Item 50 - Letter from George Airy

3 pp.

Royal Observatory Greenwich - Christie has sent him Belcher's observations at Tahiti: 'The solar tide there from whatever cause, is almost exactly equal to the lunar tide (April & May 1840), & that at quadratures the tide disappears'. GA gives his opinion of WW's distinction between an unlimited canal and a re-entering canal: 'In the formation of the differential equations there is no difference whatever (the laws of fluids, as regards transmission of pressure and the effect of pressure and external force on motion, applying in both cases to every point of the fluid: and this being all that the differential equations express). In the solution of the differential equations there is no difference except this - that, in the nature of the thing, it is impossible to permit solutions in the reentering canal which are not periodical in the completion of the circuit of the canal. There is however usually no temptation to introduce such, because the expression for the forces (on which the distinctive function in the solution must depend) are necessarily periodic in the completion of the circuit'. GA outlines some of the complications involved with the distinctive function (and arbitrary function) and the type of canal.