360 JOHN TEBBUTT. 
coincidence of the moon’s opposition with her passage through 
her perigee. In addition to these general conditions, I further 
pointed out that the moon nearly at the same time attained her 
‘greatest declination, namely twenty-four and a-half and twenty- 
three degrees in May 1880 and June 1889 respectively, and that 
the vertex or crest of the tide-wave therefore approached more 
than ordinarily near to the latitude of Sydney. But decisive as 
these maxima of declination were in producing the high tides of 
May 1880, and June 1889, they were not so potent as will be the 
corresponding condition at the next summer solstice. A little 
consideration will show that if at the time of the moon’s opposition 
at the summer solstice the longitude of her ascending node be 
approximately that of the vernal equinox, the moon’s north 
declination will be its greatest possible, and that as a consequence 
the crest of the tide-wave will also make its nearest possible 
approach to the latitude of Sydney. | 
In order that the members may understand at a glance the 
eminently favourable conditions which will obtain for a very high 
tide at next December full moon, I give them in the following 
table in juxtaposition with the similar conditions for the full 
moons of May 1880 and June 1889 :— 
1880. 1889. 1898. 
: d. h.m. de eheemr a. h. m. 
Full moon, Sydney mean time |May 24 444/June13 12 3/Dec. 23 2 41 
Perigee is 55 May 2416 O|Junel13 14 0)/Dec. 231 0O 
Moon’s opposition declination | —23" 39° | —21° 30' + 2825 a 
Sun’s declination at opposition) +20 51 ape 16) —23 27 
Moon’s distance at perigee in ; : 
equatorial radii of the earth } BOTTE poe 55°89 
I may add that the diurnal inequality of the high tides about 
the approaching solstice will be very great, and that it is the day 
spring-tide or that which occurs when the moon is below the 
horizon that we must look forward to as the extraordinary one. 
In the course of this paper I have referred to those conditions 
only which may be regarded as strictly astronomical, but there are 
