418 On the hifluence of Atmospheric Pressure on the 



As regards the influence of the winds on the mean level upon 

 the south coast of Cornwall and Devon, Mr Walker observes, 

 that east and west winds scarcely affect it, but that southerly 

 winds raise the sea above it from one to ten inches, and off- 

 shore winds depress the water beneath it as much, according to 

 their force. On the morning of the 29th November 1836, 

 when the velocity of the wind was estimated at about 100 feet 

 per second, the sea at Plymouth was raised three feet six and 

 a half inches above the mean level, the greatest height above 

 the equilibrium level he has seen. The hurricane began at 

 S.W., and the barometer was very low ; therefore this great 

 increase in height is due both to the wind and diminished at- 

 mospheric pressure. A gale of wind from the southward, a low 

 barometer, and a high spring -tide concurring, cause damage 

 and inundations on the southern coast of Cornwall and Devon. 

 From the form of the Bristol Channel, and the absence of a 

 free passage for the waters, such as exists at the Straits of 

 Dover, in the English Channel, westerly winds force up and 

 sustain a great body of water, thereby raising the sea above 

 the mean level several feet. It appears from an account of the 

 great storm of the 26th November 1703, that the tide flowed 

 over the top of Chepstow Bridge, inundating all the low lands 

 on both sides of the Severn, washing away farm-yards, drown- 

 ing cattle, &c. ; and it is worthy of remark, that the barometer 

 is recorded to have then fallen lower than had ever been pre- 

 viously noticed. 



It will be obvious that, while in a hurricane such as that of 

 November 1836, noticed by Mr Walker, the level of the sea 

 was raised on the south coast of Cornwall and Devon ; it was 

 also depressed on the north coast of those counties ; so that 

 the difference in the sea-level on the two coasts thus caused, 

 would be the sum of the elevation and depression produced on 

 each coast respectively. It will also be obvious, from the form 

 of the Bristol Channel, that the sea-level on the two coasts will 

 not be the same with westerly winds, and the difference will be 

 in proportion to the force of such winds. With easterly winds 

 also, this level will be disturbed ; for, while such winds act as 

 an off-shore wind in the Bristol Channel, forcing the waters 

 outwards, on the south coasts of Devon and Cornwall there 



