REPORT ON HYDRAULICS. — PART II. 493 



London Docks averaged a level of 1*5 inch higher, and ten 

 minutes earlier time, than at the lower side of London Bridge ; 



2nd, The low water of spring tides at London Docks averaged 

 a level of three inches lower, and nine minutes earlier time, than 

 at London Bridge ; 



3rd, The high water of neap tides at London Docks averaged 

 a level of one inch higher, and eight minutes earlier time, than at 

 London Bridge; 



4th, The low water of neap tides at the London Docks aver- 

 aged a level of two inches lower, and fourteen minutes earlier 

 time, than at London Bridge. 



It was found also. That high water of the highest spring tides 

 occurs at three or four o'clock, and high water of neap tides at 

 eight or nine o'clock : 



The flow of the spring tides is from four to five hours ; and 

 the ebb from seven to eight hours and half : 



The high water of spring tides produced an average fall 

 through London Bridge of eight inches, but the greatest fall up- 

 wards was 1 • 1 inch : 



The low Avater of spring tides produced a fall of 4*4 inches 

 through the bridge ; but the greatest fall was 5*7 inches : 



The high water of neap tides through London Bridge upwards 

 produced a fall of 5 inches : 



At the low water of neap tides the fall upwards was 2*1 inches j 

 but the least fall at low water was 1*1 inch. 



It appeared also, That it took forty minutes after low-water 

 spring-tides to produce slack water under the bridge with a 

 flood tide ; two hours with a flood of neap, and with an ebb 

 spring tide thirty minutes after high water, and fifteen minutes 

 after an ebb of neap tides : 



That the time of high water was about ten minutes earlier at 

 London than at Westminster Bridge : 



That the mean low-water line has a fall of — 



4-0 in. from Westminster to Waterloo Bridge ; 7 min. later at Westminster 



than at Waterloo Bridge. 

 4-3 do. from Waterloo to Blackfriars Bridge ; 6 ditto. 

 3-2 do. from Blackfriars to Southwark Bridge ; 5 ditto. 

 0-5 do. from Southwark to London Bridge ; 4 ditto. 



