1904-1905.] 337 



side of the mountain over a considerable area. The ancient 

 pine forest had utterly disappeared in Ireland, and could 

 only be seen in the British Isles in two or three localities in 

 Scotland; and some idea of its nature could be formed from 

 a slide giving a view of the pine forest at Ballochbuie, near 

 Balmoral. Mr. Henry then entered into the causes underly- 

 ing the division of the earth's surface into woodland, grass- 

 land, and desert. The broad generalisation could be made 

 that the amount of rainfall was the determining factor. 

 Where the rainfall was scanty the desert condition prevailed. 

 Trees required immense quantities of water to replace what 

 they transpired into air, and, being deep-rooting plants, they 

 found it in the subsoil in all localities where the rainfall was 

 considerable, and there they ousted the grass. The greater 

 the rainfall the denser the forest and the taller the trees. 

 Soil was a subsidiary factor; the rainfall determined the 

 existence of the forest, the soil determined the kind of tree. 

 In Southern Russia, in the most fertile soil, now devoted to 

 wheat cultivation, no trees occurred ; there were formerly 

 only the grassy steppes. The cause was the small rainfall — 

 Less than 20 inches Cold in itself was not the cause of 

 absence of tree growth. The northern pole of cold is located 

 in the Siberian forest. Cold drying winds in winter put a 

 stop, however, to tree growth, as trees then transpiring water 

 could not replace it from the frozen ground, and died of 

 drought. On the higher parts of lofty mountains dryness 

 and not cold was the cause of the absence of trees. Ireland 

 had an ideal forest climate, there being a heavy rainfall, and 

 in winter a mild temperature, with an absence of cold drying 

 winds. In ancient times the forests of Ireland were very 

 luxuriant, and evidence of this was forthcoming in various 

 ways — historical records, remains of peat mosses, submerged 

 coast forests, &c. Trees grew astonishingly well in Ireland 

 at the present day. The lecturer showed slides of remarkable 

 trees in different parts of Ireland — the tallest ash, which 

 reaches 130 feet in height, in Kilkenny; the biggest chestnut, 

 in Wicklow; great silver firs, &c. What was more remark- 



