PREFACE. V 



meter, graduated to 30' by the vernier, for trigonometrical 

 purposes. 



14th. Three mountain barometers, by M. Fisher and Son. 

 Two of them got entirely out of order in the course of our 

 travels. 



15th. Several mercurial thermometers, and one of alcohol. 

 By the same, graduated by Fahrenheit's scale. 



" 16th. Our collection of instruments also embraced several 

 of less note, viz. six travelling compasses, several pocket 

 compasses, a small pocket telescope by Doland, several mi- 

 croscopes, a measuring tape, &c. Sec." 



The astronomical and other calculations are divided into 

 two parts. Part first, contains the observations which were 

 made and calculated entirely by myself except in one or two 

 instances. I have entered the observations of my friend Lieu- 

 tenant A. Talcott of the corps of Engineers, made when we 

 were travelling'together, and have taken a mean between the 

 results obtained by him and mvself in those instances. Part 

 second contains the observations which were made by Major 

 Long and Lieutenant Swift after I separated from them at 

 Engineer Cantonment, and which were afterwards calculated 

 by me while those officers were engaged in projecting maps 

 of the country explored by the Expedition. 



All the latitudes in Part first, and all except three in Part 

 second, are deduced from the double meridian altitudes of 

 the sun or stars, (and in one other instance in Part second, 

 the double meridian altitude of the moon was observed,) to 

 which the index error of the instrument is applied, which was 

 always determined immediately preceding or after the obser- 

 vation, by measuring the diameter of the sun from each side 

 of 0, (zero,) on the limbs of the instrument, and taking half 

 the difference of the diameters thus measured, for the index 

 error, which was called + (plus,) and added when the ex- 

 cess was on the negative or right hand side of on the limb 

 of the instrument, otherwise the error was called — , (minus,) 

 and subtracted from the observed double altitude. In Part 

 first the refractions answering to the apparent altitudes of the 

 objects have alwavs been corrected for the state of the baro- 

 meter and thermometer, so that if any one should choose to 

 look them over, this correction must be found by reference to 

 the meteorological register, which will accompany this paper. 

 In 'Part second the refractions could not be corrected for the 

 state of the atmosphere, as there was no barometer to refer to. 

 All the observations in Part second for latitude, longitude by 



