518 



PROTECTION AOAINST INSOLATION. 



decomposition on the surface of the ground shelter the roots 

 of trees from the sun. 



(e) Density of Crop. — Woods in which tlie trees stand some- 

 what far apart from one another suffer more from drought 

 than well-stocked woods. Isolated, clean-boled standards 

 with smooth bark, such as beech, hornbeam, birch, silver-lir, 

 especially at noon, reflect the rays of the sun on to the soil, 

 as shown in Fig. 242, and thus dry up the soil around them ; 



young natural - regeneration 

 may fail completely around 

 such trees. 



(/) Weatlicr and Season of the 

 Year. — The drying-up of little 

 plants owing to drought may 

 be recognisable early in the 

 summer. A dry May with a 

 continuance of cutting east 

 winds soon disperses the 

 moisture in the soil that has 

 accumulated during winter, and 

 if there is insufficient rain 

 in June, many plants on areas 

 recently sown or planted may 

 be killed. If tlie dry weather 

 should continue throughout 

 July, more damage will be 

 done, and it is generally from 

 the middle of July till the 

 plants die, for the maximum 

 summer - temperature is attained at about a month after 

 Midsummer-Day. 



Not until the beginning of September, therefore, can young 

 plantations and sowings which have hitherto escaped be 

 considered out of danger from drouKht. 



middle of August that the 



3. Jief/isler of l)ri/ ]'((irs. 

 Dui'ing the past century, the following have been years of 

 drought in Central Europe : 1800, 1807, 1811, 1812, 1822, 1834 

 1812, 1840, 1857, 1858, 1851), 18(33, 1805, 1808, 1874, 187(), 



