563 
of Edinburgh, Session 1868 - 69 . 
numerous registers of temperature kept in vessels exploring the 
north-west passage, complete the lines for North America. In 
Asia the observations made at Russian government stations in 
Siberia in the north, at the ports of China and Japan on the east, 
at the Dutch Colonies in the East Indies, and in British India on 
the south, give the direction of these lines with certainty. For 
Africa we have the returns of numerous French stations in Algeria 
and Marocco, from Egypt, from the colonies on the Guinea Coast, 
from Cape Colony and Natal on the south, and a few checking 
points from the observations of travellers in Central Africa and 
Abyssinia. In South America the ascertained points are fewest; 
but observations made at the ports on both sides of the continent, 
from Panama to Patagonia, those of Ross in the Falkland Islands, 
a collection of temperatures in the Argentine Confederation given 
in the work on -that country by M. Maitin de Moussy, along with 
a few isolated points in Brazil, enable the range lines to be drawn 
here also with confidence. Lastly, for the coasts and south-eastern 
part of the interior of Australia, and for New Zealand, we have a 
large number of observations made chiefly by the Colonial Govern- 
ment. On the charts shown the parts of the earth’s surface which 
have a less annual range than 40° have been tinted in red , the 
strength of the colour increasing as the range diminishes ; and 
those regions which have a greater range than 40° in blue , the depth 
of colour increasing with the range. 
At the point where January and July, the coldest and warmest 
months of the northern hemisphere, turn to January, the warmest, 
and July, the coldest month of the southern hemisphere, we find a 
line passing round the globe on which there is no difference be- 
tween the temperatures of these two months. 
Starting from the first meridian we find this zero line passing 
along the Guinea Coast of Africa, through the centre of that con- 
tinent, bent northwards by the table land of Abyssinia, and again 
by the Indian Ocean, entering India below Bombay and running 
curiously down the line of the Western Ghauts to Cape Comorin ; 
then by the south of Sumatra through Java to New Caledonia, 
and across the Pacific between the parallels of 10° and 20° south 
latitude to the South American Coast, which it meets between lati- 
tude 5° and 10° south. Now it passes northwardly along the line 
