Factors Influencing Plant-Life on Sandy Sea-shores. 49 
that of the atmospheric strata immediately above during fall and 
winter, and a considerable amount of heat is at that time absorbed 
by the air. 
On tropical and sub-tropical coasts the variations in temperature 
of sea water are mainly due to change in the direction of wind and 
to currents. A series of observations made in 1901 on the east coast 
of Australia, near Brisbane, gave the mean temperature of the 
surface water during January, that is the hottest month of the 
southern hemisphere, as 22-4° C., in February 21'l 0 C., in March 
20- 6 n C., and in April 19‘2 n C. The mean atmospheric temperature 
during the same periods was respectively 27'2, 25'4, 24*3, and 
21- 6 n C. The highest daily variation observed was from 20 , 6"C. at 
8 a.m. to 23’5° at 6 p.m. on February 11th, with a corresponding 
change of atmospheric temperature from 29‘2 to 324. After a 
prolonged period of continuous westerly winds, the temperature of 
the surface water fell three degrees, while it always rose after 
northerly and fell after southerly winds, the former bringing warm 
water from the tropics and the latter cold water from the south. 
Close to the shore or where the water is shallow, the temperature 
of the water is higher when the surface is calm, but low where the 
sea is rough. This is the natural consequence of the solar radiation 
in the former case, and of the mixing by the waves of the surface 
water with the colder water from below when the sea is disturbed. 
The observations upon which the present paper is founded 
were made during a period of years on many sea-shores in Europe, 
Asia, Australia, South Sea Islands and North and Central America. 
Special attention was paid to the coasts of the Baltic and the east 
and west coasts of Australia, A dune district near San Francisco 
in California was studied in detail. 
BIBLIOGRAPHY. 
Andresen, C. C. Om Klitformationen og Ivlittens Behandling og Bestyrelse. 
Kiobenhavn, 1861. 
Bosch, R. B. van den. Vergelijking van de vegetatie dec duinstrecken om 
Calais met die van Nederland. Ned. Kruidk. Arch. v. IV., 
pp. 209-212, 1858. 
Briggs, Lyman J. The mechanics of soil moisture. Bull. 10. Division of 
Soils, U.S. Department of Agriculture, 1897. 
,, Salts as influencing the rate of evaporation of water from 
soils. Report 64, U.S. Dept. Agric., 1900. 
