XXIX 



of '516 of nitrogen, and of '14 of soluble phosphoric acid in the 

 collected matter—that is, 200 tons were treated to get one ton of 

 nitrogen, and 700 tons to get one ton of soluble phosphoric acid. 

 At seems to have been impracticable to get at the real cost of the proeessj 

 out, seeing that it took more than two hours for the first treatment of 

 every ton of the collected matter, the nitrogen obtained must have cost 

 at least a quarter of its market price, and the phosphoric acid about 

 tumble its price. Now, if in Hobart there were collected a quantity 

 M matter, proportional in regard to population to that collected in 

 -Kochdale, that quantity would be about 2,600 tons a year, and the 

 quantity of nitrogen obtainable from it would be 13416 tons, and 

 ot soluble phosphoric acid 3-64 tons. These quantities show that the 

 only legitimate profit to be made out of the treatment of the Hobart 

 collection could not exceed a few hundred pounds a year, a sum that 

 Would be absorbed in interest on capital. And so no company could 

 attord to pay anything to the corporation in diminution of the cost of 

 collection. On the other hand, the cost, under a water-closet system, 

 is limited to the supervision of that class of houses where ordinary 

 closets cannot be entrusted to the occupants. In Hobart this super- 

 vision should not cost £1,000 a year. In the report it is estimated 

 at £1,600, as the whole of the calculations therein are largely liberal 

 80 as to be on the safe side. 



The following is a summary of the total cost of removing all the 

 sewage by the two systems :— 



Open Drainage. 



Interest on £20,000, cost of necessary works, at 4 per cent. £800 



Repairs on above at 5 per cent. 1,000 



Cost of gutter sweeping, exclusive of water 5,500 



Cost of pail collection and cleansing 9,000 



Tot al £16,300 



Underground Drainage. 

 Interest on £60,000, cost of necessary works, at 4 per cent. £2,400 



Repairs on above at 5 per cent. 3,000 



Cost of emptying trough closets 1,600 



Total .., £7,000 



Yearly saving of underground system £9,300 



m- • I W ^' observe that it is above taken for granted that the sewers 

 P ovided for removing house slops are taken as being also sufficient 

 Latli remt>V] ' n g water-closet sewage. This is so. As Mr. Baldwin 

 s . '"am says in the work already quoted : — "To what has already been 



ated it is only necessary to add that the introduction of the water- 

 set, with perfect water-waste preventing fittings, will not materially 

 he eaS i e *' le v °Jume of sewage for which provision will require to 

 of til as *^ e wa ter used for this purpose forms but a small part 



th t ?" e °f the water used for domestic and general purposes ; 

 thi , ore ' * n districts in which ashpits, earth-closets, or other devices of 

 the S ° aoter a ^ e used for collecting f ;ecal matter, it will be well that 

 in t f ame Provision should be made in the size of the sewers as is made 



nose districts in which water-closets are universally adopted." 

 Tj, .question of the disposal of the sewage remains to be considered. 

 w' e 's no doubt that where practicable it is desirable that sewage 

 cou ould be Purified before it be allowed to flow into a water- 



has^ 6 ' Up t0 the P rese nt the most satisfactory method of purification 



8 Been by surface filtration or irrigation. To carry this out properly, 



