Mr William Galbraith on the Tides. 241 
_ By the Nautical Almanac, to this time we shall have,— 
The sun’s semidiameter, r= oe 17°3 
declination, G—2a So 7300S: 
The moon’s semidiameter,o= 0 16 44°6 
declination, O6=19 28 53:0S. 
To these values of r and p, we have froin the table,— 
Dena +... 941164 ‘Log 644 1 Wlp.ggaes 
d =23 13 30 cos? = 992660 8 =19 28 53 cos? = 994880 
f =02179 log 9:33824 f'=0'8155 log 9-91143 
f = 08155 
F = 1-0334 
1:0000 
F-1= 00334, the excess of this tide above unity. 
Hence, 0:0334 x 5°08 = 0-169672 foot. Wherefore, 5:08 + 0:17 
= 5:25, consequently this tide would rise to 5:25 feet only above 
the mean level of the sea, or 0°17 foot (about 2 inches) more than 
the usual spring-tide, when the sun and moon are on the equator, 
_ and at their mean distance from the earth. Whence the whole rise 
___ from low water to high water would be 5-25 x 2=10-5 feet on that day, 
independent of the state of the barometer and force of the wind. In 
similar circumstances, the greatest effect would be (Ainslie’s Survey- 
ing, 398), 5°08 + 5:08 x 0:178= 5:08 + 0:90 =5-98 feet, and twice 
this, that is, 5-98 x 2=11-96 feet, or nearly 12 feet, the total rise 
from low to high water, when the sun and moon exerted the greatest 
possible influence (a very rare occurrence), independent of the effects 
of the wind and state of the barometer—phenomena that cannot be 
_ predicted. The foolish exhibition made at many of our sea-ports on 
that day, will be long remembered.* 
Indeed, in tropical climates, the effects of hurricanes and tornadoes 
_ are so great, that they occasionally raise the sea to such a height as 
to carry large ships over sand-banks, and up a low flat country, as was 
_ the case a few years ago with regard to the York Indiaman, of about 
1200 tons burden, which, I was informed by one of her officers, 
_ was carried over the Sauger Sands and driven over land, so far as 
to be left high and dry at some distance from the usual sea-shore, 
; * If great precision be required, especially when the wnit of height is con- 
_ siderable, the correction must either be repeated or the true quantity found by 
i: proportion, thus :— 
1, As 083: 1 :: 4:34: 5°23 feet—u. 
2. As 1 10334 :: 5:23 : 5:40 feet = rise. 
_ which are the true quantities, whereas the preceding are only near approxima- 
_ tions if not repeated. 
VOL. XLVIII. NO. XCVI.—APRIL 1850. Q 
