54 PROCEEDINGS OF SECTION 4A. 
and D’Alembert, in his work on the precession of the 
equinoxes, had advanced the opinion that the fluidity of the 
sea took from it all influence upon this phenomenon.  La- 
place further examined the tidal oscillation of ,the atmo 
sphere, and found that the attraction of the sun and moon. 
cou:d not possibly produce the constant movement from east 
to west which we observe in the Trade winds, but that smail 
oscillations in the height of the barometer are produced 
whose: extent at the equacor he calculated at a half milli 
metre. 
All the work which has since been-done in the develop- 
ment of tidal theory has necessarily been based upon the 
grand fundamental work of Newton and _ Laplace. 
‘“ Amongst all che grand work which has been bestowed on 
this difficult subject,’ writes G. H. Darwin, “ Newton, not- 
withstanding his errors, stands out first, and next to him 
we must rank Laplace. However original any future con- 
tribution to the science of the tides may be, it would seem 
as though it must perforce be based on the work of these 
two.” 
Sir John Lubbock, in the years 1830 to 1840, did a great 
deal of work. in the way of co-ordinating and examining large 
masses of data obtained from English tidal observations. 
He was the first to introduce tite term “co-tidal line.” 
Afterwards Whewell constructed charts showing co-tidal 
lines, in general finding that these. lines meet the shore at 
very acute angles. The work of Lubbock and Whewell 
enabled trustworthy tide-tables to be computed for Brush 
ports. 
Airy wrote a very important review of tidal theory for the 
Encyclopedia Metropolitana, aud made most important con- 
tributions to the eee of the progress of waves along canals, 
and of the effect of friction upon the progress of the tidal 
wave. Amongst the many interesting results obtained by 
him, the follow ing, which refer to an * equatorial canal en- 
circling the earth, may be here noticed : — 
1. £f the depth of the canal be less than about i3 miles, 
and the water be considered frictionless. the attraction of 
the moon would cause low-water underneath the moon and 
high-water in the quadratures. This depth 1s such that a 
free wave would naturally take more than a day to go com- 
pletely round ; consequently, the tidal forces must be-so dis- 
tributed as to. continually hurry it on, so as to force it to get 
round in the time. This gives us the above disposition. 
2. if the depth of the canal were greater than about 15 
miles, in which case the free wave would naturaily oscillate 
