THE BOTTLE-TIT 31 



vapour-laden current, striking our chilly shores, or 

 raised by high cliffs or mountains to a colder level, 

 suddenly parts with its heat, loses its hold on its 

 burden of vapour, which becomes visible or tangible 

 in the condensed form of mist, rain, or snow. Then 

 and this is the important point the heat till now 

 employed in carrying vapour is released from its 

 task and goes to raise the temperature of the air. 



The influence of rainfall upon temperature is 

 hardly suspected even by those exposed most con- 

 stantly to its effects. Dr. Haughton affirms that one 

 gallon of rainfall gives out enough latent heat to 

 melt seventy-five pounds of ice or forty-five pounds 

 of cast-iron, and that on the west coast of Ireland 

 the heat derived from rainfall is equivalent to half 

 that derived direct from the sun. 1 



XI 



In this long strip of wood facing the western 

 sea, the windward trees are grotesquely ^ 

 dwarfed. The outmost ash and sycamore Bottl e-tit 

 are aged dwarfs, from four to eight feet high ; and 

 though the trees not exposed directly to the blast 

 rise to loftier proportions, yet the tops in the whole 



i Physical Geography, p. 126. 



