58 PROCEEDINGS OF SECTION A. 
In places where the apparent irregularity has been sc 
great as to make the work of tidal prediction. quite hopeless 
by older and simpler methods, the accurate results obtained 
by the use of harmonic analysis have proved after all that 
‘the complexity of the motion was distinguished by a won- 
derful order. 
Extreme accuracy in tidal prediction is out of the ques 
tion, on account of the effect of wina and barometric 
pressure upon the height of the water. In calm weather, 
and with a steady barometer, tidal predictions should be 
accurate, but these conditions seldom exist. A committee of 
the British Association, appoimted to investigate the effect 
of wind and atmospheric pressure on the tides, reported in 
1896, after examining the tidal records of several British 
ports, that the height of the tides is affected by wind in 
about one case out of four, and that a variation of half an 
inch from the average barometric pressure causes a variation 
of sbout 15 inches in the height of the tide. They further 
reported that, although, as far as average results go, there 
can be traced a direct connection between the force and 
direction of the wind and the variation in the height of the 
tides; yet, that there is so much discrepancy in the average 
resuits, when applied to individual tides, that no reliable 
formula can be established for indicating the amount of 
variation in the height of the tide due to any given force of 
wind. Irregular actions of the wind will not affect the 
accuracy of an analysis, because, im averaging up over an 
extended period—-such as one year—-such actions will be 
practically eliminated. Regular diurnal meteorological 
effects, which are very marked in some places, will show 
themselves as a part of the ordinary solar tide. In spite, 
however, of irregular meteorological actions, which it is im- 
possible to forecast, the predictions based upon this system 
are quite sufficiently accurate for practical purposes. At 
Port Adelaide, where the tides are very complex, by far the 
greater number of predictions have a smaller error than 
10 minutes in tyme and 6 inches in height. . During last 
year, out of 1348 predictions, 1022 were correct to less than 
10 minutes. 
Vidal prediction is the direct practical application of Har- 
monic Analysis, but is by no means the only reason for its 
being carried into effect. The analysis of tidal records at 
various places on the earth’s surface may be expected to 
gradually furnish us with information as to the way in which 
the tidal wave travels over our oceans, such as we can get 
by no other means. Where tidal forces have uninterrupted 
