Bee's wax becomes bleached by exposure to the sun and dews in a similar manner as metals become calcined or rusty, viz. by the water on their surface being decomposed; and hence the inflammable material which caused the colour becomes united with vital air forming a new acid, and is washed away. Oil close stopped in a phial not full, and exposed long to the sun's light, becomes bleached, as I suppose, by the decomposition of the water it contains; the inflammable air rising above the surface, and the vital air uniting with the colouring matter of the oil. For it is remarkable, that by shutting up a phial of bleached oil in a dark drawer, it in a little time becomes coloured again. The following experiment shews the power of light in separating vital air from another basis, viz. from azote. Mr. Scheel inverted a glass vessel filled with colourless nitrous acid into another glass containing the same acid, and on exposing them to the sun's light, the inverted glass became partly filled with pure air, and the acid at the same time became coloured. Scheel in Crell's Annal. 1786. But if the vessel of colourless nitrous acid be quite full and stopped, so that no space is left for the air produced to expand itself into, no change of colour takes place. Priestley's Exp. VI. p. 344. See Keir's very excellent Chemical Dictionary, p. 99. new edition. A sun-flower three feet and half high according to the experiment of Dr. Hales, perspired two pints in one day (Vegetable Statics.) which is many times as much in proportion to its surface, as is perspired from the surface and lungs of animal bodies; it follows that the vital air liberated from the surfaces of plants by the sunshine must much exceed the quantity of it absorbed by their respiration, and that hence they improve the air in which they live during the light part of the day, and thus blanched vegetables will sooner become _tanned into green_ by the sun's light, than etiolated animal bodies will become _tanned yellow_ by the same means. It is hence evident, that the curious discovery of Dr. Priestley, that his green vegetable matter and other aquatic plants gave out vital air when the sun shone upon them, and the leaves of other plants did the same when immersed in water, as observed by Mr. Ingenhouze, refer to the perspiration of vegetables not to their respiration. Because Dr. Priestley observed the pure air to come from both sides of the leaves and even from the stalks of a water-flag, whereas one side of the leaf only serves the office of lungs, and certainly not the stalks. Exper. on Air, Vol. III. And thus in respect to the circumstance in which plants and animals seemed the furtherest removed from each other, I mean in their supposed mode of respiration, by which one was believed to purify the air which the other had injured, they seem to differ only in degree, and the analogy between them remains unbroken.