1893.] Magnetic Observations in Senegambia. 361 



traced for many of the lines present in their photographs, 

 which do not appear in the Kensington photographs, and some 

 of these may. therefore, be really due to iron, their absence 

 from, the Kensington photographs being due to insufficient 

 exposure, or to the employment of different temperatures. The 

 almost constant difference of O'l tenth-metre between the two 

 sets of measures is a satisfactory indication of the accuracy of 

 both. 



4. The impurities which contribute the greater number of foreign 

 lines to the spectrum of the electrolytic iron employed by the 

 author are Ca and Mn, though there is decided evidence of 

 the presence in minute quantities of various other elements. 



This research on the arc spectrum of iron is made in connection 

 with a wider investigation on the arc spectra of the other metallic 

 elements, the results of which will be communicated to the Society in 

 due course. 



II. " Magnetic Observations in Senegambia." By T. E. THORPE, 

 F.R.S., and P. L. GRAY, B.Sc., Assoc. R.C.S. Received 

 October 31, 1893. 



On the occasion of the recent Eclipse Expedition to Senegambia 

 we took with us a set of magnetic instruments of the Kew pattern, 

 with a view of making observations in a district for which the mag- 

 netic elements have not hitherto been determined. The instruments 

 employed were magnetometer No. 61, by Elliott Brothers, dip circle 

 No. 94, by Dover, and chronometer Dent 1932. They were part of the 

 equipment made use of in connexion with the Magnetic Survey of 

 the British Isles. 



Observations were made at Fundium, Senegal, and at Bathurst, on 

 the River Gambia. 



The results are as follows : 



Fundium, Senegal, lat. 14 7''4 K, long. 16 32' W. (appro*.). 



The observations were made in the vicinity of the Eclipse Camp, 

 and on a partially enclosed piece of ground between the Admini- 

 strator's house and the River Salum, about 80 yards from the shore. 

 The temperature during the force observations was about 30 C. 



