1877.] b4:d [Frazer. 



S. Harris and H. M. Noad, and "Diurnal Variations of Declination," by 

 Wm. Norton, have been consulted. 



A large number of observations with their authorities will be found at 

 the end of the Report of C. A. Schott in C. S. Report for 1858. 



Resume from Coast Survey Reports. 



In the C. S. Report for 1855, p. 302, is a chapter by Prof. A. D. Bache, 

 on the Magnetic Declination in the northern part of the Gulf of Mexico. The 

 observed declinations are reduced to the common date of Jan. 1850, by ain 

 assumed annual decrease of 0'.5 E. declination from observations made at 

 Pascagoula in 1847 and 1855. 



The equation representing the true declination with reference to the lati- 

 tude L and the longitude M of any place, here follows : 

 dV =r V + X dL + y dM + z dL dM + p dL^ + q dM^ 

 dV = difference between the observed decl. and the assumed decl. V 



V = correction to the assumed V. 



The solution of the conditional equation, for any latitude L and longi- 

 tude M gives the following expression for V : 



dL = L — 280.04. dM = M — 880.69. 

 V ^ 70.39 East— 0.025 dL + 0.296 dM-f 0.0188 dL dM— 0.0094 dL-— 

 0.0076 d M^ 



All the declinations being East are treated as essentially positive quanti- 

 ties. 



The number of groups of stations selected was six, in order to solve the 

 six unknown quantities in the first equation. 



There were the following number of stations in each group. The Ro- 

 man numeral indicates the number of the group, and the Arabic numeral 

 the number of stations : I, 1 ; IL 1 ; HI, 4; IV, 4 ; V, 3 ; VL 1- 



The average of the residual — (/. e. the diiference between the observed 

 and computed declinations) — was QO 056 = 3'. 3. 



For the observations in the general table, the form of the conditional 

 equation is the same as above. 



V = V' + v-fxX + yY + zXY + pX2 + qY^ 



The annual variations were an estimated approximation by mutual com- 

 parison of the known values at Toronto and on the Atlantic coast. 



The origin of co-ordinates is assumed midway between lat. 43° 26', long. 

 70° 24'; and lat. 290 07', long. 830 03'; the co-ordinates of position are ex- 

 pressed in degrees and decimals and icerc grapliically obtained by caretul 

 plotting on a large scale. 



Mr. Chas. A. Schott in the same volume furnishes a discussion of the 

 magnetic declination on the Atlantic and part of the Gulf coast (communi- 

 cation to the American Association for the Advancement of Science, Ap- 

 pendix 48 to Coast Survey Report for 1855,) of which the following are 

 some of the points : 



Hausteen's publication "Investigations of the secular variation since the 

 magnetic observations in Coast Survey Report of 1854," gave a new im- 

 pulse to these investigations. 



