every substance which is somewhat dry, is easily ignited, because there is less mingled with it of that which is a hindrance to ignition.
He infers that the substance which hinders ignition is moisture, but does not state this explicitly. Dryness is not the direct inverse of dampness, but might be of something else ( lacking some compound of hydroxide, for instance).
He is a bit too generous in stating "every substance ", as there may be some things that are, under all conditions, not flammable. I do not presently know of any examples as did not he.
