Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/379

 sheweth his distrust of a Spherical Instrument composed by Archimedes hismelf to take the Suns ingression into the Æquinoctial.

But if the Instruments be so suspitious, and the observations so dubious, how can we ever come to any certainty of things, or free our selves from mistakes? I have heard strange things of the Instruments of Tycho made with extraordinary cost, and of his singular diligence in observations.

All this I grant you; but neither one nor other of these is sufficient to ascertain us in a businesse of this importance. I desire that we may make use of Instruments greater by far, and by far certainer than those of Tycho, made with a very small charge; the sides of which are of 4. 6. 20. 30. and 50. miles, so as that a degree is a mile broad, a minute prim. 50 * yards, a second but little lesse than a yard, and in short we may without a farthing expence procure them of what bignesse we please. I being in a Countrey Seat of mine near to Florence, did plainly observe the Suns arrival at, and departure from the Summer Solstice, whilst one Evening at the time of its going down it appeared upon the top of a Rock on the Mountains of Pietrapana, about 60. miles from thence, leaving discovered of it a small streak or filament towards the North, whose breadth was not the hundredth part of its Diameter; and the following Evening at the like setting, it shew'd such another part of it, but notably more small, a necessary argument, that it had begun to recede from the Tropick; and the regression of the Sun from the first to the second observation, doth not import doubtlesse a second minute in the East. The observation made afterwards with an exquisite Telescope, and that multiplyeth the Discus of the Sun more than a thousand times, would prove easie, and with all delightful. Now with such an Instrument as this, I would have observations to be made in the fixed stars, making use of some of those wherein the mutation ought to appear more conspicuous, such as are (as hath already been declared) the more remote from the Ecliptick, amongst which the Harp a very great star, and near to the Pole of the Ecliptick, would be very proper in Countries far North, proceeding according to the manner that I shall shew by and by, but in the use of another star; and I have already fancied to my self a place very well adapted for such an observation. The place is an open Plane, upon which towards the North there riseth a very eminent Mountain, in the apex or top whereof is built a little Chappel, situate East and West, so as that the ridg of its Roof may intersect at right angles, the meridian of some building standing in the Plane. I will place a beam parallel to the said ridg, or top of the Roof,