An essay on the first principles of natural philosophy. Wherein the use of natural means, or second causes, in the oeconomy of the material world, is demonstrated from reason, experiments of various kinds, and the testimony of antiquity : in four books illustrated with copper-plates / by the Reverend William Jones.

  • Jones, William, 1726-1800.
Date:
1762
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Licence: Public Domain Mark

Credit: An essay on the first principles of natural philosophy. Wherein the use of natural means, or second causes, in the oeconomy of the material world, is demonstrated from reason, experiments of various kinds, and the testimony of antiquity : in four books illustrated with copper-plates / by the Reverend William Jones. Source: Wellcome Collection.

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    with this paflage, being himfelf ignorant of the telefcope, takes this dioptrum for the fights of a quadrant, or fome other geometrical inftrument. But how can thefe fights (unlefs they are telefcopic ones) afford any refemblance to that prophetical fagacity in the mind, whereby it fees things as yet at a diftance; to which nothing in the world can be fo nearly like, as that power of feeing diftant objeds by the help of optical glafies. As to plain fights of a quadrant &c. the eye is fo far from being aflifted by them when it views a diftant objed, that the chief difficulty an artift has to contend with, is that of making the accuracy of the line of collimation upon the inftrument confift with clear and diftind vifion. IT may feem ftrange indeed, that if dioptric glajfes were anciently in ufe, we ffiould hear of them no oftener in the writings of the ancients. This may be hard to account for; and yet it may be very unfafe to draw a pofitive conclufion from negative evidence. Friar Bacon mentions the refrac¬ tions of the fun’s rays through a glafs fphere: but as he docs not fay totidem verbis that he ever viewed an objed through fuch a Iphere, the* learned Dr. Smith is of opinion (if I do not mifunderftand him)'that he had no experience of its magnifying power. See Opticks, Vol. II. p. 21. R. And had Seneca defcribed his glafs ball filled with water only as a burning glafs, this might have tempted us to ar¬ gue, that he knew nothing of its ufe in magnifying letters : only he happens to have precluded fuch a conjedure by de¬ claring the contrary. He might know more than he has (poken of: the mathematicians and workers in glafs of thofe days might know more than he did : and the ancient Greeks and Phoenician might know more than the Latins: but the accounts