1839] 



and Set of the Tides at Madras. 



139 



C would be perpendicular ; and corresponding to any given angle 

 of inclination, it might readily be computed what was the velocity of the 

 current: the rod E C being situated m the water, it was necessary to 

 attach an index D B (whose inclination could be read olf with the posi- 

 tion micrometer attached to tlie 5 feet telescope). 



The Times proper for making the observations were next to be consi- 

 dered ; with regard to the tides, the observations on the days near to the 

 new and full moon and at the quarters w^ere evidently the most pro- 

 per ; and for the set of the sea, those days in which the surf was higher 

 than usual should evidently be adopted ; hence I selected the days fol- 

 lowing the 1st, 2d, 3d and 4th quarters of the moon, when hourly obser- 

 vations from 6 A. M. to 6 p. m. should be regularly registered, and on any 

 intermediate days in case of a higher surf than ordinary. 



The Run of the Sea has been measured by taking the difference be- 

 tween the greatest and least angles of depression of the iron buoy No. 

 1, which (as has been already stated) was anchored in l8 feet water with 

 18 fathoms of cable ; these differences being reduced into feet, are as 

 follows : 



1838 



Remarks. 



6h. 



7h. 



8h. 



9h. 



lOh. 



lib. 



12h. 



Ih. 



2h. 



3h. 



4h. 



5h. 



6h. 







F.I. 



F.I. 



F.I. 



F.I. 



F. I. 



F. I. 



F. I. 



F.r. 



F.I. 



F.I. 



F.I. 



F.I. 



F.I, 



October 16 



Rough sea 













4 9 

















26 













4 3 







5 3 





4 3 







27 



Squally 





4 6 



4 9 



4 4 



4 4 



4 9 



4 9 



4 9 



4 9 



4 9 



4 1 



3 6 



4 4 



November 3 



4 7 



3 4 3 2 3 2 



3 2 



2 4 



3 4 



4 1 



4 1 



3 4 2 9 



3 9 





10 



Very calm 











1 9 



2 2 

















19 





3 2 3 4 



3 0 



3 2 



3 2 



2 7 



3 2 



3 2 



3 2 



2 4 



2 4 





26 







2 2 2 4 



2 2 



2 4 



2 0 



2 2 



2 4 2 6 3 2 



3 0 



3 2 





December 3 



High surf 





4 714 7 



4 7 



4 7 



5 0 



5 0 



4 7 



4 7 



4 3 



5 0 



5 0 





On the morning of the 6th December the sea and surf had risen to an 

 unusual height, but the only remaining buoy having been washed on 

 shore, I was unable to make further observations. The difference in 

 height between the summit and lowest point of the breakers could not 

 have been less than 8 or 10 feet. Breakers or surf extending f mile 

 from the shore. 



The Velocity of the Current. — It was my intention, to have mea- 

 sured the velocity of the current by the " Indicator^^ as already ex- 

 plained ; but, either the iron work was not sufficiently strong, or it 

 offered too great a temptation to some thievish catamaram man, — for the 



