of the Department. Apprecia- 
tion is also due the staff members of the Department of 
Terrestrial Magnetism and the faculty of the University 
of California, Scripps Institution of Oceanography, for 
their interest and assistance. 
La Jolla, California 
September 21, 1937 
ATMOSPHERIC PRESSURE 
INSTRUMENTS AND METHODS 
Barometers 
Throughout the entire cruise the Carnegie carried 
two barometers, one mercurial and one aneroid. A stand-: 
ard marine mercurial barometer of the Kew type (U.S. 
Weather Bureau No. 7272) was mounted in the chart 
room of the vessel, 3.96 meters from the port rail, 6.25 
meters from the starboard rail, and 1.98 meters above 
load water line. A scale error of -0.409 mm was deter- 
mined by the Instrument Division of the U. S. Weather 
Bureau in April 1928. The corrections for temperature 
and gravity were made according to the formula 
[-0.0001634 /(1+ 0.0001818t)] 760t+ a 
where t. is the reading of the attached thermometer and 
a is a variable correction for gravity dependent on lati- 
tude. Whereas the mercury readings were corrected on 
board for temperature, height above the sea (+0.20 mm), 
standard gravity, scale errors, and capillarity, there is 
no record of control observations between this instru- 
ment and mercurial barometers at the ports visited. It 
was impossible to determine whether any change in the 
correction constants had occurred during the cruise by 
obtaining a series of control observations at a later date, 
inasmuch as most of the instrumental equipment, includ- 
ing the barometer, was destroyed when the vessel burned 
at Apia, Western Samoa. 
Mercurial barometer observations were made daily 
at noon GMT, and the height of the mercury column was 
read to the nearest 0.1 mm. Each observation usually 
consisted of twenty distinct readings, the mean of the 
twenty being taken as the final value. On days when con- 
siderable ‘‘pumping’”’ of the mercury was evident, how- 
ever, aS many as forty readings were taken, and every 
effort was made to obtain an equal number of readings at 
the bottom and top of the “‘pumping range.’’ Theattached 
thermometer was read at the beginning and end of each 
series of mercury readings, and the mean of the two was 
used for obtaining the correction for temperature effect. 
A Paulin type aneroid barometer (no number) was 
suspended in the chart room approximately 3.4 meters 
above load water line and was used by the various ob- 
servers in atmospheric electricity, pilot-balloon work, 
and navigation. This instrument was compared daily at 
noon GMT with the standard mercurial barometer. The 
differences between the two instruments seldom ex- 
ceeded 0.5 mm, but when the air temperature fell much 
below 10°, the sensitivity of the aneroid was considera- 
bly decreased, apparently because of the thickening of 
the castor-oil lubricant. No doubt this difficulty would 
have been eliminated if the instrument had been thor- 
oughly cleaned by immersion in benzine and all traces 
of oil removed from moving parts. This barometer, 
however, was not used for routine pressure observations, 
and consequently these errors are of little significance. 
Barograph 
The barograph, a sylphon-vacuum-chamber type 
with seven-day clock movement constructed by Julian P. 
Friez and Sons, of Baltimore, was mounted on a shelf in 
the cabin approximately amidships and 1.07 meters 
above load water line. The barograms were graduated 
to read from 715 mm to 795 mm, and the time scale was 
changed in such a manner that the values of pressure 
could be read at every full hour, local mean time. The 
corrections to be applied to the hourly readings of the 
barograph were computed from the corrected standard 
mercurial readings at noon, and the differences between 
barograph and corrected barometer readings at this 
hour each day were plotted directly on the barograms 
and curves drawn through these points. If the pressure 
changes during the week were irregular, an average cor- 
rection for the week was Computed and applied as a cor- 
rection to the hourly values for that week, but if the 
curve of differences showed a regular change, owing 
either to a buckling of the paper or to a shift in position 
on the drum, the correction to be applied to each hourly 
value was obtained directly from the plotted curve of 
differences. 
