84 THE WONDERFUL CENTURY. 



to serve as centres of condensation at considerable alti- 

 tudes, and thus to initiate rainfall when the other con- 

 ditions are favorable ; but the presence of increased quan- 

 tities of dust at the lower levels must lead to the forma- 

 tion of denser clouds, although the minute water-vesicles 

 cannot descend as rain, because, as they pass down into 

 warmer and dryer strata of air, they are again evapo- 

 rated. 



!N"ow, there is much evidence to show that there has 

 been a considerable increase in the amount of cloud, and 

 consequent decrease in the amount of sunshine, in all 

 parts of our country. It is an undoubted fact that in 

 the Middle Ages England was a wine-producing coun- 

 try, and this implies more sunshine than we have now. 

 Sunshine has a double effect, in heating the surface soil 

 and thus causing more rapid growth, besides its direct 

 effect in ripening the fruit. This is well seen in Canada, 

 where, notwithstanding a six months' winter of extreme 

 severity, vines are grown as bushes in the open ground, 

 and produce fruit equal to that of our ordinary green- 

 houses. Some years back one of our gardening period- 

 icals obtained from gardeners of forty or fifty years' 

 experience a body of facts clearly indicating a compara- 

 tively recent change of climate. It was stated that in 

 many parts of the country, especially in the north, fruits 

 were formerly grown successfully and of good quality 

 in gardens where they cannot be grown now; and this 

 occurred in places sufficiently removed from manu- 

 facturing centres to be unaffected by any direct deleteri- 

 ous influence of smoke. But an increase of cloud, and 

 consequent diminution of sunshine, would produce just 

 such a result; and this increase is almost certain to have 



