258 Reports on Special Researches 



The inclination results just given, on account of the local disturbance stated above, 

 are not of sufficient accuracy to serve more than as a control on the corrections of dip 

 circle No. 171. 



The declination results, as well as those from the horizontal intensity comparisons, 

 because of their meagerness, are to be regarded only as approximate quantities; if they 

 are referred to I. M. S. (see p. 273), we obtain: 



(23) I. M. S.- Samoa (Tesdorpf magnetometer No. 1975)= +1' (1906). 

 (23a) I. M. S.- Samoa (Tesdorpf magnetometer No. 1975)= +0.0003// (1906). 



Attention must again be called to the fact that Tesdorpf magnetometer No. 1975 was 

 replaced after 1906 by Tesdorpf magnetometer No. 2025. 



No. 24.-TASHKENT OBSERVATORY, ASIATIC RUSSIA. 



Comparisons were made at the Tashkent Observatory by Observer J. C. Pearson, in 

 the course of his field work, September 3-6, 1909, but the Observatory data have not yet 

 been received. 



No. 25.-TIFLIS OBSERVATORY. KARSANI. EUROPEAN RUSSIA. 



Comparisons were obtained at the Tiflis Observatory by Observer J. C. Pearson in 

 June 1908 and again in June-July 1909, before and after extensive field work. In 1905 

 this Observatory, on account of disturbance from electric car lines, was removed from Tiflis 

 to Karsani, in the mountains, near the village of Mtskhet, on the Batum-Tiflis railway and 

 about 20 kilometers north of Tiflis. 



In 1908 the comparisons were made as follows: On June 8 simultaneous sets of declina- 

 tion, inclination, and horizontal intensity were obtained, Mr. Rosenthal, of the Observatory, 

 observing in the alssolute house (A) and Air. Pearson on a wooden pier (P) distant about 

 350 yards (320 meters) east of and below the absolute house. Mr. Pearson placed the 

 tripod of his instrument centrally over P and mounted his magnetometer (C. I. W. No. 5) 

 on this tri])od. The two observers could not exchange stations owing to the non-portability 

 of the Observatory instruments, wliich consisted of a Wild-Edelmann theodolite magnetom- 

 eter and earth inductor. The existence of a slight local disturbance in this region produced, 

 according to information supplied by Director Hlasek, the following station-differences: 

 for declination, A P= +0'9, and for inclination, A P= l!7. For horizontal inten- 

 sity, the station-difference had not been definitely determined at the time; for the single 

 observation here involved, namelj^ on June 8, it was assumed zero. 



Accordingly Air. Pearson made his subsequent observations in the absolute house. 

 This house contains two stone piers about 30 inches (76 cm.) apart; on the southern one 

 {As) is placed the Wild-Edelmann magnetometer (for declination and deflection observa- 

 tions), and on the northern one (An) the magnet house (with suspension tube) is mounted 

 for oscillation observations. Air. Pearson was obliged to use the latter pier (A) and it 

 had to be assumed that the station-difference between the two piers, An and ^5, is 

 zero. The Observatory results for declination apply strictly to pier As, whereas those for 

 horizontal intensity refer to a mean position of A^ and A,i. While Air. Pearson occupied 

 A, the magnet house with suspension tube of the Observatory magnetometer was removed. 



The Observatory mark could not be used by Air. Pearson in the declination work at 

 the pier A, and, accordingly, he was obliged to use a new mark, the azimuth of which was 

 determined by him as follows : 



1. June 9, 10, 1908, from Polaris observations 229 26'.5 W. of S. 



2. July 2, 3, 1909, from Sun observations 26.0 



.3. July 1909 t\y transfer from Observatory mark and azimuth 26.0 



Adopted 229 26'.2 



