•APPENDIX. 



METEOROLOGY, & c. 



By Mr. J. W. Seaman. 



Quartermaster's Depot, Fort D. A. Etjsseljl, 



November 1, 1870. 



Sir: I have the lienor herewith to present the meteorological notes 

 taken during the month of July, August, September, and October, 

 while connected with the geological survey of Wyoming Territory under 

 your charge. These notes have been taken in connection with other 

 duties, not in a professional, but rather in an amateur way. This will, I 

 trust, account for many apparent imperfections and omissions. The instru- 

 ments placed at my disposal were an aneroid barometer with accompany- 

 ing Fahrenheit thermometer; a Fahrenheit thermometer manufactured 

 by C. A. Siefert, Boston, Massachusetts ; two Fahrenheit thermometers 

 manufactured by J. Kendall & Co., New Lebanon, New York ; also, one 

 odometer for the measurement of the road. There has been a barometric 

 observation taken at every camp and many points of importance on the 

 survey. As will be seen by an inspection of the table^, the observed 

 readings at the same place often vary several tenths of an inch. This 

 is owing to a change in density of the atmosphere each hour, and with 

 every wind and rain ; hence the heights are but approximately indicated. 

 There has been no allowance made for a change iu temperature, as it is 

 but slight. There has been no allowance made for the wind, as I have 

 had no means of determining its force. I have made no allowance for 

 moisture, as I have had no hygrometer. The rule which has been fol- 

 lowed in making the estimates of elevation is one given by J. H. Bell- 

 ville, of the Boyal Observatory, Greenwich. Hide. — " As the sum of the 

 readings of the barometer is to their difference, so is 55,000 (or twice the 

 assumed height of the atmosphere in feet) to the elevation required." 



This rule is founded on the supposition that the height of the atmos- 

 phere is 27,500 feet, with the barometer at 30 inches and the thermome- 

 ter at 55° Fahrenheit. The temperature has been noted at the time of 

 taking each reading ; so that if there could be a more accurate estimate 

 made by allowing for a change, it might be made. The aneroid is one 

 purchased in Philadelphia of McAllister & Bro., 728 Chestnut street. 

 The divided circle is only two inches in diameter. Its small size recom- 

 mends it to those desiring a very convenient portable instrument; but 

 on the other hand it is too small for the most accurate work. The tem- 

 perature during the time occupied in the held has ranged from 103°, 

 Quartermaster's Department, Fort D. A. Bussell, July 28, 2.30 o'clock 

 p. m., down to 8°, Big Pond Stage Station, Bitter Creek, 3.30 o'clock a. 

 m., October 17. We have experienced few storms of rain or snow. The 

 general direction of the wind has been from northwest or southwest. 

 On the evening of September 24, at Camp Elliott, there was a most gor- 



