56 I Proceedings of the Royal Society 
of the Andes to Quito, and curves round the whole north coast of 
South America to beyond the mouth of the Amazon, then down 
into the South Atlantic to include the island of Ascension, which 
has a northerly range, and again northwards to the 20th parallel 
of north latitude, where it enters the African continent. It is 
observed that this zero line is very far from coincident with the 
mathematical equator of the globe, and that the parts of it which 
pass through the great land masses are in the northern hemisphere, 
in Africa, India, and South America, whilst those which pass 
through the Atlantic and Pacific Oceans are carried far into the 
southern hemisphere. 
The line of 10° of range in the northern hemisphere passes 
through the centre of North Africa above Lake Tchad, is carried 
to the north by the influence of the Red Sea to beyond Djedda on 
its east coast, round the west and south coasts of Arabia, through 
Aden, and thence to India near the Gulf of Cutch. Here it 
reaches southward, taking the form of the peninsula, to beyond 
Madras, then crosses the Gulf of Bengal to Further India, 
passes round the coast of Cochin China and through the Philip- 
pine Islands in latitude 10° north, then turning to the north-east, 
keeps in this direction through the Pacific till it enters North 
America above the parallel of 40° north latitude ; from that it 
turns down the coast of California to near the south of Mexico at 
Vera Cruz, through the West Indies just to the northward of Cuba, 
and across the Atlantic, with a northerly bend towards the Azores, 
to the African coast in latitude 25° north. 
The line of 20° range in the northern hemisphere is one of the 
most interesting of all, since it shows in the most marked manner 
the difference of range between the west and east coasts of the 
continents. It passes through North Africa and Southern Asia, 
carried to the north at the Red Sea and Persian Gulf, leaves the 
east coast of Asia at Macao, near Hong-Kong, in 15° north latitude, 
runs well into the Pacific, keeping away from the Asiatic coast, and 
reaches the American west coast in latitude 55° north, or 40° further 
to the north than where it left the Asiatic coast, then it turns 
south to Mexico, across the north of the Gulf of Mexico to Florida, 
leaves the east coast between latitude 25° and 30° north, then into 
fhe Atlantic to the Bermudas, after which, bending due north-east, 
