INTRODUCTION. 



9 



gress of science, and I cannot but think that our 

 yearnings for aerial travelling will one day be satisfied, 

 and that railways will be to the aerial carriages what 

 waggons are to railways. 



We pass to another element namely, the water, 

 in which man also becomes a trespasser. 



The simplest and most natural mode of trespassing 

 in this element is by swimming ; and every swimmer 

 knows the exultant delight with which he lies rocked 

 in the heaving waves, or dives through the curling, 

 white-topped breakers with as much security as if he 

 were reclining on a feather-bed at home. Still further 

 does he trespass by the act of diving, and exults in his 

 power of penetrating into the depths of the sea, and 

 defying, though for a short time, the power of the 

 water. 



As he progresses in civilization, he is propor- 

 tionately dissatisfied with his natural powers of 

 trespassing, and resorts to art, The log becomes a 

 raft, is modified into a boat, and soon is magnified into 

 a vessel. The wind is pressed into the service of man, 

 and aids him to propel his vessel by means of sails. 

 At last, dissatisfied with a vessel that is dependent 

 upon the wind, and anxious to be able to trespass upon 

 the ocean at his own will, man applies the power of 

 steam to his ship, and so becomes independent of 

 wind, tide, or any other obstacle to his progress- 



Nor is he yet satisfied. It is not enough to 

 trespass upon the surface of the water. He wishes to 

 emulate those air-breathing creatures which are enabled 

 to spend most of their time beneath the surface, and 

 contrives, by means of diving-bells and diving- dresses, 



