v i INTRODUCTION. 



duplicates, and occupying three times the space they now fill in this 

 volume; and although it might have given a fuller idea of the duties 

 performed by the officers of the Expedition, yet it would have been 

 of no advantage commensurate with the expense that would have 

 been incurred. 



The Meteorological Eegisters that were kept in connexion with the 

 Expedition at Cambridge, Mass., by Wm. Cranch Bond, Esq., Astro- 

 nomer, Harvard College, and at the naval depot, Washington City, by 

 Lieutenant J. M. Gillis ; with many others obtained through the kind- 

 ness of friends, that were kept at the various places visited by the Ex- 

 pedition, some made by authority, and others by individuals deeply 

 interested in this branch of science, have been incorporated on the 

 diagrams, thus enabling me to make a comparison with the daily 

 results of the Expedition at many places of great interest, particu- 

 larly those on our western or Pacific coast, and others on the eastern, 

 situated in nearly corresponding parallels of latitude. 



The duty of keeping the Meteorological Journals on board ship was 

 assigned to the medical officers of the Expedition ; those kept at the 

 observatories were superintended by the officers who were from time 

 to time engaged in astronomical duties. In some places omissions 

 will be observed : these have occurred from the unavoidable absence 

 of the officers on other duties, or from accidents to instruments, which 

 could not for a time be replaced. 



The meteorological instruments used by the Expedition were pro- 

 cured in 1836, from the best makers in England, France, and Ger- 

 many; others were prepared by Fisher, of Philadelphia, with great 

 care and accuracy. They were all compared with the standard, with 

 which they agreed. It was deemed essential at the beginning of the 

 cruise, to insure a uniform mode of observation by all the officers ; 

 the method of procedure was pointed out to all who were to be 

 engaged in the duty, and, it is confidently believed, was adhered to 

 throughout. Books of formulae were prepared for recording the obser- 

 vations. 



The diagrams scarcely need explanation ; they are of two kinds : 

 those giving the results at the observatory stations will be familiar to 

 all; the others, exhibiting the phenomena on the passages, are con- 

 structed on maps of Mercator's projection, showing the track of the 

 ships for each day ; lines drawn perpendicular, passing through the 

 figures on the track, will intersect the horizontal lines of temperature, 

 the scale of which will be found on the right or left hand column. 



