362 BAROMETER. 
“9, A wind blowing upward or downward 
would affect the pressure of the air. Thisisa 
cause whose existence we have proved in the case 
in question. Its effect upon the mean pressure 
of the air in the equatorial regions is unequivo- 
cally maintained in the Instructions for the Bri- 
tish scientific expedition to the Antarctic regions, 
recently prepared by the President and Council 
of the Royal society, causing the barometer at 
the equator to stand permanently lower than in 
latitude 30°, by about a quarter of an inch. The 
ascending current of December 20th, 1836, could 
not, however, exert any direct influence upon the 
barometer, except near the centre of the storm. 
To account for the entire oscillation, I think, we 
must admit another principle quite distinct in 
its operation.” 
Professor Loomis then comes to his final pre- 
sumed cause: he says,— 
“10. Let a wind blow ever so violently over 
the earth’s surface, and the diminution of gravity 
arising from the centrifugal force must be incon- 
siderable. But, imagine the different parts of 
| the current to travel with unequal velocity, and 
there will arise 2 mechanical condensation or 
rarefaction. When air is at rest, or in motion, 
with a uniform velocity, its particles are main- 
tained at a constant distance from each other. 
But let the velocity of one section be increased 
beyond that of the succeeding, and the same 
particles of air are forced to fill a greater 
space. Such is the principle of the undulations 
which produce the sensation of sound. It ap- 
pears to me that a similar effect must have been 
produced in the storm of December 20th, 1836. 
| The south-east wind which accompanied the rain, 
moved with an accelerated velocity. The particles, 
therefore, of air at one extremity of the current 
must have left those at the other extremity at 
an increased distance. Hence a mechanical 
rarefaction, and, of course, diminished pressure. 
The reverse effect must have taken place after 
the storm had passed. A north-west wind sets in 
with great violence. A vast body of air is pre- 
cipitated towards the south-east. The partial 
vacuum which at first existed is very soon sup- 
plied. Yet though the first impelling cause has 
ceased to act, the momentum of the excited cur- 
rent still urges it onward. The front of the wave 
is impelled by the momentum of the mass in the 
rear, and a mechanical condensation results, 
bringing, of course, increased barometric pres- 
sure. The cause, however, which produces this 
extraordinary rise, being temporary in its na- 
ture, soon ceases, and the barometer falls. The 
causes which I have here assigned for the oscil-’ 
lation of the barometer appear to me to be such 
as are known to be true, and that they are suffi- 
cient to account for the phenomena.” 
Mr. Green, the celebrated aéronaut, comment- 
ing on the hypothesis of Professor Loomis, in an 
article in the ‘ Journal of Meteorology,’ says,— 
“J now give my reasons why these causes do 
BARREN EARTH. 
not appear to me to be ‘ sufficient to account for 
the phenomena.’ 
“ist. The circumstance of different parts of 
a current of air having different velocities obtains 
very frequently, and is almost always observed 
by aéronauts, and, indeed, is known to be almost 
always the case, 1 may say. For at sea we set 
light sails aloft, and expect them to catch the 
breeze well, when it remains very gentle below. 
Hence we ought to have diminished pressure on 
all such occasions, which we do not. 
“2d. Professor Loomis mentions that ‘ winds 
may commonly be referred to one of the three 
following causes: viz., Ist, Inequality of atmo- 
spheric pressure ; 2d, Unequal specific gravity of 
air; 3d, Rotation of the earth.’ And here we 
find ‘ inequality of atmospheric pressure’ given 
as the leading cause of wind, while we have seen 
wind given, in another place, as the cause of in- 
equality of atmospheric pressure. This seems to 
me a circular argument, and I scarcely know how 
to find a beginning. I agree, however, with the 
Professor, that when there is diminished pres- 
sure, ‘ the same particles of air are forced to fill 
a greater space. And the question is, ‘ What 
causes them so to do?’ I reply, that the pre- 
sence of powerful electric currents passing from 
the earth into the atmosphere will produce this | 
effect. And the consideration of it fails to pre- 
sent a difficulty which occurs in Professor 
Loomis’s hypothesis, but which I omitted to de- 
scribe. I allude to the fact that the decrease of 
pressure occurs long éefore the storm of wind, 
and, therefore, it cannot be any difference in the | 
velocity of the gases moving in the atmosphere 
which causes that decrease ; because the effect is 
seen before the guas? cause exists.” 
BARREL. A cask, or a small, long, narrow 
cylinder. A barrel of beer or ale legally con- 
tained, in former times, a quantity equal to 325 
imperial gallons; but it now contains 36 imperial 
gallons. The word barrel was formerly a frequent 
commercial term of measure, and very widely 
varied in capacity according to the particular 
nature of the commodity. A barrel of anchovies 
was 50 lbs.; of barilla or potash, 200 lbs. ; of gun- 
powder, 1 cwt.; of herrings, 32 gallons; of nuts, 
3 bushels; of oil, 314 gallons; of raisins, 1 cwt.; 
of soap, 260 lbs.; and of ship beef or pork, 200 
Ibs. A barrel, in popular language, is any small, 
long, narrow cylinder, such as the tube of a 
fowling-piece or the body of asmall cask. Water- 
tight and air-tight iron barrels, coated with 
composition, have for some time past been used 
in the navy, and might be serviceable to the 
farmer. 
BARREL DRAIN. See Dratn. 
BARREN CORN. See ABortive Cory. 
BARREN EARTH. The unstirred subsoil of 
any land which has long been in cultivation. 
But the term as thus applied, though of frequent 
occurrence in old books on agriculture, is a gross 
misnomer. Some subsoils, indeed, contain very 
