A water with the utmost impunity, under certain conditions. few years ago the author proved that a town in Somersetshire had drunk a water-supply from shallow wells which was nothing more nor less than dilute sewage; and yet the death-rates from fever, from dysentery, and all other diseases supposed (and rightly supposed) to be propagated by water, were remarkably low in comparison with places drinking a pure water. Here, then, was an experiment ready made on more than a thousand persons, and the negative results recorded for the best part of a century. It proved that under ordinary conditions the water was harmless, and yet what chemist could pass such? The colour, taste, and smell, as well as the organic carbon, nitrogen, and microscopical characters, all combined to show that the characters of the supply were of great impurity; on the other hand, water of very moderate impurity, as shown by ordinary chemical and microscopical investigation, has many times been as fatal as a solution of some subtle poison. These, as it were, unconscious experiments continuously proceeding in towns, in villages, and in solitary homes, demand the closest study; and such a study will in years to come make clear the apparent discrepancy often existing between chemical and biological analysis. Possibly the conclusion already shadowed forth is this:-water, however polluted by healthy human or animal sewage, nasty and abominable liquid as it may be, will produce no disease; water infected with the excretions from diseased natures will cause disease. Since, however, at the present time we cannot differentiate between those excrementitious matters which cause disease, and those which do not cause disease, it is clearly safest to condemn as a supply a liquid which has been proved to be contaminated by a something, which, for aught we know, contains the seed of typhoid fever or of cholera. D. Experiments on Fish.—It is in some instances extremely useful to study the effects of water upon living fish, especially in those cases in which there has been raised the question of whether a river or stream is polluted to such an extent as to destroy the fish in the stream. In experimenting as to whether a given water will support fish, it is essential to select healthy fish, fish suitable for the experiment, and to let the experiment go on for as long as possible. The best fish are the gold fish and the minnow, one or both. These can in towns be always purchased, and there is scarcely any country place in England in which minnows are not procurable. Besides, more is known as to the action of impurities on these fish, than on any other. The substances destructive to fish-life may be arranged in regard to their power of destruction in four classes: 1. Sulphate of copper, the mineral acids; the sulphates of alum and iron, iodine, bromine, caustic potash or soda; the chlorides of tin, the heavy and light pitch oils, saturated solution of chloride of lime, and carbolic acid. These all destroy minnow life when contained in solution in so small a quantity as from 1:10,000, and some of them from 1: 100,000. 2. The next in order of destroying-power are such as garancine, madder, sumach, catechu, acetic acid, citric acid, arsenious acid, gallic acid. These are all fatal when existing in the proportion of from 1: 7000 of water, to from 1:3500. 3. The least destructive, but yet poisonous, agents are tartarie acid, salts of soda and potash, hydrate of lime, ammonia, bisul phide of carbon, sulphide of ammonium, sulphuretted hydrogen. foundry cake, furnace cinders, bleaching liquor. 4. Lastly come substances which are not directly poisonous. but induce a lowered vitality of the fish, so that it becomes attacked with a fungous growth. The author found that a residue from gas-works, consisting of phenol and a mixture of hydrocarbons, though in less than 1 part per 10,000 of water, yet induced the growth of a fungus in the course of a few days on minnows, dace, roach, and rudd. The experiment was repeated many times, and always with the same result. Organic matters, such as blood and urine, must be in a state of decomposition, and in such considerable quantities, that they deprive the water of oxygen before the fish are affected. Many oils appear to have no injurious effect on fish, as, for example, linseed and olive oil. Symptoms.-In solutions that are not only poisonous, but also irritating to the surface of the body, the fish make frantic efforts to escape, and will often jump out of the water, rising to a considerable height. In solutions of poisonous substances generally, the symptoms to be looked for are: projection of the eyes, the frequent rising to the surface to breathe, loss of natural balance, disordered movements, loss of agility, especially the allowing of little masses of food to pass by unobserved, and, lastly, lying on the side at the top of the water. § 321. Interpretation of Results.-On many samples of water it takes some experience to give a really correct judgment, and it must ever be borne in mind that it is most unsafe to trust to an estimation of one or two constituents only. The report must be based upon a valuation of all the determinations, and a careful consideration of the general tendency of evidence. Great assistance will be derived in this by the aid of a scale by which a definite numerical value is assigned to the component parts of an analysis. Such a scale has been invented by Mr. Wigner, and is now in provisional use by analysts. § 322. Valuation of Water according to Mr. Wigner's Scale.-In this scale, every constituent of the water as analysed by the Forchammer and ammonia processes has a definite value attached to it, and these values added together make the value of the water. It has been objected to the use of such a scale, that unless the history of the water is known, very erroneous conclusions may be drawn, and indeed it may be admitted that the scale is of far greater use in reports upon waters like the metropolitan, which are analysed from day to day throughout the year, than when operating on unknown samples. Nevertheless, there has always been a want of some definite expression of value, and as the scale is confessedly only a provisional one, the present writer thinks that it may be used generally with caution and discrimination. dark green, Suspended matter to be added to valuation of appearance. 0224 124 1241 Strong peaty, Offensive, of animal matter, Chlorine in Chlorides, *5 grs. per gal. = 1 large ·002 gr. ⚫010 gr. 5° 1 . 5 grs. per gal. = 1 H. =12 quantity, 62 6 12 Hairs, and animal débris, 10 to 20,' according to the quantity observed. The following table gives the chemical results of the several monthly analyses of the Grand Junction water by the author, with the values according to the scale attached. The microscopical observations are omitted, because they were for the most part negative, and the chemical determinations being more easily followed will serve as a better example. The diagram is a graphical representation of the purity of the water according to the scale value. It will be admitted that on no other principle could the purity of a water be depicted by a single curve : |