134 THE MICROSCOPE. 



of these positions, stands higher in this calm 

 region than it does either to the north or south ; 

 a proof, Maury remarks, of the banking up of 

 the atmosphere here from the meeting of the 

 two currents, and of pressure from its downward 

 motion. 



The imaginary northern particle having pass- 

 ed the calm belt of Cancer, now moves on the 

 surface, as the north-east trade wind. As such 

 it proceeds until it arrives near the equator. 

 Here it meets a similar hypothetical particle 

 which has started from the south pole at the 

 same time that the other left the north pole, 

 and which blew as the south-east trade wind. 

 Again then, there must be another collision of 

 winds a pressure against each other, and an- 

 other calm (" the belt of the equatorial calms"). 

 Thus these two hypothetical particles pause in 

 their course ; then, warmed by the heat of the 

 sun, they begin to ascend. Our imaginary par- 

 ticle (from the north) travels in the upper re- 

 gions (counter to the south-east trades, which 

 blow at the surface below), until, in nearly 30 s. 

 latitude, it meets another particle from the south 

 pole. As before, they must contend, then pro- 



