10 INTRODUCTION. 



to remain beneath the water much longer than those 

 creatures whom he imitates. 



This dress, by the way, is not so modern an inven- 

 tion as is generally thought, although its present state of 

 perfection is necessarily owing to the modern improve- 

 ments in machinery. In the Ambras Collection there 

 is a manuscript of the fifteenth century in which are 

 represented several men in diving dresses, and fur- 

 nished with stoppered vessels of air, which they can 

 breathe when needed. It is true that the value of 

 compressed air for respiratory purposes was not known 

 at the time, and that a single vessel could only contain 

 air sufficient for two or three respirations. The 

 principle, however, had been recognized, and its 

 further development was only a work of time. 



As to fire, it has at present baffled us, and all 

 that we can do is to delay its conquering powers. 



There still remains the Earth, into which man is 

 becoming daily a more accomplished trespasser, his 

 powers in this respect increasing, together with his 

 civilization. The savage never troubles himself about 

 penetrating into the earth any more than he does 

 about rising into the air. He may make use of a cave 

 by way of a habitation ; but there he stops. Whereas 

 civilized man must needs act the trespasser in the 

 domains of earth, as he does in those of air and 

 water. He digs mines, which descend to vast depths, 

 and traverses the earth with a network of subterranean 

 galleries. 



Or, dissatisfied with the mountains that divide 

 one district from another, just as he is dissatisfied 

 with separating seas, he drives his tunnels through 



