370 rnYSICAL GEOGRArHY OF THE SEA, AND ITS METEOROLOGY. 



691. Tlie barometric descent of the monsoons. — Each monsoon, 

 like the trade-winds, blows from a higher to a lower barometer. 

 Taking tip the clew from this fact, and resorting again to the 

 graphic method for illustration, we may ascertain, with consider- 



Diagram C. 

 22° 20" l!T. 15° l.at 10° 



able accuracy, not only the relative strength of the north-east 

 and south-west monsoons of the sea, but also the mean height of 

 the barometer in the interior of India during the south-west 

 monsoon, supposing that monsoon to go no farther than the 

 mountain range, which may be taken at a mean to be about the 

 parallel of 30° north. Now, taking the mean height of the 

 barometer at the equatorial calm belt to be (§ 362) 29.92 inches ; 

 the mean height in the calm belt of Cancer to be 30.21 inches, 

 the line N.E. of the Diagram D will represent the average baro- 

 metric declivity of the north-east monsoons generally. The mean 

 height of the barometer during the three months of June, July, 



