xvi INTRODUCTION TO THE SIXTH EDITION. 



A separate chapter is now devoted to the Land and Sea Breezes, 

 and extensive contributions have been made to that on Monsoons, 

 Trade Winds, and Cyclones. Lieutenant Jansen, of the Dutch 

 Navj, has helped me to enrich these with his fine thoughts. The 

 reader will, I am sure, feel, as I do, deeply indebted to him for so 

 much instructive matter, set forth in his very delightful and pleas- 

 ing manner. 



National Observatory, Washington, April, 1856. 



Since the above date, explorations have been made in this in- 

 teresting department of science, and new veins of precious ore have 

 been hit upon. We have not yet gone deep enough into them to 

 justify a final report ; a preliminary one is given in the Addenda. 



In 1849 Congress passed an act requiring the Secretary of the 

 Navy to employ three small vessels in assisting me to perfect my 

 discoveries. A few weeks ago, Lieutenant Berryman put to sea 

 in the " Arctic" on this duty. His attention was especially direct- 

 ed to deep-sea soundings along the great telegraphic plateau 

 stretching from Newfoundland to L-eland. The results, so far, 

 are of the highest interest. Among them is the discovery of a line 

 of volcanic cinders along a line a thousand miles in length, and 

 reaching entirely across the Gulf Stream where the submarine 

 telegraph is to cross it. 



There is also among the Addenda Lieutenant Jansen's exper- 

 iments upon Ozone, which cast unexpected light upon the circu- 

 lation of the atmosphere. 



Matter of more general or higher scientific importance than that 

 contained in these Addenda is seldom gathered from any fields of 

 research. 



December, 1856. 



