Academia scientiarum, or, The academy of sciences being a short and easie introduction to the knowledge of the liberal arts and sciences, with the names of those famous authors that have written on every particular science : in English and Latine / by D. Abercromby ...

Sect. XXIV. Perspective.

PErspective representeth every object seen in some Diaphane, or trans∣parent Medium, through which the vi∣sual Rays are terminated or bounded on the object; and generally what▪ is seen through something, as through the Air, Water, Clouds, Glass, and the like, may be said to be seen in Perspective.

The chief Contents of this Science, may be referred to these following Heads.

The Ray is a streight line drawn from the Eye to the Glass perpendicularly.

That point is called Primary, on which falls a perpendicular line drawn from the Eye to the Glass.

The projection of a line, is not a crooked line.

The object being a Point, there is but

one visual Ray drawn from the Object to the center of the Eye, and this Ray is called the Axis, or Centrical, as being the most vivid, and the strongest of all.

If the Object be a streight line, the visual Rays make a triangle. If the Ob∣ject be a Surface, plane or spherical, the visual Rays represent a Pyramide.

Ichonography is the Pourtraiture of the Platform or Plane upon which we would raise any thing.

Orthography is the Pourtraiture of the fore part of the Object.

Scenography representeth the Object wholly elevated and perfect, with all its Dimensions and Umbrages on all sides.

The Horizontal line in Perspective, is taken from the height of our eye: This is the chief piece of the Picture, and which ought to be the rule of the di∣mensions and height of the Figure.

The point of Perspective, or sight, is made by the centrical Ray above the Horizon.

Authors.

Amongst the chief Writers of Per∣spective, you have Roger Bacon, John Baptist Porta, Stevin, Marole, John Cousin, Daniel Barbaro, Vignola, Serlio, du Cereau, Salomon de Caus, Guidus Ubaldus, Niceronius, &c.