IV PREFACE. 



For the benefit of readers who may wish to see the 

 latter problem analytically treated, I have given in an 

 Appendix the substance of Sir Greorge Airy's investi- 

 gation. 



In this second edition, I have introduced some correc- 

 tions and further elucidations, but have omitted the 

 Appendix. The subject of the first part of this Essay 

 has been treated with more detail by the late Dr. Samuel 

 Haughton in a paper entitled " Mathematical Principles 

 of Tidal Theory and Observation," published in Her- 

 mathena, 1879, p. 563. The present Essay has been 

 translated into Italian by Professor Edoardo de Ferrari, 

 of Empoli. 



