Introductory. 



eflFectually by its application to land." The pre- 

 sent commission say (First Report, § 8, July, 1901) : 

 " Since the publication of the last-mentioned re- 

 port it has been the practice of the Local Gov- 

 ernment Board to require, save in exceptional 

 cases, that ' any scheme of sewage disposal for 

 which money is to be borrowed with their sanc- 

 tion should provide for the application of the 

 sewage or effluent to an adequate area of suit- 

 able land before its discharge into a stream.' There 

 can be no doubt, in our opinion, that the Local 

 Government Board were bound, under the circum- 

 stances, to insist upon such a rule." 



Lastly, the advent of bacterial processes for 

 the purification of sewage has had far-reaching 

 effects. Not only have many installations been 

 erected throughout the country, but attention has 

 been redirected to land treatment. It is now clear 

 that much of the work performed in the land is 

 due to bacteria, and sewage farms need no longer 

 be conducted by rule-of-thumb methods. Dr. 

 Houston, in the introductory remarks to Part III., 

 draws attention to the fact that the biological 

 qualities of land effluents were unknown, and states 

 that bacteriology has come to be considered an in- 

 dispensable adjunct to chemistry in the re-investi- 

 gation of the entire subject. While on this point 

 I would draw attention to the somewhat arbitrary 

 use by the commission of the term " natural " for 

 land treatment, and would ask if it is a natural 

 process to apply to the surface of land thousands 

 of gallons of water per acre, so that the many 

 impurities contained therein, and, be it noted, arti- 

 ficially introduced, may be removed. Again, if 

 land treatment be natural, why, in the early days 

 of irrigation, was that process deemed a menace to 

 public health? 



The question, " Are some sorts 



Suitable ^nd °* '*"'* unsuitable for the puri- 

 Unsultable. fication of sewage," is answered 

 as follows : " We doubt if any 

 land is entirely useless, but in the case of stiff 

 clay and pent lands the power to purify sewage 

 seems to depend on the depth of the top soil. 

 There are, of course, numerous gradations in the 

 depths of top soil which are met with in nature, 

 and it is not easy to draw the line between lands 

 which contain a sufficient depth to justify their 

 use and lands which do not. We are, however, 

 forced to conclude that peat and stiff clay lands 



are generally unsuitable for the purification of 

 sewage, that their use for this purpose is always 

 attended with difficulty, and that where the depth 

 of the top soil is very small, say, 6 in. or less, 

 the area of such lands which would be required 

 for efficient purification would in certain cases be 

 so great as to render land treatment impracticable." 

 (First Eeport, §15.) "We have considered it de- 

 sirable to publish, at this stage, the results and 

 information which have been obtained by our own 

 officers in regard to land treatment of sewage 

 and methods of analysis, but we shall defer re- 

 porting on these matters until our investigations, 

 which are now in progress, in regard to other 

 methods of sewage treatment, are completed." 

 (Fourth Report, § 117, December, 1903.) 



Lines 

 of Inquiry. 



The work for the commission 

 was undertaken by the follow- 

 ing gentlemen: Dr. Houston 

 (bacteriologist). Dr. McGowan (chemist), and Mr. 

 G. B. Kershaw (engineer). Part I. (Fourth Re- 

 port, vol. iv.) is a general report (116 pages), Part 

 II., chemical (328 pages). Part III., bacteriological 

 (214 pages), and Part IV., engineering and prac- 

 tical (129 pages). The blue-books are illustrated 

 by maps, plans, diagrams, micro -photographs, &c. 

 The general scope of the inquiry is thus stated in 

 the introduction : — 



" Having been instructed by the commission to 

 inquire into the subject of the land treatment of 

 sewage, we proceeded to visit a large number of 

 sewage farms throughout the country. During 

 our inspection of these farms we paid attention 

 to the following points, among others — namely : — 



" (I.) The general character of the soil and sub- 

 soil, and whether the original surface soil had been 

 ' lightened ' by ashes or other substances, or 

 ' treated ' with chalk. 



" (II.) Whether or not the land was drained, and, 

 if so, the nature of the drainage arrangements. 



" (III.) Whether the land was cropped, and, if so, 

 the nature of the crops. 



" (IV.) (a) Whether the whole of the crude sewage 

 (liquid and solid together), or (6) the settled 

 sewage after subsidence in tanks, or (c) the 

 sewage after chemical precipitation and settling, 

 or (d) the effluent from some other artificial process 

 of sewage treatment, was being run on to the land. 



