Of Light and Colours.

If these lueific Particles are sufficientlyImbibed or generated in any opake Body,they cause it to shine, • or glow, or be-come red-hot; and by their prodigiousActivity will in Time disunite, dissolve,And destroy its natural Texture, and thuschange its Form, and reduce it to anotherSpecies of Matter; even the AJbeJios notExcepted (CXIII).

(CXlll) i. That Heat , Fire , Flame , &c. are only*he different Effects and Modifications of the ParticlesLight, is, I think, very evident; and the Particles°f Eight themselves depend entirely on Velocity for their^cific (Quality ; since by many Experiments we knowthat the Particles of Bodies become lucid, or Particles°f Light, by only .producing in them a requisite DegreeVelocity; thus the Particles in a Rod of Iron, be-* n g hammered very nimbly, shine and become red-hot;thus also the violent Stroke of the Flint against theSteel, in striking Fire, puts the Particles of the Steeltvhich it takes off" into such a Motion as causes them

to melt, and become red-hot, which makes the Sparks°f Fire produced by each Stroke. The fame Thingyou may observe in many other Cafes.

2. As Fire consists in the great Velocity of the Par-oles, so it may be communicated from one Body inMsich it is to another in which it is nbt, after the lamePlanner that one Body in Motion will communicateMotion to another Body that has none. Fire differsP'°m Heat only in this, that Heat is a Motion in theParticles of a Body with a lesser Degree of Velocity ;

Fire a Motion with a greater Degree of Velocity,t ’ i ~. such as is sufficient to make the Particles shine,^ugh we often, call such a Degree of Heat as will, Ur n, Fire, though it does not actually shine; and wetoldorn call those lucid Bodies Fires which only shineT 4 and

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