12 JUNGLE ISLAND 



earth that hid the rocks underneath, so that it 

 was impossible to tell how long to expect them to 

 keep sliding down into the Canal. The engineers 

 sent for a geologist, a man who had studied rocks 

 and knew their history, to come down from the 

 United States and help them decide which were 

 solid enough to make safe canal banks and which 

 could not be trusted. 



The geologist studied the cut hillsides and bored 

 down to rock in other parts of the Isthmus. He 

 was able to give advice to the canal builders, so 

 that the Canal could be safely made. He found, 

 too, stories of the Isthmus long before the 

 Spaniards or the Indians came. 



The rocks showed that some of them had first 

 been poured out from volcanoes, red-hot and soft 

 as molasses. After they had cooled, the wind 

 and rain had weathered them into smaller pieces, 

 the sea water had poured over them and left the 

 skeletons of little sea animals strewn among 

 them, and the rivers had washed valleys through 

 them again and again. 



The rocks showed plainly that the Isthmus 

 has not always been solid land as it is today. 

 Often it has sunk under the sea until its mountain 

 tops were only a chain of islands between North 

 and South America. 



This is one reason why the South American 

 animals are so different from those in North 

 America. For many thousands of years at a 



