The Publisher to the Reader.

as his intention was to do (which is evident from several passages in his writings), yet the learned will here meet with several matters explained that are no less difficult than curious. Among the rest is that great problem of memory, which is here at least intelligibly explained, along with the organs necessary to perform that action of the mind, or reflection, which organs possibly are not immaterial or incorporeal.

From this contemplation he comes to treat of time and duration, showing whence we gain the notion of it, which he supposes comes from the formation of and impressions upon sensible and corporeal ideas, or images stored up in the repository of the brain, though he positively asserts the recipient and directing power, or soul, to be a self-moving immaterial being.

Next to this is a physical treatise of comets, proving from many observations that they are actually burning bodies, with an account of the inconceivable velocity of the motion of the flashes or ignition of the steams in the blaze or tail, far surpassing those of lightning. To this is joined the author's hypothesis of the cause of gravity, a subject that has hitherto puzzled as well as exercised the most ingenious heads. This hypothesis is deduced from mechanical principles and backed with experiments; to which is added a short account of his hypothesis of magnetism.

After these are many lectures concerning the external shell or surface of the Earth, the cause and origin of mountains, valleys, and lakes, and of fossil shells and other marine remains found on the highest hills over most part of the known world, with historical accounts of earthquakes, fiery eruptions, deluges, etc., and a physical interpretation of the most ancient mythological representations of natural history. In these lectures, the figure of the terraqueous globe and the encompassing air is proved from the diurnal motion and gravitation.

Lastly, I have added some lectures relating to the improvement of astronomy and navigation, wherein, though I cannot promise the reader the invention of the longitude or the like great matters, yet I hope they will prove agreeable for the several new and useful suggestions and instruments mentioned and described therein, with some new methods of making observations on land and sea to determine the true meridian, latitude of the place, etc.

In all these discourses I have fairly and truly given the author's own opinions and reasonings in his own words, with the several times when they were read before the ROYAL SOCIETY, when I could any way discover them.

I could wish the author had himself fitted these papers for the press in his lifetime, or at least stitched the several agreeing subjects together, which would have prevented some errors that have possibly happened in the order and disposition of them. For this, I desire the reader to accept this excuse: that several of his papers came to my sight and hands when others that might better have followed them were already printed off.