TIDAL OBSERVATIONS. 207 



91. It is extremely interesting to find that, althougli the lunar and 

 solar semidiurnal tides are very small in value, the series of means from 

 which they were obtained were extremely regular and good, and the conse- 

 quent determination of the phase of spriag-tides from their respective epochs 

 is pi'obably correct within a few minutes. The proportion between the am- 

 plitudes of the lunar and solar semidiurnal tides is the nearest to equality 

 j'et obtained, being in the ratio of 11 to 6. The comparatively large value 

 of Rj of Series S is undoubtedly a genuine tide, but the smallness of the cor- 

 responding value of Scries M must forbid the conclusion of its beiug purely 

 astronomical. It is perhaps produced by temperature or wind, its time of 

 maximum being about 40 minutes after noon. There are also indications of 

 a similar and large annual tide of 0-3 foot amplitude, and maximum about 

 July, which is also pi'obably meteorological in its origin. The proportion 

 between the lunar and solar diurnal (Declinational) tides (E, of Series 

 and P) will be, on the assumption of the variation of E^ of Series being as 

 the square of the sine of the declination, about 4 to 1. 



92. The following are the values of the long-period tides which have been 

 obtained since the Edinburgh Meeting : — . ' 



R e 



ft- o 



Solar annual tide (elliptic and meteorological) ... o'274 i44'5o - 



Solar semiannual tide (declinational and meteoro- 

 logical) o'i28 3S'o- 



Lunar niontlily tide (elliptic) o'io6 304*17 



Lunar fortnightly tide (declinational) ©•043 i36'69 



Luni-solar fortnightly tide (synodic) 0*099 336-26 



The above epoch for the solar annual tide would place tlie maximum about 

 August 16. 



