10 



PERCY SLADEN TRUST EXPEDITION 



The accompanying chart shows the positions, both afloat and ashore, at which 

 observations were made ; and the amount of magnetic variation found at each. There 

 are scarcely sufficient observations from which to protract the curves of the magnetic 

 elements which were observed on shore only; but those of equal declination, deduced 

 from the results obtained both at the fixed and floating positions, are shown ; and 

 are of interest, pointing as they do, to the fact of considerable divergence from the 

 parallelism usually seen in general charts of these curves ; — due, of course, to in- 

 sufficiency of data. 



Fig. 1. Chart showing curves of Equal Magnetic Variation (Declination). 



There seems little doubt that, as information increases, so will the complexity 

 of the lines of equal variation. 



The rapid change in variation in the area north of Madagascar is very notice- 

 able, and of great importance to the navigator. It will be seen that there is a 



