Wellington Philosophical Society. 171 



itself. This inertia belongs to molecules as much as to masses. While the 



of the molecules is diminished, and the distance between the undulations 

 is increased, the actual force, which we call heat, remains undiminished. It 

 is only necessary that the undulations should be again crowded together in 

 order that the energy may be restored. 



So far I hope that I have made my meaning clear, — that air in taking up 

 moisture loses sensible heat. No one who has travelled on the West Coast of 

 the South Island can have failed to notice when he leaves the forest road, and 

 comes on the dreary sands of the coast, with a moderate sea breeze, how 

 miserably cold the air is in the immediate vicinity of the breakers. This is 

 owing to absorption of sensible heat by the solution of the spray in the current 

 of air sweeping over the sea. 



Next, in reference to the heat gained, if any, in the passage of the air over 



W 



Plains. 



:ains 



from the direct radiant heat of the sun, for the rarefied air is, to use a technical 

 expression, almost transparent to the sun's heat rays — it permits them to pass 



very slight loss. The 



It is not 



so, however, with the heat radiating from the surface of the ground — this is 

 almost entirely absorbed by the atmosphere, which thus gains sensible heat 

 until at length it reaches the eastern slopes of the mountain ranges. 



Here, where the column of air begins its descent to the plains, we ought 

 to have a complete reversal of every phenomenon that accompanied its passsage 

 from the level of the sea on the West Coast till it reaches the elevation of the 

 mountain ranges. As the column of air sinks down, the increased extent of 

 the vertical column gives increased pressure, and compresses more and more 

 the lower stratum — the latent heat becomes sensible and the thermometer 



rises. 



should 



adds to the energy 



raseology, converts the latent heat into heat recognised 



senses 



Airy has explained that when the 

 id, the changes of temperature of 



the aii- are very great : — " Upon s 

 We have verified the experiment 



jylinder in which a piston fits tightly and 



before 



uii 



inflame the tinder." And Airy remarked, "in the powerful air pum 

 by large steam engines) which were used to exhaust the air tubes 

 atmospheric railway, that when the attenuated air in the tube, having 

 the temperature of the ground, was compressed by the operation of 



