24.4) PROCEEDINGS OF SECTION A. 
water, and so is not apparent as a tide. At Boston Bay there 
are two tides with:a large diurnal inequality so marked as to 
make it sometimes appear that there is only one tide in the day. 
The absence at these ports of that intimate connection between 
the time of high water and the time of the moon’s passage across 
the meridian, which is so marked in the ports of the North 
Atlantic, is well brought out in the accompanying diagram. In 
this we have plotted curves, for Brest and for Port Adelaide, 
showing the nature of the changes in the interval between the 
moon’s meridian passage and high water on successive days at 
these ports. The ordinates to the curve are drawn at equal 
distances apart for successive tides, the length of the ordinate 
representing the interval. The lower curve represents the result 
in the case of Brest, and shows a regular wave lying wholly on 
one side of the zero line. When, however, we attempt to do the 
same thing with our Port Adelaide tides we find that instead of 
getting a periodic curve the interval shows a continuous progres- 
sion, as is exhibited on the same diagram by the upper curve. 
In fact we have not the same number of tides in a month as there 
are transits of the moon. 
No. 7.—NOTES ON THE VERTICAL COMPONENT OF 
THE MOTION OF THE EARTH’S ATMOSPHERE, 
AND- A WIND-VANE, SHOWING VERTICAI 
MOTIONS OF THE AIR. 
By Masor-GenersL Scuaw, C.B. 
(Read January 10, 1898. ) 
