This page has been validated.
28
MAGNETIC OBSERVATORY.
[Chap. II.
1840
and ready co-operation of the Board of respective Officers, consisting chiefly of Lieut.-Col. Trelawny of the Royal Artillery, and Captain Alexander of the Royal Engineers, to whom I am more especially desirous to express thus publicly my thanks for the prompt and effectual means they adopted to forward the service with which I was charged.
Here as invariably on all volcanic islands, it was found quite impossible to obtain correct measures of the magnetic elements, by reason of the large amount of the disturbing influence of the rock itself. So powerful indeed was it in this particular instance, that even at the distance at which our ships were anchored it produced such anomalies in the results of our observations for the deviation of dip, variation, and intensity, as to mask the ordinary effects of the ship's iron. The comparisons of our magnetic instruments were just as unsatisfactory, for no two places could be found, however near to or distant from each other, where accordant results could be obtained even with the Feb. 9.same instrument. The importance, therefore, of St. Helena as a magnetic station will be manifested more by the detection of the momentary, irregular, and secular changes than by absolute determinations; and for meteorological purposes it cannot fail to be of essential advantage. Taking leave of our kind friend the governor, Col. Trelawney, Capt. Blackwell, and the officers of the 91st regiment, to whom we are all indebted for their attentions and
