BAROMETER. 



BAROMETER. 



be observed to have its eyes closed as if 

 asleep. About sunset, the pair of owls, par- 

 ticularly when they have young, issue forth in 

 quest of food, and may be observed flapping 

 gently along, searching lanes, hedgerows, or- 

 chards, and small enclosures near outbuildings. 

 "In this irregular country," says White of 

 Selborne, " we can stand on an eminence and 

 see them beat the fields over like a setting dog, 

 and often drop down in the grass or corn.'' 

 Besides rats and mice, they feed on shrews, 

 small birds, insects, &c., and have sometimes 

 been known to capture and eat fish. It is said 

 of this owl, that when satisfied, it will hide 

 the remainder of its meat like a dog. The 

 barn owl lays from three to five eggs, which 

 are oval and white, measuring one inch six 

 lines in length, and one inch three lines in 

 breadth. Young birds are found from July to 

 September, and occasionally as late as Decem- 

 ber. The young birds are easily tamed, and 

 live in harmony with other birds. The barn owl 

 is common in most, if not all the counties of 

 England, and, according to Mr. Thompson, it 

 is also the most common owl in Ireland. In 

 Scotland, it is less numerous. Over the tem- 

 perate part of the European continent, and in 

 North America, it is generally diffused. Its 

 form and colour are too common to need de- 

 scription. The whole length of the bird is 

 about fourteen inches. ( Yarr ell's Brit. Birds, 



TOl. i.) 



BAROMETER. The word is derived from 

 two Greek words, which signify the measurer 

 of weight. This, the most valuable instrument 

 for meteorological observations in the farmer's 

 possession, was invented about the middle of 

 the 17th century, by Torricelli, an Italian phi- 

 losopher. Some observations of Galileo had, 

 perhaps, led the way to the discovery ; the at- 

 tention of this great philosopher, according to 

 a well known story, having been drawn to the 

 fact that water would not rise higher than 32 

 feet in a tube exhausted of air, by some work- 

 men of the Duke of Florence, who had vainly 

 endeavoured to construct a comon lifting pump 

 to raise water a greater height. Galileo ex- 

 plained the phenomenon, by saying that nature 

 had a horror of a vacuum, but that this horror 

 had its limits. It was found by Torricelli, that 

 a column of water of about 32 feet exactly 

 balanced the weight of the atmosphere which 

 surrounds our earth, and that this was equal 

 to the weight of a column of mercury of about 

 28 inches. Now this column of mercury, 

 under various outward shapes, forms the ba- 

 rometer, or weather-glass, so useful to the far- 

 mer. For as the pressure of the atmosphere 

 commonly varies with approaching changes in 

 the weather, the consequent rise or fall of the 

 mercury merety marks its amount : one end of 

 the mercurial tube is hermetically sealed and is 

 void of air, so that the quicksilver rises or 

 falls in it unresisted ; but the other end of the 

 tube is open, and the atmosphere forces the 

 mercury through this, by pressure on the sur- 

 face of the fluid mercury in the cistern. Thus, 

 th* atmosphere operates by its varying pres- 

 sure. When, therefore, the quicksilver r/.sv.v, 

 the atmospheric pressure is increasing ; when 

 It falls, the pressure is diminishing. 

 146 ' 



The more dense the state of the atmosphere, 

 the higher the mercury will rise in the instru- 

 ment. It is a popular notion that the atmos- 

 pheric pressure must be greatest when the air 

 is thick and cloudy. The term density, when 

 applied to the condition of the atmosphere and 

 its relations with the barometer, means specific 

 weight, without reference to its clearness or 

 cloudiness. Vapour or moisture in the air a.- 

 ways lessens its weight, and the more vapour, 

 whether this be invisible, or in the condensed 

 states constituting fogs and clouds, the less the 

 weight or density and pressure upon the ba- 

 rometer. 



It is more from this rising and falling of the 

 barometer, observes Mr. Forster, than from its 

 height or lowness, that we are to infer fair or 

 foul weather. In very hot weather the falling 

 of the mercury indicates thunder: in winter, 

 the rising indicates frost ; and in frosty weather, 

 if the mercury fall three or four divisions, 

 there will follow a thaw ; but in a continued 

 frost, if the mercury rises it will snow. When 

 foul weather happens soon after the falling of 

 the mercury, it will not continue ; and, on the 

 contrary, you may expect, if the weather be- 

 comes fair as soon as the mercury rises, that 

 it will be of short duration. In foul weather, 

 when the mercury rises much and high, and 

 so continues for two or three days before the 

 foul weather is quite over, then expect a con 

 tinuance of fair weather to follow. 



The words usually inscribed on the scale 

 plates of barometers, such as " Very Dry," " Set 

 Fair," " Fair," etc., etc., are extremely falla- 

 cious, and have tended to bring the instrument 

 into greafc discredit as a weather glass. We 

 may perhaps except " Stormy," for when the 

 lowest falls happen, they are always the pre- 

 cursors of very high winds and storms. The 

 words inscribed are, perhaps, better indica- 

 tions of the weather in England than on the 

 American side of the Atlantic. It must be 

 evident that when a barometer, with a scale 

 plate marked as usual, is carried to high 

 and mountainous positions, the mercurial co- 

 lumn falls, and has its relations with the words 

 on the scale plate entirely changed. The per- 

 son who wishes to make the barometer useful 

 in foretelling the changes of weather in the 

 United States must throw aside all dependence 

 upon inscriptions, with the exception mention- 

 ed, and study its fluctuations with reference 

 to the prevailing winds, dew-point, and other 

 conditions of the weather at the time. Rain or 

 snow is frequently preceded by a rise, instead 

 of a fall, of the mercurial column, and a fall 

 of the barometer often indicates the cessation 

 of rain. 



The rise in the mercurial column generally 

 indicates a northerly wind. The highest con- 

 ditions of the barometer in the United States, 

 near the Atlantic, commonly precede north- 

 easterly storms of rain and snow. The very 

 highest elevations have been attended Avith 

 very cold weather and a light wind from the 

 north, followed by snow or rain within forty- 

 eight hours. A subsidence of the mercury ge 

 nerally indicates wind from a southerly point, 

 and should this be so far round as to blow from 

 land, the fall of rain or snow will commonly 



