ABSTRACT
There is an analogy between air and water as to their relative composition, for both may be produced from the combination of only two gases, and yet such products are not found in nature. Both, in like manner, have other component parts, which some call impurities, but which are so far essential to their constitution that they cannot be obtained for the use of man without them; and in both the quantity of these additional matters, and not their presence or absence, is the present test of pure and. impure air and water; or, as it would be much less unsatisfactory to say, of normal and abnormal air and water.
