It is one of the melancholy pleasures of an old man, to recollect the kindness of friends, whose kindness he shall experience no more.  I have now none left to favour my studies; and, therefore, naturally turn my thoughts on those by whom I was favoured in better days:  and I hope the vanity of age may be forgiven, when I declare that I can boast among my friends, almost every name of my time that is now remembered:  and that, in that great period of mathematical competition, scarce any man failed to appear as my defender, who did not appear as my antagonist.

By these friends I was encouraged to exhibit to the Royal Society, an ocular proof of the reasonableness of my theory by a sphere of iron, on which a small compass moved in various directions, exhibiting no imperfect system of magnetical attraction.  The experiment was shown by Mr. Hawkesbee, and the explanation, with which it was accompanied, was read by Dr. Mortimer.  I received the thanks of the society; and was solicited to reposit my theory, properly sealed and attested, among their archives, for the information of posterity.  I am informed, that this whole transaction is recorded in their minutes.

After this I withdrew from publick notice, and applied myself wholly to the continuation of my experiments, the confirmation of my system, and the completion of my tables, with no other companion than Mr. Gray, who shared all my studies and amusements, and used to repay my communications of magnetism, with his discoveries in electricity.  Thus I proceeded with incessant diligence; and, perhaps, in the zeal of inquiry, did not sufficiently reflect on the silent encroachments of time, or remember, that no man is in more danger of doing little, than he who flatters himself with abilities to do all.  When I was forced out of my retirement, I came loaded with the infirmities of age, to struggle with the difficulties of a narrow fortune; cut off by the blindness of my daughter from the only assistance which I ever had; deprived by time of my patron and friends; a kind of stranger in a new world, where curiosity is now diverted to other objects, and where, having no means of ingratiating my labours, I stand the single votary of an obsolete science, the scoff of puny pupils of puny philosophers.

In this state of dereliction and depression, I have bequeathed to posterity the following table; which, if time shall verify my conjectures, will show that the variation was once known; and that mankind had once within their reach an easy method of discovering the longitude.

I will not, however, engage to maintain, that all my numbers are theoretically and minutely exact:  I have not endeavoured at such degrees of accuracy as only distract inquiry without benefiting practice.  The quantity of the variation has been settled partly by instruments, and partly by computation:  instruments must always partake of the imperfection of the eyes and hands of those that make, and of those that use them:  and computation, till it has been rectified by experiment, is always in danger of some omission in the premises, or some errour in the deduction.