256 



Reports on Special Researches 



Table 22 C. Results of Inclination Comparisons at Rome (Terracina), 1911 and 1913. 



Inclination obtained' 



C.I.W. 



+56 42.4 

 44.0 



Rome 



+56 43.6 

 45.0 



Mean value of (C. I. W. Rome 1911, needles 1 and 2). 



II 



Mean value of (C. I. W. Rome 1913, needles 1 and 2). . . 

 Mean value of (C. I. W. Rome 1913, needles 5 and 6). . . 

 Mean value of (C. 1. W.-Rome 1913, needles 15 and 16). 



+56 44.2 

 44.0 

 45.0 

 44.8 

 43.6 

 43.5 



C.I.W. - 

 Rome 



-1.2 

 -1.0 



-1.1 



-o.s 

 -1.1 



-2.4 

 -2.2 

 -0.9 

 -0.7 



-0.8 

 -1.0 



-2.3 



Remarks 



C. I. W. at B; Rome at A. 

 C. I. W. at A; Rome at B. 



C. I. W. at A: Rome at B. 



C. I. W. at B; Rome at A. 



'All results are referred to A: A = B 0'.3. 



Referring the mean results to I. M. S. (see p. 273), we obtain: 



(22) 1. M. S.-Rome (Dover magnetometer No. 122)= +0'.l (191 1-13). 

 (22a) I. M. S.-Rome (Dover magnetometer No. 122)= +0.00028// (191 1 

 (22i) I. M. S.-Rome (Dover dip circle No. 51, needles 1,2)= -0'.4 (191 1 



No. 23.-SAMOA OBSERVATORY. AT APIA. UPOLO. 



13). 

 -13). 



The comparisons at the Samoa Geophysical Observatory were made in May 1906 by 

 the Galilee party, using the regular observing-pier in the old absolute house. The instru- 

 ments used by the Galilee observers were C. & G. S. magnetometer No. 36 and Dover dip 

 circle No. 171. Some dip observations were also made for the Department of Terrestrial 

 Magnetism by Mr. G. Heimbrod in December 1906, he Ukewise using Dover dip circle 

 No. 171. The absolute instruments of the Observatory were in 1906: for decHnation and 

 horizontal intensity, Tesdorpf magnetometer No. 1975, the constants of wliich were 

 obtained by repeated comparisons with the Potsdam Observatory before and after 1906, so 

 that the observations with No. 1975 may be regarded practically as referred to the Potsdam 

 standard; for inclination, a Schulze earth inductor was used. Subsequent to 1906 or 1907, 

 Tesdorpf magnetometer No. 2025 was the Observatory absolute instrument, and was 

 referred to Potsdam by repeated comparisons of No. 2025 with No. 1975. In the pubUca- 

 tion' of Observatory results, 1905-1908, No. 2025 is called "Stations-theodolith," and No. 

 1975, "Anschluss-theodolith." Doctors Linke and Angenheister state^ that No. 2025 gives 

 too high east declinations by about 1', and that the Schulze earth inductor showed no 

 difference on the Potsdam standard ; it is furthermore stated that the pubhshed declinations 

 were all referred finally to Tesdorpf magnetometer No. 2025^ (presumably corrected in 

 accordance with the Potsdam comparisons). 



It appears that, in 1906, there was, for magnetic inclination, at the point of observation, 

 some local disturbance, which, according to information received from Dr. Angenheister, 

 was such as to diminish numerically negative values of dip by about 3' to 4'; the Galilee 

 values obtained with Dover dip circle No. 171 have been corrected accordingly by 3'. 5, 

 it being assumed that the Observatory values were similarly corrected. Several other 

 stations were occupied within the Observatory inclosure during May 1906, but, unfortu- 



'Ergebnisse der Arbeiten des Samoa-Observatoriums der koniglichen Gesellschaft der Wissenschaften zu Gottingen. 

 v. Die erdmagnetischen Registrierungen der Jahre 1905 bis 1908; von F. Linke und G. Angenheister. 



^Terr. Mag., vol. 15, p. 170. 



'This instrument was courteously loaned by the Samoa Observatory for the field work by Mr. G. Heimbrod, temporarily 

 connected with the Department of Terrestrial Magnetism in 1900. 



