OF ARTS AND SCIENCES : OCTOBER 10, 1865. 



33 



In connection with these results are given in the following table those 

 obtained by Dr. Bache from the discussion of the tides at Key West, 

 Florida, and published in the Coast Survey Reports, and also in Silli- 

 man's Journal (Second Series, Vol. XVIII. p. 305). They have been 

 reduced from English feet to meters for convenience of comparison with 

 the preceding results. The second numerical column contains the vari- 

 ations of atmospheric pressure at Havana, which is used for computing 

 the corrections at Key West due to that cause. The coefficient of the 

 astronomical term for Key West is -J- .005. The corrections and the 

 corrected results are also given in the following table : — 



For the convenience of comparison the following graphic representa- 

 tion of the results for the two ports is given, the first and third curves 

 representing the annual variation of mean level at Brest and Key West 

 respectively, uncorrected for the effects of the astronomical term and 

 the variation of atmospheric pressure, and the second and fourth the 

 corrected results. The curves are somewhat irregular, because the 

 number of both tidal and barometric observations is not great enough 

 to eliminate all the accidental and other irregularities ; but the dotted 

 curves, cutting off small irregularities, although somewhat arbitrary, 

 must very nearly represent the true results. 



With regard to the effect of the winds in changing the mean level of 

 the sea, either at Brest or Key West, little is known, but it is evident 

 from various researches at other ports, that they can have but little 

 effect, except for very short periods during heavy gales, and therefore 

 cannot cause much change in the monthly means, or the means of the 

 different seasons. M. Dausy concluded from his researches that the 

 mean level of the sea was not sensibly altered at Lorient by breezes 



VOL. VII. 5 



