70 Mr. H. H. Howorth on 



and have thought it best and most honest to state each 

 man's views in his own words. The general argument and 

 arrangement are of course my own. 



As we rise in the atmosphere the cold increases and we 

 speedily reach a height when the temperature is always 

 below the freezing point of water all the year round. It is 

 clear that above this line no rain falls, but only snow, and 

 further that this snow when it falls remains in the condition 

 of snow, and does not melt, except a thin superficial layer 

 due to the influence of the direct rays of the sun, which is 

 very slight. Above this line, then, not only does the snow 

 remain as snow, but also as dry snow, and in a loose, 

 powdery condition, on which no ordinary pressure will alter 

 its structure or convert it into ice. This is the case on the 

 higher Himalayahs and the Andes. Below this line the 

 temperature is at some seasons of the year above the 

 freezing point of water, and the snow is consequently more 

 or less melted annually, and is also in a more or less 

 damp and moist condition. This line, therefore, marks 

 an important frontier in the meteorological features of the 

 high-lands. 



Let us now turn to another such frontier, namely : the 

 line separating the zone where all the snow which annually 

 falls is melted away and that in which only a portion of 

 it is melted : this is known as the snow line. This line 

 varies in height according to the latitude. At the Equator 

 it is about 16,000 feet above the level of the sea, and it sinks 

 to about the sea level near the Poles. Above the snow line 

 and below the line where the temperature is always under 

 the freezing point of water, a certain portion of the snow 

 which falls annuall}' is melted by the summer heat, while 

 another portion gradually augments in thickness from 

 the snow line upwards. Tyndall describes one portion of 

 the process in his usual graphic manner : " The sun first 

 raises the superficial snow to 32° and then melts it. The 



