Note 6 — PART I.
Reading edition
To investigate rules for this purpose, 1. Let M represent the mould candle, a its distance from the wall, on which the shadows were compared, x its quantity of matter consumed in a given time, (t) and Q the quantity of light emitted by M in the same time: 2. Let m represent any other candle, b its distance from the same wall, and y its quantity of matter consumed, in the time t.
Then as the intensities of light are directly as the squares of the distances of the two candles from the wall, we have as a2 : Q ∷:: b2 : b2 + Qa2 = the quantity of light, emitted by m in the time.
Then let us suppose that the quantities of light are directly as the quantities of matter consumed in the time t, and we have, As x : Q ∷:: y : y + Qx = the quantity of light emitted by m in that time, by hypothesis.
Now, when b2 + Qa2 (Theo. 1.) is = Y + QX (Theo. 2.) the quantities of light of M and m are directly as their quantities of matter consumed in any given time.