THE CURRENTS OF THE ATLANTIC. 



409 



parts of the coast-line of Ireland, are as follow, the deaths from all 

 causes being 1000 : 



North-east, from Glenarm to Dublin, . . 

 South-east, from Dublin to Youghal, . . 

 South, from Youghal to Bantry Bay, . . 

 South-west, from Bantry Bay to Galway, 

 North-west, from Galway to Donegal Bay, 

 North, from Donegal Bay to Glenarm, . 



172 



161 



106 



76 



83 



127 



The proportion of the highest of these numbers to the lowest is 

 nearly that of 2 to 1. 



I have hitherto spoken only of the relation of the temperature 

 of the air to health : it remains to say a few words of its moisture. 



We all know that the outer covering of the human body is 

 porous, and that these pores are incessantly engaged in the per- 

 formance of an office, upon the due discharge of which the health 

 is closely dependent ; but we are perhaps not all aware of the 

 magnitude of the operation. The experiments of Lavoisier and 

 Seguin show that the quantity of water, which transudes through 

 the skin of an average-sized man, in 24 hours, is 30 ounces ; and 

 this, in the ordinary state of things, is carried off by evaporation 

 as fast as it is secreted. Now, it is a well-known meteorological 

 law, that evaporation is less, the greater the amount of moisture 

 actually present in the air ; and that it ceases altogether when the 

 air is saturated with moisture. It follows, therefore, that the due 

 performance of one of the most important functions of the animal 

 system is dependent on the dryness of the air. It is not to be in- 

 ferred from this, however, that the transpiration, as Blumenbach 

 denominates the process, ever wholly ceases, even when the air is 

 saturated with moisture. For the air in contact with the body 

 rises in temperature, and is thus enabled to take up a fresh supply 

 of moisture from the skin. 



But besides the effect of humidity in checking the process of 

 the insensible perspiration, it also operates in reducing the animal 

 heat, when the temperature of the air is low. This seems to re- 

 quire some explanation. One of the immediate consequences of 

 evaporation is, we know, the abstraction of heat ; and as the eva- 

 poration from the surface of the body is less in moist air than in 



