PART II.— ASTRONOMY. 



Astronomical Observations and Calculations made in 1823, 

 during the Expedition to the Source of St. Peter^s River, 

 Sfc. by J. Edward Colhoun, Astronomer, Sfc. to the Ex- 

 jtedition. 



The instruments used in making the following astronomical 

 observations, were, 



A brass sextant, of five inches radius, divided by means of 

 a vernier to 30", made by Cary, London. 



A common surveyor's compass, marked to degrees, and 

 having a needle four inches long. 



An artificial horizon of mercury. 



A patent lever watch, by Robert Roskell, Liverpool. 



Except in two or three instances, when the rate of the watch 

 was found, altitudes were taken for time, a few minutes, 

 either before or after the lunar distances were measured. 



In giving the data, the error of the watch is indicated as 

 exceeding or being less than apparent time, by having no alge- 

 braic sign or the sign — prefixed ; the index error continues the 

 same, till otherwise stated; the object to the east is mentioned 

 first; in general, it is the mean of three times, three altitudes 

 or three distances, which is recorded. 



Many observations, embracing every kind of which the sex- 

 tant is capable, are not inserted, because taken at points that 

 cannot be easily designated. They have answered a sufficient 

 purpose in corroborating those here given, and in correcting 

 estimated courses and distances. 



It was endeavoured by frequency and variety of obsei-vation, 

 to supply the want of better instruments. If this deficiency 



