142 



THE OCEAjN". 



time, and we may state that from the temperate to the equatorial 

 zone the curves of the shore increase in regularity. The innumer- 

 able ports which penetrate deep into the northern lands, are suc- 



Fig. 51.— Filled-ui) Fjords of Christianssaud. 



ceeded in the south by more and more inhospitable maritime shores, 

 because of destitute indentations. And on the coasts of the torrid 

 zone, which are destitute of the mouths of rivers, vessels must sail 

 along for hundreds of leagues before finding a harbour of refuge. 

 It is the three southern continents, South America, Africa, and 

 Australia, which present in their outline a most uniform development 

 of coast and are most destitute of bays. 



If we can rightly consider each glacier as a natural thermometer, 

 indicating by its advance and retreat all the changes of local tem- 

 perature, we may in the same way regard the general character of 

 the coasts, from the fjords of Greenland and Norway to the long 

 shores of equatorial Africa, as a visible representation of the changes 

 of temperature which have taken place on the surface of the globe 

 since the glacial epoch. If by long and patient study we succeed in 

 measuring the time which is necessary for the alluvium of the sea 

 and rivers thus to modify the forms of valleys once filled with 



