INTRODUCTION. l v 



fully confirm the results obtained by the other vessels, cutting the 

 great Pacific Ocean in different directions. These need no explana- 

 tion. The diagram shows the route ; and the lines of reduced observa- 

 tions, which are marked with corresponding dates, point out the loca- 

 lity and result. 



MAP or AREAS OF TEMPEBATTJBE The map which faces the 

 title-page, is intended to point out the areas of temperature, embraced 

 in every 5 of temperature from that of perpetual frost up to the tem- 

 perature of 90, and above. The basis of this is found in the records of 

 the Expedition ; but in order to complete the areas, I have had recourse 

 to very many authorities, and in some cases I have been obliged to rely 

 upon observations by no means as satisfactory as I could wish, more from 

 the doubtfulness of the position, than the thermometric observations. 

 In consequence, it is only offered as a near approximation, in hopes 

 that attention may be called more fully to the subject, which may 

 afford an opportunity at some future day of perfecting it. On the 

 continents, the isotheral and isocheimal curves have been drawn in 

 preference to that of the isothermals, which latter give but little, if any, 

 idea of the climate. In an examination of this map, every one must 

 be struck by the great influence which the areas of ocean temperature 

 must have upon the continents : and, instead of looking entirely to the 

 continents (as has been hitherto done), to produce the phenomena of 

 temperature, and the ever-changing aerial currents, we should seek for 

 the causes in the vast areas of ocean, which are constantly radiating heat, 

 and which we see creating many disturbances in the perennial winds, 

 as well as in the atmosphere in all parts of the globe. And to what more 

 probable cause can they be assigned, than the influx of air to restore the 

 equilibrium over the vast areas of rarefied surfaces? From the re- 

 corded observations in this volume, many instances might be cited, 

 which would go to prove the influence that is exerted by these areas 

 on the winds, clearly pointing out their tendency towards their 

 centres; but my space will not permit my doing it here, and I shall 

 content myself with drawing the attention of observers more particu- 

 larly to the influences that the ocean areas of temperature may have 

 upon the climates, winds, and storms, that seem to emanate from, or 

 appear to be engendered by them. 



In concluding this Introduction, I must offer my acknowledgments 

 for the assistance I have received from Surgeon John L. Fox, and 

 Passed Midshipman John Wilkes, of the Navy, in preparing the tables 

 for the press, and to Mr. Joseph Drayton, superintendent of the draw- 



