PACIFIC EXPLORATION: C. F. MARVIN 
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extent. Little is known and much is as yet conjectured as to the real 
boundaries, dimensions, and characteristics of these several strata, 
even over land areas. Only an expedition like that proposed can suffice 
to extend such studies to our greatest ocean and over which there is 
every reason to suppose the atmosphere disposes itself in its best de- 
fined, simplest and most orderly arrangement because an ocean repre- 
sents an almost unlimited extent of level and uniform surface conditions, 
accompanied by stable and uniform gradients of temperature and other 
meteorological conditions. The modifying effects experienced at land 
stations due to their elevation above the sea, their local topographic 
environment, and other disturbing causes are wholly absent or inappre- 
ciable over the ocean, whence marine observation may be expected 
to supply, not only a kind of data the meteorologist greatly needs, 
but the best data of that particular kind. 
B)7 the aid of suitable recording instruments carried aloft by bal- 
loons we may obtain, if the instruments are recovered, a record of the 
temperature, pressure, and moisture of the air, the sunshine, and possibly 
some other conditions. However, as a free balloon simply drifts along 
with the air strata through which it rises and falls, no record of the 
motion of these strata can be procured from the balloon itself. To 
ascertain the motions we must continuously triangulate the successive 
positions of the balloons. This calls for two or more observers, with 
appropriate theodolites, located at the ends of a suitable base line. 
Such observations are often not even attempted as a part of aerological 
work, but they are indispensable in studies of the circulation of the 
upper air. No other observations are more urgently needed in meteor- 
ology at the present time than these, and it is difficult to conceive of a 
better field for conducting such observations on a broad and all-inclusive 
plan and scale than the Pacific Ocean. These motions of the free air, 
in conjunction with the pressure and temperature thereof, are the 
data most needed to verify or disprove, or rather, if possible, to adapt 
and apply Ferrel's general theories to the motions of the air as they 
may be actually observed on an expedition of the kind proposed. 
Emphasis has been laid upon the aerological work which a Pacific 
exploration could perform, because the need for this is greater, per- 
haps, than for any other phase of meteorological investigation, and 
also because the expedition provides such exceptionally favorable 
opportunities for its prosecution. Nevertheless, the complete study 
of surface conditions, the observation of clouds, fogs, waterspouts, 
auroras and lightning, including the photographing of such phe- 
nomena, and the intensive study of the inception, development, 
