74 



NA TURE 



\_May 26, 1887 



purification. Precipitation by chemicals implies certain 

 conditions. First, if you want to treat sewage properly 

 by a precipitation process, you must treat it fresh, before 

 active putrefaction sets in. Secondly, before you mix your 

 chemicals with it, you should strain the sewage in 

 some way or other. Thirdly, you should add sufficient 

 chemicals to effect complete purification. Fourthly, there 

 should be efficient stirring after the addition of the 

 chemicals. Fifthly, it is essential that you should have 

 sufficient tank accommodation, for two reasons : first, 

 that the precipitate may subside perfectly ; secondly, 

 that the sludge may be frequently removed. If you allow 

 the old sludge to remain in the tanks, it is perfectly 

 certain that it will contaminate the fresh sewage when 

 it comes in. When the sludge is taken out of the tank, 

 the tank itself must be washed. By combining precipi- 

 tation, which will produce a good effluent, with land 

 treatment or prepared filters, you may produce the best 

 effluent that is known. 



Intermittent downward filtration through land will ade- 

 quately purify sewage so as to allow the effluent to pass 

 into a stream ; but by this plan the manure which is so 

 much wanted is almost entirely lost, the greater part 

 escaping in solution in the effluent water in the form of 

 nitrates and nitrites. On the other hand, if the effluent 

 is used for irrigation farming, under necessary conditions 

 of soil and methods of application, the sewage is purified, 

 a certain agricultural return is obtained, and, provided 

 the irrigated land is placed at a sufficient distance (say 

 500 yards) from houses, rhe health and comfort of the 

 neighbourhood are not endangered. 



Dr. Corfield thus sums up his conclusions : — 



" Wherever it is possible, irrigation should be carried 

 out, the sewage having been previously freed, by one or 

 other of the methods described, from the offensive sus- 

 pended matters, which must be deodorised to prevent the 

 production of a serious nuisance. Wherever, on the other 

 hand, irrigation is practically impossible, intermittent 

 downward filtration through soil affords the means of 

 satisfactorily purifying the sewage." 



Drs. Corfield and Parkes say that these were the con- 

 clusions at which they arrived seventeen years ago, and 

 that they see no reason to alter them now ; but we much 

 doubt whether finality on this question of sewage-disposal 

 has been arrived at. The cremation of refuse on a system- 

 atic plan is of only a few years' standing, and at present of 

 somewhat limited application. Moreover, we stand on the 

 threshold of discoveries as to the more occult causes of 

 infection : we are learning daily much of the history and 

 habits of those lower forms of life which play so large a 

 part in putrefactive changes, and which are in some cases 

 proved to be baneful to us under the conditions in which 

 they now occur, but whose action we might possibly 

 learn to modify under enlarged knowledge. We have 

 recently seen how the extraction of oxygen from the atmo- 

 sphere has risen from being a toy to the position of a 

 practical art. These discoveries may eventually have 

 some bearing on the safe disposal of the refuse matter 

 which is continually being formed in the midst of dense 

 populations. During the last twenty years we have 

 made rapid strides in the methods of removal and 

 disposal of refuse, which have been the result of the free 

 development of the intelligence of the community in 



sanitary matters : each of those years has marked some 

 step of progress, and we continue daily to advance. It is 

 therefore to be hoped that Parliament will not accept the 

 views of those persons who seem now to be endeavouring 

 to stereotype by Act of Parliament our present position in 

 sanitation, as if it were perfection. Such a step might 

 seriously check future progress. 



THE POLYZOA OF THE "CHALLENGER'' 

 EXPEDITION. 



The Zoology of the Voyage of H.M.S. " Challenger" 

 Part XXX. "Report on the Polyzoa— Part II. The 

 Cyclostomata, Ctenostomata, and Pedicellinea." By 

 George Busk, F.R.S., &c. (Published by Order of Her 

 Majesty's Government, 1886.) 



THE first and second memoirs contained in Vol. XVII. 

 of the Zoological Reports of the Voyage of the 

 Challettger were reviewed in NATURE two weeks ago (p. 

 26). The third memoir, the subject of the present notice, 

 formed the last piece of scientific work of the distinguished 

 naturalist to whom the preparation of the Report on the 

 Polyzoa had been intrusted. During a period of illness 

 and suffering under which the energies of most men 

 would have broken down, Mr. Busk still laboured to 

 accomplish the task which he had undertaken, and it 

 was only a few days before his death that he was enabled 

 to bring it to a conclusion. 



The author deemed it advisable to divide the Report 

 on the Polyzoa collected during the great exploratory 

 voyage into two parts. The first of these has already been 

 reviewed in Nature (vol. xxxi. p. 146). It is confined 

 to the Cheilostomatous species, and includes by far the 

 greater number of all the Polyzoa collected. There still 

 remained for consideration such species as are referable 

 to the three remaining sections, namely, the Cyclosto- 

 mata, the Ctenostomata, and the Pedicellinea. Each of 

 these three groups has its representatives in the present 

 Part, but the number of these is small in comparison 

 with those referable to the Cheilostomata, and there does 

 not occur among them any generic form which can be 

 regarded as new. The account of them here given, while 

 it completes the Report on the Polyzoa collected during 

 the expedition, is characterized by all that careful and 

 exact work which invariably marked the scientific labours 

 of its author. 



The entire number of species included in the present 

 Part is forty-six, of which thirteen are now described for 

 the first time. Of these forty-six species the most 

 interesting are probably the two referable to the section 

 Pedicellinea, and placed by the author in his genus 

 Ascopodaria. The Pedicellinea form a very aberrant 

 group of Polyzoa, presenting characters which differ 

 widely from those met with in typical Polyzoal structure. 

 They are represented in our own seas by two or three 

 species of the curious genus Pedicellina, with its naked 

 pedunculated polypides destitute of the " cells " into 

 which the polypides of other Polyzoa admit of being 

 retracted. The genus Ascopodaria is rendered further 

 remarkable by the flask-like dilatation with muscular 

 walls which exists at the origin of each peduncle. The 



