1 8 SCIENTIFIC RECREATIONS. 



the specimens, will complete his outfit. We amused ourselves by having 

 these instruments made by the blacksmith, sometimes even by manufacturing 

 them ourselves ; they were simple, but solid, and admirably adapted to the 

 requirements of research. Often we directed our walks to the seashore, 

 where we liked to collect shells on the sandy beach, or fossils among the 

 cliffs and rocks. I recollect, in a walk I had taken some years previously 

 along the foot of the cliffs of Cape Blanc-Nez, near Calais, having found an 

 impression of an ammonite of remarkable size, which has often excited the 

 admiration of amateurs ; this ammonite measured no less than twelve inches 

 in diameter. The rocks of Cape Grisnez, not far from Boulogne, also afford 



Fig. 12. Group of rock crystal. 



the geologian the opportunity of a number of curious investigations. In the 

 Ardennes and the Alps I have frequently procured some fine mineral speci- 

 mens; in the first locality crystallized pyrites, in the second, fine fragments of 

 rock crystal (fig. 12). I did not fail to recount these successful expeditions 

 to the young people who accompanied me, and their ardour was thereby 

 inflamed by the hope that they also should find something valuable. It 

 often happened when the sun was powerful, and the air extremely calm, that 

 my young companions and I remarked some very beautiful effects of mirage 

 on the beach, due to the heating of the lower strata of the atmosphere. 

 The trees and houses appeared to be raised above a sheet of silver, in which 

 their reflections were visible as in a sheet of tranquil water. It can hardly 

 be believed how frequently the atmosphere affords interesting spectacles 



