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Astronomical Dialogues.

Pray explain this by an Instance, said she.

I Shewed you just now, said I, that the Latitude of London is found by the Help of this Meridian to be 51° 1/2; raise therefore the North Pole so, that the Northern Edge of the Horizon cut 51° 30′ of this Brass Meridian, reckoning from the Pole, and then London will be in the Zenith Point of the Globe.

I See it is, said the Lady, and I believe I see also the Reason why it must be so; for it is just as far (viz. 90°) from the Equator to the Pole, as from the Zenith to the Horizon; so that taking away the middle Part, which is common to both, the Latitude of any Place, and the Height of the Pole above its Horizon are all one in Quantity; and so I suppose 'tis called the Height of the Pole, because the Pole Star, which is near the Polar Point (as I think you told me) will appear, in the Night, just so high above the Horizon of any Place, as is that Place's Latitude.

Excellently Explain'd, Madam, said I, and yet I fancy you want to be told further, that the Height, or Altitude ofthe