WEE 



WEE 



which it reflects ; by its attraction ; or I 

 by an emanation of some unknown ' 

 kind. Now, the light of the moon I 

 does not amount to the 100,000lh part 

 of that of the sun ; and the heat which I 

 it excites is so small as to he alto- ' 

 gether inappreciable by the most del- '< 

 icate instruments, or ilie best devised 

 experiments. No efl"ect can be at- 

 tributed, therefore, to the moon's 

 light. With a regard to the attrac- 

 tion of the moon, we see its influence ; 

 on the tides of the ocean, and might ' 

 therefore be disposed to allow it a | 

 similar influence on the atmosphere ; 

 but when we take into account the 

 small specific gravity of atmospheric 

 air in comparison with water, and the ; 

 consequent smallness of the mass of, 

 matter to be acted upon, it will read- [ 

 ily be perceived that this influence 

 also must be extremely feeble. In ' 

 fact, it has been demonstrated by La- j 

 place that the joint action of the so- 1 

 lar and lunar attraction is incapable ! 

 of producing more than an atmospher- | 

 ic tide flowmg westward at the rate j 

 of about four miles a day, and con- 

 sequently scarcely, if at all, appreci- 

 able. As to the remaining supposi- 

 tion, that the moon may act on the ' 

 atmosphere by some obscure emana- ■ 

 tion, it is sufficient to remark that no 

 meteorological observations that have 

 yet been made afibrd the slightest ; 

 traces of any such connexion be- 

 tween the earth and its satellite. The 

 registers which are now kept in va- , 

 rious observatories and other places 

 also prove, contrary to the popular 

 belief, that the changes of weather 

 are in no way whatever dependant 

 on the lunar phases." 



WEATHER-BOARDING. Board- 

 ing naded either upright or horizon- 

 tally, and lapping on the outside of 

 the framing. 



WEATHER GLASS. See Barom- 

 elcr. 



WEDGE. One of the simple me- 

 chanical powers, the efficiency of 

 which is proportional to the length 

 of the side. Knives are wedges. 



WEED S. " Every plant which 

 grows in a field other than that of j 

 which the seed has been sown by the 1 



husbandman is a weed, and, inas- 

 much as it interferes with the in- 

 tended crop, should be carefully erad- 

 icated. It is a proof of good culti- 

 vation when few weeds appear among 

 the growing crops, and many of the 

 operations of tillage are mtended 

 ciiiefly for their destruction. One of 

 tlie principal uses of summer fallows 

 is to destroy the weeds which come 

 up in spring, and which would shed 

 their seeds in summer if they were 

 not destroyed before the seeds ripen. 

 When roots are sown in drills and 

 carefully hoed, they produce the 

 same cleansing efTect, and supersede 

 the fallow ; but in heavy loams which 

 have been neglected and overrun 

 with weeds, a clean fallow is some- 

 times indispensable, before any im- 

 proved method can be adopted. When 

 a farmer enters on lands which are 

 in a foul state, it is the cheapest 

 way, in the end, to sacrifice a crop, 

 and thoroughly purge his fields from 

 weeds, especially those which have 

 vivacious roots, and cannot be extir- 

 pated by simple ploughing. The 

 mode of doing this must depend on 

 the nature and duration of the weeds, 

 whether their roots are perennial, or 

 die off after the plant has borne seed. 

 Annual weeds are most readily ex- 

 tirpated by repeated harrowings, by 

 which the seeds are brought within 

 the influence of the atmosphere, and 

 when they have fairly vegetated may 

 be buried or rooted out, and by ex- 

 posing their roots to the influence of 

 a hot sun they are effectually destroy- 

 ed. The seeds of annual weeds are 

 chiefly brought on the land in the 

 manure which is made in the yards, 

 where the cattle fed on hay or straw 

 swallow the seeds, which pass 

 through them undigested. By exci- 

 ting a great degree of fermentation 

 in the mixture of dung and litter 

 some of the seeds may be destroyed, 

 but many of them will keep their 

 vegetative powers even after having 

 been exposed to a considerable heat ; 

 and as it is not advisable to let the 

 manure undergo a great degree of 

 decomposition before it is carried on 

 the land, many seeds always escape 



839 



