106 PROF. T. H. CORE ON THE MAGNETIC DIP, 



XVI. — Results of the Monthly Observations of the Mag- 

 netic Dip, Horizontal Force, and Declination, made at 

 the Magnetic Observatory of the Owens College, from 

 January 1874 to December 1876, inclusive. By Pro- 

 fessor Thomas H. Core, M.A. Comniunicated by 

 Professor Balfour Stewart, LL.D, F.R.S. 



Read January 23rd, 1877. 



This paper, containing the results of three years* magnetic 

 observations, is in continuation of a paper by Professor B. 

 Stewart, in No. 10, vol. xiii. of the Society's 'Proceedings,' 

 p. Ill, containing the results for 1873 of the Observations 

 for Dip and Horizontal Force. For convenience of refer- 

 ence. Dr. Stewart's numbers are incorporated in Tables I. 

 and II. 



The observations were made by Mr. Kingdon and myself 

 and latterly by Mr. Poynting; and the two days of the month 

 on which they were made were always as near the end of 

 the third week or beginning of the fourth week as possible. 

 The instruments and methods of observation were the same 

 as before. For the declination, which was not before ob- 

 served, in addition to the unifdar by Elliott Brothers, a 

 transit-theodolite by Troughton & Simms was used to de- 

 termine the azimuth of a fixed southern mark — the highest 

 point of the steeple of Heaton-Mersey church. A mean 

 of several transit-observations of the sun gave the south 

 azimuth of the steeple 14° o' 25". 



