of comets began then to be very much in vogue.  The celebrated Bernoulli concluded by his system that the famous comet of 1680 would appear again the 17th of May, 1719.  Not a single astronomer in Europe went to bed that night.  However, they needed not to have broke their rest, for the famous comet never appeared.  There is at least more cunning, if not more certainty, in fixing its return to so remote a distance as five hundred and seventy-five years.  As to Mr. Whiston, he affirmed very seriously that in the time of the Deluge a comet overflowed the terrestrial globe.  And he was so unreasonable as to wonder that people laughed at him for making such an assertion.  The ancients were almost in the same way of thinking with Mr. Whiston, and fancied that comets were always the forerunners of some great calamity which was to befall mankind.  Sir Isaac Newton, on the contrary, suspected that they are very beneficent, and that vapours exhale from them merely to nourish and vivify the planets, which imbibe in their course the several particles the sun has detached from the comets, an opinion which, at least, is more probable than the former.  But this is not all.  If this power of gravitation or attraction acts on all the celestial globes, it acts undoubtedly on the several parts of these globes.  For in case bodies attract one another in proportion to the quantity of matter contained in them, it can only be in proportion to the quantity of their parts; and if this power is found in the whole, it is undoubtedly in the half; in the quarters in the eighth part, and so on in infinitum.

This is attraction, the great spring by which all Nature is moved.  Sir Isaac Newton, after having demonstrated the existence of this principle, plainly foresaw that its very name would offend; and, therefore, this philosopher, in more places than one of his books, gives the reader some caution about it.  He bids him beware of confounding this name with what the ancients called occult qualities, but to be satisfied with knowing that there is in all bodies a central force, which acts to the utmost limits of the universe, according to the invariable laws of mechanics.

It is surprising, after the solemn protestations Sir Isaac made, that such eminent men as Mr. Sorin and Mr. de Fontenelle should have imputed to this great philosopher the verbal and chimerical way of reasoning of the Aristotelians; Mr. Sorin in the Memoirs of the Academy of 1709, and Mr. de Fontenelle in the very eulogium of Sir Isaac Newton.

Most of the French (the learned and others) have repeated this reproach.  These are for ever crying out, “Why did he not employ the word impulsion, which is so well understood, rather than that of attraction, which is unintelligible?”

Sir Isaac might have answered these critics thus:—­“First, you have as imperfect an idea of the word impulsion as of that of attraction; and in case you cannot conceive how one body tends towards the centre of another body, neither can you conceive by what power one body can impel another.