On luminous rays and the power of their extremes
Light rays as pyramids: two equal rays meeting are doubled in power
This folio opens a study 'on luminous rays and the powers of their extremes.' A series of diagrams — a horizontal line, two eyes observing a line, and pairs of crossed lines — is annotated with numbers (1 2 1, 1 2 4, 1 1 - 2, 1 4). The accompanying text argues that a light ray is of 'pyramidal' power, so that when two rays from equal light sources meet along a straight line the light is everywhere doubled and of equal strength, because where one ray has its apex the other has its base, as marked n m.
On this page
Luminous rays and their extremes
The heading announces a study of luminous rays and the 'powers of their extremes' — how the strength of light varies along a ray and at its ends.
Two eyes observing a line
A diagram shows two eyes observing a horizontal line, annotated 1 2 4, examining how the ray's power is distributed as it is viewed.
Two equal rays doubled in power
Where two rays issuing from equal lights meet along a straight line, the resulting ray is everywhere doubled and of equal power, because where one ray tapers to its apex the other spreads to its base, as shown at n m.
Crossed-line ray construction
The rays are drawn as crossed straight lines annotated 1 1 - 2 and 1 4 - 1-4, giving a geometric construction of the pyramidal (triangular) distribution of a ray's power.