204 REPORT ON 



The observed values of log. m show no trace whatever of any change depending 

 upon the time, and therefore the indiscriminate mean of them all has been taken 

 as the truth, and we have 



Log. m 9.8211 0.0016. 

 The probable error of a single observed value of log. m is i 0.0058. 



The following table contains all the observations which were made at the position 

 occupied by the Admiralty Standard Compass on board the Monadnoek, for the 

 determination of absolute force. The first nine columns contain quantities precisely 

 similar to those in the columns headed in the same manner in the table last given. 

 The column headed "Log. //'" gives the logarithm of the combined horizontal 



force of the earth and ship, obtained by subtracting log. - ' from the value of log. 



H 



m given above. The column "0"' contains the dip, Avhich was observed immedi- 

 ately after the deflections. The column "Log. Z'" contains the logarithm of the 

 combined vertical force of the earth and ship, computed from the quantities in the 



TTI 



tenth and eleventh columns by the formula Z' = H' tan 0' . The columns " Log. ," 



yi H 



and "Log. "^ explain themselves when it is stated that // represents the hori- 

 zontal force of the earth ; H' the combined horizontal force of the earth and ship ; 

 Z the earth's vertical force; and Z' the combined vertical force of the earth and 

 ship. The column "'" contains the azimuth of the ship's head as read off from 

 the compass card at the time the deflections were observed; and the column "" 

 contains the same azimuth, counted from the true magnetic north. 



