TRANSACTIONS OF THE SECTIONS. 7/ 



on the large scale, the carbonate of lime being derived from the solid excreta. The 

 evil exists in many houses where it is long unsuspected, and it shows that lead 

 pipes are quite unsuitable for conveying liouse excreta. 



Dry System. — None of these disadvantages can be urged against the dry closet, 

 still less can any serious evil attend its use, for it meets every sanitary requirement. 

 Its machinery- is simple and eilective, cheap in first cost and in use. It effects at 

 once a great saving of water, and it enables us to secure the whole value of the 

 excreta. 



"When dry earth is used, the onl}' objections to its adoption in large cities are, — 



1. The difficulty of obtaining the supply of diy earth, three and a half times the 

 quantity of the excreta being required. 



2. The cost of removal, involving the carriage of -3i times the weight of the 

 excreta into the city, and 41 times its weight out. 



Both these difficulties are at once removed by the use of charcoal, of which only 

 one-fourth the quantity, as compared with earth, is required; and given a stock to 

 commence with, by reburning the product the supply of charcoal is obtained from 

 the excreta itself. It is not necessary to reburn it after each use ; for dry closets it 

 may be dried and used again five times before being reburned, and for urinals alone 

 it may be used ten times. The reburning is conducted in apparatus which admits 

 of collecting the ammonia, acetic acid, and tar, which distil over, in the usual 

 condensers. 



The whole of the ammonia is thus collected, whilst the phosphoric acid, potash, 

 and mineral matters accumidate in the charcoal, together with the carbon, from tlie 

 organic constituents of the excreta. The weight of the charcoal is increased to the 

 extent of about 5 per cent, with each use ; and if dried and re-used five times, about 

 25 per cent, with each reburning. 



With this constant addition the charcoal does not require replacing with fresh 

 materia], the ultimate result being that the excreta are absorbed and deodorized by 

 a charcoal derived from itself. Thus a city working this process would, in addi- 

 tion to securing the whole of the ammonia and other products of destructive dis- 

 tillation, become sellers of a charcoal second only in value to that from bones, the 

 product in fact of disintegrated bone and muscle. A city of 500,000 inhabitants, 

 for instance, would produce 19 tons a day, or (3935 tons a year — tlie total quantity 

 of excreta to be removed being calculated at 385 tons a day, and its value at 

 29s. Qd. a ton = £568. The ultimate result being the same, any charcoal may be 

 used at first, but that from seaweed is preferred as the best and the cheapest. 



Attention is drawn to the fact that in such a population as that referred to the 

 fat passed in the solid excreta would amount to 7 tons a day ; and this would 

 appear among the fatty oils of the tar, and form another of the products recovered. 



Starting with seaweed charcoal, a lengthened series of experiments with urine 

 were imdertaken, the results of which were tabulated. The same charcoal was used 

 100 times, and reburnt 10 times, dm-ing which it had increased 183 per cent., and 

 given oft' ammonia equal to 316 per cent, of sulphate. The tables show the 

 increase of potash, phosphoric acid, &c. for each reburning, the phosphoric acid 

 appearing as phosphate of lime. The charcoal, containing at first 20 per cent, car- 

 bonate of lime and 5 per cent, phosphate, gradually decreases the carbonate to 

 2 per cent., and increases the phosphate to 25 per cent., at which it remains sta- 

 tionary, forming a sugar-refiner's charcoal. The phosphate of lime thus gradually 

 deposited is equal to soluble phosphate for manurial purposes, from its finely 

 divided condition. 



The results of a series of experiments -wath a dry closet were also tabulated. The 

 quantity of charcoal used was only 48 oz., to which 18 oz. were added after, the total 

 amount employed being 66 oz. ; the amount at the end of the experiment was 

 123 oz., 57 oz. having been derived from the excreta ; this small stock had served 

 181 uses, and_ absorbed 808 oz. of mixed excreta, having been dried and returned to 

 the closet 17 times, and reburnt 10 times. The analyses show this to be a prolific 

 source of ammonia, the average yield of sulphate being 7 per cent, of the wet ex- 

 creta, and 31 per cent, of the dry. The vaeld of acetate of lime was 4 per cent., and 

 of tar 9 per cent, of the dry excreta. A portion of the ammonia is combined with 

 acetic acid. The chars become uniform at about 24 per cent, phosphate of lime, 



