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X. Results of Magnetic Observations at Stations on the Coasts of the British 



Isles, 1907. 



By Commander L. W. P. CHETWYND, R.N., Superintendent of Compasses. 



Communicated by Rear-Admiral A. M. FIELD, F.Ii.S. 



Received July 14, Read December 10, 1908. 



1. WITH a view to comparing the values of Secular Change of Declination, Horizontal 

 Force and Dip, at various stations on the coasts of the British Isles, with the values 

 derived from the continuous records at Kew Observatory, the Hydrographer (Rear- 

 Admiral A. MOSTYN FIELD, F.R.S.) directed that during the year 1907 observations 

 were to be made at certain stations, selected from those which had been occupied 

 by Prof. RtiCKER and Dr. THORPE during their Magnetic Survey* for the epoch 

 1st January, 1891. 



2. The observers detailed for the work were Captain M. H. SMYTH, R.N., 

 H.M.S. "Research"; Captain W. PUDSEY-DAWSOX, R.N., H.M.S. "Triton"; and 

 Captain J. W. COMBE, R.N., H.M. Surveying Vessel " Gladiator." 



(The observers' names are subsequently indicated by their initials.) 



The instruments with which they were supplied were : 



M. H. S 



W. P.-D 



J. W. C. 



3. Careful reference, kindly verified by Dr. THORPE, was made to ensure the exact 

 observation spot at each station being re-occupied. 



4. To reduce all results to a common instrumental standard, observations were 

 made at Kew, before the commencement of the field observations and after their 

 completion, and the results of comparing the values obtained by each instrument with 

 the values derived from the magnetograms were applied as corrections for instrumental 

 differences, thus reducing the field observations to the Kew Instrumental Standard. 



The corrections so applied are given in Table I. 



* 'Phil. Trans.,' A, vol. 188 (1896). 

 VOL. CCIX. A 450. 2 G 2 25.1.09 



