288 LIGHT SCIENCE FOR LEISURE HOURS. 



about 40 south latitude we find the same pressure as 

 at the equator, and thence a more rapid diminution. 

 The rate of change is illustrated graphically in Fig. 1, 

 which represents the height of the barometer above 

 28 J inches for different southern latitudes. In the 

 northern hemisphere there is a similar increase of 

 pressure as we leave the equator, a maximum is there 

 also attained in about latitude 30 ; but from this 

 point towards the poles there is a marked difference in 

 the rate of diminution of pressure in the two hemi- 

 spheres. The following table by Schow is sufficient to 

 indicate this : 



North latitude Barometric pressure 



29-853 in. 



10 30-002 



20 30-004 



30 30-069 



40 30-006 



45 30-011 



60 29943 

 55 - 29-960 



60 29-835 



65 29-623 



70 29-722 



75 29-863 



There are minor irregularities in this table, due, 

 doubtless, to local peculiarities, the arrangement of 

 land and water being so much more complicated in the 

 northern than in the southern hemisphere. Neglecting 

 these (as in Fig. 2, which represents for the northern 

 hemisphere the relations corresponding to those exhibited 

 for the southern hemisphere in Fig. 1), we see that 

 there is a much greater resemblance between the rise 



