No. XIX. ABSTRACT OF TIDAL OBSERVATIONS. 



361 



The space between a a and a! a' represents the Lunar 

 Parallactic Tide deduced from Spring tides, and the space 

 between b b and b' b' represents the Lunar Parallactic Tide 

 deduced from Neap tides. 



The range of the Lunar Parallactic Tide deduced from each 

 is sixteen inches. 



The curves A A and b b show the semiannual variation of 

 the Lunisolar fortnightly tide cleared of lunar parallax. 



II. 'Alert.' Cape Sheridan. 



The apparent Lunitidal interval (full and change of 

 moon) observed on board the ' Alert ' was — 



22 h 37 m . 

 The following table shows the relation which the apparent 

 Spring and Neap tides bear to the calculated Semidiurnal 

 Spring and Neap tides, and shows, as before, that the chief 

 tide is the Semidiurnal : — 



Maximum Spring and Minimum Neap Tides. — Range in Inches. 



