WEA 



WEA 



for the weaned lambs. The clover, 

 or the sainfoin, or the after-nialh are 

 selected by some ; otiiers put their 

 smaller and more weakly lambs to 

 weed the turnip crops ; but there can 

 be notiiing more desirable than a fresh 

 pasture, not too luxuriant, and yet 

 sufficient to maintain and increase 

 their condition." — (Yuuatt on Sheep.) 



WEAR. A fence or dam made of 

 twigs and set in a stream. 



WEATHER. " The state or condi- 

 tion of the atmosphere with respect 

 to heat, cold, dryness, moisture, wind, 

 rain, snow, fogs, 6cc. The apprecia- 

 tion of the various causes wliich de- 

 termine the state of the atmosphere, 

 and produce those changes which are 

 incessantly takmg place in its condi- 

 tion, and wiiich are popularly called 

 the weather, forms the subjects of 

 Meteorology and Climate. (See those 

 terms ; also, Almosphere, Barometer, 

 Cloud, Dew, Hail, Rain.) 



" In all ages of the world, mankind 

 have attempted to explain and prog- 

 nosticate the changes of the weather ; 

 but such is the complication of the 

 subject, and the vast multitude of 

 circumstances to be taken account 

 of, that no theory can furnish rules 

 for determining the order in which 

 they succeed each other, or for pre- 

 dicting the state of the weather at a 

 future time, with any approach to cer- 

 tamty. Nevertheless, all the difler- 

 ent modifications of the atmosphere 

 are the necessary results of princi- 

 ples not only fixed and unalterable 

 in their nature, but (many of them at 

 least) well known in their separate 

 and mdividual operation. The diffi- 

 culty of tracing the results of their 

 combined influences arises chiefly 

 from their complexity and endless 

 concatenation. 



'• The principal cause of all the va- 

 riations which take place in the state 

 of the atmosphere is the heating ac- 

 tion of the sun's rays ; but in order 

 to appreciate correctly its effect, it is 

 necessary to know not only the ex- 

 tent of the atmosphere, but the prop- 

 erties of all the substances of which 

 it is composed. Modern science has 

 discovered that the atmosphere is 

 83S 



composed of three different gaseous 

 fluids, everywhere combined in the 

 same proportions, and penetrated by 

 an ever-varying quantity of elastic 

 vapour. These two distinct enve- 

 lopes of air and vapour mechanically 

 mixed have different relations to heat ; 

 and therefore, in c()nsc(iuence of the 

 unequal temperature of the surface 

 of the earth, with which they are in 

 contact, they cannot both be in a 

 state of equilibrium at the same time. 

 In consequence of the diurnal rota- 

 tion, the different parts of the atmo- 

 sphere are constantly receiving differ- 

 ent quantities of heat, as the solar 

 rays penetrate more or less obliquely. 

 This inequality of temperature pro- 

 duces winds, which, if the surface ot 

 the earth were perfectly regular and 

 homogeneous, would always blow ia 

 the same direction ; but the surface 

 of the earth being composed of ma- 

 terials of various kinds, and irregu- 

 larly disposed, the distribution of heat 

 over it is extremely irregular. The 

 winds, sweeping along the surface, 

 acquire its temperature ; and hence 

 the atmosphere also becomes irregu- 

 larly heated. This produces an ac- 

 cumulation of air at one place, and a 

 deficiency at another ; and hence a 

 subsequent rush to restore the equi- 

 librium. As the air is cooled it be- 

 comes also incapable of holding the 

 same quantity of aqueous vapour, a 

 portion of which is therefore set free, 

 and gives rise to clouds, mist, rain, 

 dew, snow, &c. Besides all this, 

 there is to be taken into account the 

 development of electricity ; the influ- 

 ences of light and galvanism ; the agi- 

 tation of the atmosphere produced 

 by the rise and fall of the tides ; and 

 probably a variety of other circum- 

 stances with which we are entirely 

 unacquainted. This very imperfect 

 enumeration may serve to give an 

 idea of the difficulties to be overcome 

 in forming a theory of the weather. 



" It has always been a favourite 

 prejudice that the weather is influ- 

 enced in some mysterious manner by 

 the moon. The moon can be sup- 

 posed to act on the earth only in oue 

 of three ways ; namely, by the light 



