220 



THE TIDES. 



stances, the tides are also affected by the state of the atmosphere. At Brest, 

 the height of high water varies inversely, as the height of the barometer, and 

 rises more than eight inches for a fall of about half an inch of the barometer. 

 At Liverpool, a fall of one tenth of an inch in the barometer corresponds to a 

 rise in the river Mersey of about an inch ; and at the London docks, a fall of 

 one tenth of an inch corresponds to a rise in the Thames of about seven tenths 

 of an inch. With a low barometer, therefore, the tide may be expected to be 

 high, and vice versa. The tide is also liable to be disturbed by winds. Sir 

 John Lubbock states, that, in the violent hurricane of January 8, 1839, there 

 was no tide at Gainsborough, which is twenty-five miles up the Trent a cir- 

 cumstance unknown before. At Saltmarsh, only five miles up the Ouse from 

 the [lumber, the tide went on ebbing, and never flowed until the river was dry 

 in some places ; while at Ostend, toward which the wind was blowing, con- 

 trary effects were observed. During strong northwesterly gales the tide marks 

 high water earlier in the Thames than otherwise, and does not give so much 

 water, while the ebb tide runs out late, and marks lower ; but upon the gales 

 abating and weather moderating, the tides put in and rise much higher, while 

 they also run longer before high water is marked, and with more velocity of 

 current : nor do they run out so long or so low. 



