nature, and produced under a great variety of circumstances. During the excitation of an electrical machine, or the passage of a galvanic current through water by the oxidation of phosphorus, and probably in many similar processes--in particular those of combustion, and we may therefore infer also of respiration--this body is formed. From observations which have been made, it would appear that, during the night, when the activity of plants is not excited by light, they act upon the atmosphere in such a way as to produce this ozone; and its presence is said to be indicated by its peculiar odour during the early hours of morning. We are not yet acquainted with this body sufficiently to speculate on its uses in nature: without doubt, they are important, perhaps second to those of water only. It is probable, as we have already had occasion to remark, that ozone may be the active agent in removing from the atmosphere those organic poisons to which many forms of pestilence are traceable; and it is a curious fact, that a low electrical intensity, and a consequent deficiency of atmospheric ozone, marks the prevalence of cholera, and an excess distinguishes the reign of influenza.[214] Some interesting researches appear to show the probability that ozone is simply oxygen in a state of high activity. It has been found, indeed, that perfectly dry oxygen, which will not bleach vegetable colours in the dark, acquires, by exposure to sunshine, the power of destroying them. Becquerel has proved that this ozonous state may be produced in dry oxygen by passing a succession of electric sparks through it. Fremy passed the electric sparks on the outside of a tube which contained perfectly dry oxygen, and it was found to have acquired the properties of ozone. In this case, and probably in the experiments of Becquerel, the light of the spark, rather than the electricity, appears to have been the active agent in producing this change. Schönbein himself does not appear disposed to regard ozone as being either peroxide of hydrogen, or an allotropic oxygen. He leans to his first view of its being an entirely new chemical element. The energy of this ozone is so great, that it has been found to destroy almost instantaneously the Indian-rubber union joints of the apparatus in which it is formed.[215] Water, from the consideration of which a digression has been indulged in, to consider the curious character of one of its elements,--water is one of the most powerful chemical agents, having a most extensive range of affinities, entering directly into the composition of a great many crystallizable bodies and organic compounds. In those cases where it is not combined as water, its elements often exist in the proportions in which water is formed. Gum, starch, and sugar, only differ from each other in the proportions in which the elements of water are combined with the carbon.