Ouranoskopia, or, The contemplation of the heavens, in a perpetual speculum, or general prognostication for ever wherein is succinctly demonstrated the names and natures of the signs, planets and aspects, terms of art, order of the spheres, the colours, magnitudes, motions, solid proportions and distances of the seven planets from the earth ... / by Iames Corss ...

CHAP. XXVII. How to finde the Altitude of any Tower, Castle or Steeple, &c.

IF I should endeavour to instruct you by Precept and Example, in every various Scituation and Demonstra∣tion that might be proposed, for attaining the true heights of Towers, Castles, Steeples or Hills, &c. by the Quadrant, I should exceed my intention in this place, for it would require a peculiar Treatise by it self (which I may happily publish, if God continue my life) And therefore I shall (here in this Chapter) only shew you, how (by your Quadrant, with, and without Calculation) to know all heights accessible,

First, by Calculation.

Lift up your Quadrant towards the Tower or Steeple whose Altitude you require, untill you behold (through both the sights) the very Summity or Top; which found, mark well the Divisions or Points in your Square, which the Threed and Plummet did fall on: And if they be of right shaddow (that is to say when the Threed and Plummet falls on that side of the Square which is next the sights) Then say, As the Parts out, is to the whole Scale. So is the length of the Base, to the Altitude of the Tower: And therefore multiply the distance from you to the Base by 12. the product divide by the

parts cut (by the fall of the Plummet) the Quotient will show you the Altitude required. — But if the Threed fall upon the contrary shaddow, then say, As the whole Scale is to the parts cut, So is the length of the Base, to the Altitude required. And therefore multiply the Base by the parts cut, the product divide by the whole Scale, and the Quotient is your desired Al∣titude above the Level of your Eye.

Example, Suppose the Threed with the Plummet should happen to fall on 6 parts of contrary shaddow, and the distance from your standing to the Base of the Tower be 120 foot: I say,— As the whole Scale 12, is to the parts cut 6, So is the length of the Base 120 foot, to the Altitude of the Tower 60 foot. Thus mul∣tiplying the Base 120, by the parts cut 6, the product 720 divided by 12, the Quotient is just 60, and so many foot high is that Tower or Steeple above the Level of your Eye.

Secondly, Without Calculation.

Because there may be some Ingenious Men, that would know the Altitude of a place, and yet hath no Arithme∣tick to Multiply and Divide: therefore to satisfie such, I give this Direction. That if the Tower or Steeple, &c. be accessible, then hold your Quadrant up towards it, looking diligently through both the sights, going back∣ward or forward, untill the Line of the Plummet fall on 45 degrees. Which found, Measure the distance between your standing and the Base, for that is the just Altitude of the Tower, above the Level of your Eye, as you required.