[ 237 ] 94 



now of Charleston, S. C. ; Doctors Milton Antony, Diisrard, and Ford, 

 of the Medical College in Augusta, Georgia; Dr. Henry Hull and- Mr. J. 

 Jackson, both professors in the university of Athens. Georgia; Mr. Fred- 

 erick Dugar, of Georgia ; Lieut. G. W. Long, Mr. J. Lewis, Col. A. Ma- 

 rat, and my friend L. Goldsborough, U. S. N., in Florida ; my friend, the 

 Rev. J. Lerne, and Mr. Girard, Mobile ; the Rev. Mr. Tissot, in New 

 Orleans ; Professor J. Lee Bliss, in Natchez ; Mr. J. Hamilton and Dr. 

 G. Troost, both professors in the university at Nashville; Captain J. Saun- 

 ders, U. S. engineers, at Pittsburg; Capt. R. K. Lee and Lieut. Bliss, U. S. 

 engineers, during their engineering operations at the Des Moines rapids, 

 on the Mississippi ; Mr. Henry H. Sibley and Major L. 'Taliaferro, at St. 

 Peter's : the Revs. P. J. Smedt and Felix "Werreydf, missionaries among 

 the Pottawatomies at Gamp Kearney, near Council Bluffs, on the Missouri ;. 

 the late Rev. J, A. Vansewecvelt, professor of niathemaiics and natural ()hi- 

 losophy in the university of St. Louis; last, my friend R. Paul, C. E , and 

 Dr. G. Englemann, at St, Louis. The most of these gentlemen supplied 

 me with months, and some with years, of meteorological observations, which 

 are of the utmost importance to me ; and the interest which they have 

 taken in my labors, from the commencement, has often excited me to per- 

 severance, under circumstances at times very little encouraging. But, to 

 my highly esteemed friend, Dr. Englemann, my special acknowedgment is 

 due for the great attention which he gave to the meteorological observa- 

 tions, for a period of more than three years. 



Dr. Englemann is not only a gentleman eminent in his profession, but 

 lie cultivates, also, with great distinction, several branches of natural liis- 

 tory ; and it is gratifying to the scientific traveller, going to the west, to 

 meet with a learned man such as Dr. Englemann ; — always warmly dis- 

 posed to assist him, and supply valuable information upon the country he 

 is visiting. 



The problem of the determinaii^m of altitudes above the ocean, is one 

 of the most interesting subjects for investigation that present themselves 

 in the vast field where pure mathematics are applied to physical phenomena. 

 All know that the height of mercury in a barometer depends upon the 

 weight of the air; and that this height lessens, the higher the observer is 

 in the atmosphere. Of this simple relation between the barometric heights 

 and the vertical space pas.^^ed through, men of science have taken advan- 

 tage, and have furnished formulae and tables, by means of which ihe prob- 

 lem can be more or less exactly solved. 



Among these methods, there is one which recommends itself, particu- 

 larly in practice, as procuring the greatest exactitude, and as being uni- 

 versal for all latitudes, and for all elevations above the sea ; — I mean that 

 of the illustrious author of the " Mecanique Celeste." I'he simple and 

 convenient tables of Mr. Oltmann, which were constructed in accordance 

 with this celebrated theorj^, are what I have used, throughout, m my cal- 

 culations.* 



There are two practical methods with the barometer for determining 

 the altitude of a place above the sea. The first consists in ascertaining 



* No bins; is wanting here, but ihe rigorous development of whal is observed to be practically 

 of some influence, but which has not jei been discussed in a manner conformable to the other 

 portions of the theory, — I mean the varying pressure of the vapor alwa)'s in the atmo^iphere, 

 according to its quantity and the temperature. But this does not require to be enlarged oa 

 now. 



