62 Royal Society. 



of analysis itself, as the specimens of what, in the hands of 

 Dr. Prout, it has already performed: and not doubting, but 

 that by the exertion of such talents, such ingenuity, and such 

 labour, their satisfaction will from year to year be continually 

 increased. 



On delivering the Copley Medal to Lieutenant Henry Foster. 



Of all the accidental discoveries ever made by man, the 

 most unexpected and extraordinary, as well as most useful 

 in its consequences, appears to have been the magnetic needle. 

 No one could have thought it within the range of possibi- 

 lity to devise any plan, by means of which a ship in the midst 

 of a wide ocean, surrounded with perfect darkness, and tossed 

 by the winds and by the waves, might yet be able to ascertain 

 its course with the same certainty as in open day, and under 

 circumstances the most favourable. Yet the simple experi- 

 ment of a child floating a magnetized needle on a cork, directly 

 led to this important discovery. The variation must, without 

 doubt, have been immediately observed. Columbus is said 

 to have first noticed, and with astonishment and dismay, that 

 the variation increased as he proceeded on his great voyage of 

 discovery towards the West. Magnetism, a subject at once 

 so curious and so useful, was attended to with such care, that 

 the secular change of variation in the same place did not long 

 escape notice. The dip was early known ; and more than a 

 century ago observations were made on the daily change of 

 direction, and on a supposed relation which it bore to the ap- 

 pearance of northern lights, and to other natural phaenomena. 

 Nor were theories wanting : — some utterly gratuitous, as that 

 conjectured by the celebrated Dr. Halley, who supposed arbi- 

 trary points of attraction, and an internal earth or revolving 

 nucleus. Other theories, although given by less eminent men, 

 appear to be more conformable to trie true principles of gene- 

 ralizing by induction; as that quoted by Mr. Foster, from 

 Derham in his Physico-theology. But the accuracy of modern 

 experiment was wanting. The method of counting vibrations 

 to ascertain intensity had not then occurred ; nor were instru- 

 ments, in all probability, to be procured that were accurately 

 made, or of much delicacy of motion. In recent times, and 

 by a member of this Society *, we have seen the local attraction 

 of ships compensated on the most scientific principles ; terres- 

 trial direction neutralized ; and the line of action, at least of 

 diurnal variation, ascertained. 



And we have seen phaenomena little less astonishing than 



* Mr. Barlow. 



the 



