effluent is a controversion of Section 20 of the Rivers Pollution Prevention Act, 1876, and consequently is actionable, the owners of the layings have a right of action at common law on account of the injury to their industry which takes place. The latter is not infrequently caused either by the discharge of the sewage in the vicinity of the beds, or in such a situation that the sea currents will carry it thereto.

Where these conditions prevail, periodical examination of the water should be made, as the sewage may contain the specific organisms of water-borne disease, some of which, as the typhoid bacillus, the causation of typhoid, or enteric fever, are most virulent in their character. The latter microscopic germs have been the cause on many occasions of the outbreak of severe cases through the consumption of contaminated shell fish.

The importance of protecting these layings is recognised, and need not be further emphasised.

We shall notice that legislative action is contemplated, with a view to ensure the protection of edible shell fish layings. In the meantime, it should be incumbent on all local authorities, whose districts are situate in their vicinity, to ensure that every care is exercised in the choice of an outfall. In connection with this latter, it is necessary to bear in mind that in the case of effluents, if they are imperfectly purified, they may be the means of carrying disease germs; and this may even be so with effluents of the highest standards. Whether the liquor in question is from septicised or chemically-treated sewage makes no practical difference in this respect.*

Effects on Sea Water of Discharge Therein.

The actual effect on the salt water into which crude water-carried sewage or sludge is discharged is still a matter of much controversy, and further extended experiments are necessary before any definite and final solution of the question

can be arrived at.

From the experiments of Professors Adeney, Letts, and others, on the effects produced by crude water-borne sewage,

* This may be a suitable place to mention that vegetables, watercress, and fruits grown on the ground should not be cultivated in any situation to which crude or unsatisfactorily-treated effluents may gain admission, because of any pathogenic organisms therein which may thrive and multiply. It must be borne in mind that large quantities of excrementitious matter need not, of necessity, be the causation of infectious disease cases, and the proximity of one or more isolated dwellings, or of fields to which cattle gain access, may be responsible.

when discharged into the sea, or an estuary, it would appear that this method of disposal is not so hygienically sound as has been thought. The influence of the salts present in the sea water, although the latter is very much greater in volume than the sewage flow, is not productive of a very speedy oxidation of the varied organic solids contained in the sewage, and as the growth of the organisms, which bring about the process of nitrification, is impeded, it is considered by some to point to the need for prior treatment of the crude water-carried sewage, with a view, as far as practicable, to destroy those compounds which exercise such an inhibitory influence on the usefulness of the nitrifying bacteria.

On the other hand, it is of interest to compare the influence of sea water itself on sewage sludge. From the evidence of Professor F. Clowes, D.Sc., before the Fifth Royal Commission, it would appear that the sea water has but little action as regards its interference with the life of the bacteria. Of necessity, it causes a very considerable diminution in their number, due to the vast volume of sea water into which the sludge is discharged, and which speedily breaks it up into innocuous pieces, and thus prevents any pollution in the water. In such cases, therefore, it is only a question of conveying the sludge sufficiently far out to sea, and away from the influence of the incoming tides, in order that no nuisance may be created on the shores in the vicinity. Whether the sewage is discharged in its crude form from an outfall on shore, or as siudge from a hopper at sea, the matter is usually the means of attracting many seagulls, which settle upon it immediately it is discharged into the water. It is preferable in the case of sludge that the dumping area should be carefully chosen, so that the neighbourhoods of edible shell-fish layings are avoided, and in order that they shall not be affected by the action of the incoming tides; further, that no nuisances should be created by their action through the conveyance of offensive matter to neighbouring shores.

Seaweeds and Sewage Discharges.

Volume II. Appendices, Part I. of the Royal Commission on Sewage Disposal (issued August, 1911), contains the minutes of evidence and reports to the Commission in reference to growths of green seaweeds in sewagepolluted estuaries. Its subject-matter possesses, at least, a three-fold aspect, because not only has it a bearing upon the discharge of crude sewage, or imperfectly purified

effluent into estuaries, and the possibility of detrimentally affecting the waters therein and the shores upon which the various currents may carry it, but there is the consequent interference with the amenities of communities and private owners, the pollution of any edible shell-fish layings, and infringement of the provisions of the Rivers Pollution Prevention Act, 1876.*

The inquiry and experiments in question were consequent on a serious effluvium nuisance which had occurred for many years in Belfast Lough. The sewage of Belfast has, for a prolonged period, been dealt with by screening and sedimentation, and turned into the Lough, together with crude sewage. The nuisance has appeared to coincide with this period, and was not apparent before.

Extended observations and experiments established the fact that the nuisance could be referred entirely to rotting green seaweeds, the chief of which belong to that class of marine algae known as the Ulva latissima. It appears that their growth is remarkable during spring and summer in sewage-polluted sea water, and fresh ulva taken from mud banks in Belfast Lough (the chief nursery there of these algæ, where the water flowing over is polluted to the extent of 1 per cent. with the sewage of Belfast) was found to contain over 4 per cent. of sulphur, as compared with 0.46 per cent. in sewage sludge.

It is interesting to note that this class of green seaweed is not peculiar to any particular neighbourhood, but is present also in the sea in the vicinity of the Giant's Causeway and on the Devonshire coast, and elsewhere round the British Isles, as well as on the Continent. Further, the presence of the Ulva latissima is evidence of sewage pollution. Its luxuriant growth is due to the presence of sewage-polluted water, as is evidenced by its great increase in parts of Belfast Lough since the pollution of the Lough by sewage. At the same time, it seems clearly established that purified sewage is also conducive to the growth of ulva. Hence the complex nature of the subject.

A decidedly interesting feature in connection with the Ulva latissima is that they require something to which to attach themselves, and this anchorage has been found to be usually other than mud, and generally on rocks or other solid bodies. This class of marine algae also shows a predilection for the shells of mussels (either dead or alive). The live

* See p. 292.

mussels usually attach themselves to the ulva by "byssus' threads, which they throw out. Mussels are often found in polluted waters. Indeed, they seem most prolific therein, and appear deliberately to attach themselves to the Ulva latissima.

Professor Letts suggests some sort of symbiosis of the ulva and the mussel, that the ulva gets its nutriment partly from the excreta of the mussel, and that the mussel eats the small creatures which are attracted by the ulva.

In situations where sewage effluents have to be discharged into sea water, there seems every indication that the removal or destruction of mussel beds will bring about the prevention of the growth of the ulva (for the production of which they form great nurseries), and thus prevent their annual rotting and consequent nuisance. Farmers occupying lands in the vicinity of the ulva growths in Belfast Lough take a certain amount of it away in carts to put on the land as manure.

The difficult point to determine, however, is the means to employ to get rid of the mussels. Experiments at Belfast with sulphate of copper, on an area of 37 acres densely covered with mussels, and where ulva had commenced their annual growth, had no lasting effect. Where, however, mussels were buried in trenches in situ, the particular area has, in the words of Mr. H. A. Cutler, M.Inst.C.E., the Belfast City Surveyor, "practically ceased to be a nursery for growing weed, and that the organic mud has disappeared."

But

With regard to the effect of clearing off mussels, in greatly reducing the growth of Ulva latissima, Southend is an interesting and useful case in point. For, as a result of such clearance, the ulva was washed away by the tides. The subject is one to which much knowledge has been added by the investigations of the Royal Commission. its labours should by no means end with the Report just issued. for it is a matter of much importance to all sanitary authorities whose areas are situate on estuaries and the sea coasts where sewage effluent is discharged, as well as to riparian owners and proprietors of edible shell-fish layings so situated.

CHAPTER XXIX.

The Fifth Royal Commission and the Pollution of Rivers and Streams.

The dangers arising from the admission of crude sewage or imperfectly-treated sewage effluent from sewage disposal works into streams have been placed by the members of the Fifth Royal Commission on Sewage Disposal, in their Fifth (1908) Report, under the following heads :-The de-aëration of the water of the river, with consequent injury to fish; the putrefaction of organic matter in the river to such an extent as to cause nuisance; the production of sewage fungus and other objectionable growths; the deposition of suspended matter, and its accumulation in the river bed or behind weirs; the discharge into the river of substances, in solution or suspension, which are poisonous to fish or to live stock drinking from the stream; the discoloration of the river; and the discharge into the river of micro-organisms of intestinal derivation, some of which are of a kind liable, under certain circumstances, to give rise to disease.

The specific organisms of typhoid or enteric fever, and other water-borne infectious diseases, come especially under this heading, and, from the standpoint of public health, the presence of pathogenic (disease-producing) bacteria in potable waters, and in those devoted to edible shell-fish layings or watercress growing, are likely to be the causes of serious outbreaks of typhoid or other water-borne infectious disease. The discharge of crude sewage, or insufficiently purified effluent, into streams is also most likely to be the causation of nuisances, especially in hot weather, by undesirable growths, or otherwise, and thereby constituting a danger to public health, which cannot be lost sight of.

With all the advances which have been made, both in chemical and bacteriological knowledge, since previous Commissions of inquiry into methods of sewage disposal and their influence on the pollution of streams, the last appointe Commissioners have reluctantly to admit that of all the various processes advocated for sewage treatment, or for the purification of water polluted by excrementitious matter, not one can be considered sufficiently satisfactory to warrant its