PLATE XIX.
Is a Plan of the principal Stars that form the Pleiades, correctly taken by a Combination of Triangles, as in the Figure, from whence it will naturally follow, all the whole Form being comprehended in much less than one Degree. That the most minute local Motion in any one of those Stars in a very few Years, will be made sensible to an Eye at the Earth. For Instance, if any of the Stars that form the Letter A, or T, within the Term of ten or twenty Years, be found in the least to deviate from the Lines of their present Position and Direction, it will be evident beyond a Contradiction, that they have a Motion amongst themselves, and since at such a Distance they cannot possibly be affected by the Earth, it must be a Motion of their own; and thus if any one can be proved, to change its Situation, with regard to the rest, we can have no new Difficulty in concluding that they all may do the same.
Thus if any of the regular Triangles M B Z, Z P H, A Z M, Y A Γ, or Π Ο I, &c. in due Time be carefully noted, we may venture to say with great Safety, that the thousandth Part of a Degree will be plainly discovered.