NARRATIVE OF THE CRUISE. 
885 
for as far as the present observations extend, the maximum inequality occurs from two to 
three days after the moon has attained its extreme north or south declination, and 
entirely disappears two or three days after the moon crosses the Equator. During the 
summer months the day tides are highest and have the greatest range, and during the 
winter months the night tides. Secondly, the atmospheric pressure, the range of which 
is very considerable in this locality, exerts a great influence on the mean sea level at the 
Falkland group, for it was found to rise and fall inversely as the barometric column, 
allowing a foot of water to be equivalent to an inch of mercury. It is therefore not at 
all improbable that occasionally during the winter months the residents at Stanley might 
observe, during the period of spring tides, a high Water that barely reached the ordinary 
mean level of the sea ; for if during this time of the year, when the day tides at springs 
have but a small range, a high barometer coincide with the period of greatest diurnal 
inequality, such a case would doubtless arise, and this has in all probability led the in- 
habitants to infer that a gradual alteration was taking place in the mean sea level. 
During the stay at the Falkland Islands from, January 23rd to February 6th, the 
mean temperature of the sea was 51° and of the air 48° '8. During Ross’s stay, from 
April to December 1842, the mean temperature of the sea was also invariably higher than 
that of the air, as the following table will show : — ■ 
Comparative Temperature of the Air and Sea for 1842. 
Month. 
Mean Temp, of Air. 
Mean Temp, of Sea. , 
Difference, 
May 
40-8 
43-5 
2° 7 
June 
34-1 
38/9 
4-8 
July 
33-8 
38-7 
4-9 
August 
344 
384 
4-0 
September 
38-9 
41-8 
2-9 
October 
November 
45-9 
47-4 
1'5 
In March 1833, Captain Fitz Roy in H.M.S. “ Beagle ” made the mean temperature of 
the air for the month 46°’7 and of the sea 48°‘7, and in March 1834, 46 0, 9 and 48°‘2, 
but in both these cases the temperature of the air is only given, as a rule, for noon of 
each day, so that this mean is higher than it should be. 1 
1 See Voyages of the “Adventure” and “ Beagle,” Appendix, London, 1839. 
