132 ON ATMOSPHERIC AND BAROMETRIC 



Sabine, it is stated, that " the land wind declines 

 till about ten o'clock a.m. at which time the 

 direction of the aerial current changes, and there 

 is generally a lull of an hour, or an hour and a 

 half's duration. The sea breeze then sets in, 

 the ripple on the surface of the water indicating 

 its commencement, being first observed close in 

 shore, and extending itself gradually out to sea. 

 The sea breeze is freshest from two to four, and 

 progressively declines in the evening hours." 



According to this, as well as other accounts 

 which need not at present be given, we may then 

 say, that soon after ten o'clock in the morning, 

 some cause comes into operation that makes atmos- 

 pheric pressure less over the land, than it is over 

 the sea, and therefore a portion of the air flows from 

 the sea to the land, — from where the pressure is 

 greater to where it is less. This disturbance of 

 the equilibrium of atmospheric pressure has been 

 represented as arising from the sun heating the 

 surface of the land more than that of the sea. 

 But if this were the cause in the case just given, 

 the sea breeze ought to have set in earlier, seeing 

 that the thermometer at Bombay, near the surface 

 of the earth, rose much more before half-past ten 

 o'clock in the morning, than it did after that time. 



