v j 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 tin- expense that would have 

 been incurred. 



The Meteorological Registers that were kept in connexion with tin 

 Kxp -.lit ion at Cambridge, Mass., by Win. Cranch Bond, Esq., Astro- 

 nomer. Harvard College, and at the naval dep&t, Washington City, by 

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

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

 pedition, M>me 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 dutv of keeping the Meteorological Journals on Ixmrd ship w r as 

 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 lie 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 pr<>- 

 ciired in 1836, from the In-st makers in England. France, and (Jer- 

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

 and accuracy. Thev were all compared with the standard, with 

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

 cruise, to in-nre a uniform mode of observation by all the officers : 

 the method of procedure was [minted out to all who were to be 

 engaged in the dutv. and. it is confidently Itelieved. was adhered to 

 throughout. Hooks of form n hi- were prepared for recording the obser- 

 vation-. 



The diagram,- scarcely need explanation ; they are of two kinds : 

 those giving the re.-ults at the observatory stations will l>e familiar to 

 all; the others, exhibiting tin- phenomena on the pas.-age<. are eon- 

 .ted mi maps of Meiv,,t'.i'.- projection, showing the track of the 

 nhi| '.it-li day: line- drawn per]>eiidicular. pa ing through the 



figure- on the trsick. will intersect the hori/.ontal lines of temperature, 

 the x-ale of which will lc found on the right or left hand column. 



