123 



chanical and dissolved colouring impurities. The water, 

 though by this process rendered beautifully clear and 

 colourless, contains not a trace of any substance which was 

 not present in it before treatment. The process is already 

 extensively used both for the treatment of water supplies 

 for towns and manufactories, as well as for that of sewage 

 and other waste waters. 



Mr. Spence continued in harness to his latest years, ex- 

 perimenting almost daily in his laboratory, patenting all 

 radically new improvements of his processes, and generally 

 "bearing fruit in old age." The number of the various 

 patents taken out by him nearly equalled that of the years 

 of his life. 



As a citizen, Mr. Spence applied his extensive technical 

 knowledge to the solution of various sanitary problems 

 connected with life in towns. His well-known pamphlet 

 " Coal, Smoke, and Sewage " was the reprint of a paper read 

 before the Manchester Literary and Philosophical Society 

 over a quarter of a century ago, and had a very extensive 

 circulation. In this pamphlet the suggestion was made that 

 the sewers and house and factory chimneys of Manchester 

 should be connected with a colossal shaft 600 feet high, at 

 which elevation it was maintained that diffusion would 

 operate so powerfully as to prevent aU possibility of nui- 

 sance from the gases, to the population below. 



Its leading principle — fuel chimney ventilation of sewers 

 — has been increasingly applied of late years in a variety of 

 forms. Mr. Spence himself permanently cured two dwel- 

 ling houses, in which he resided in succession, of sewer gas 

 exhalations, by simply connecting the drains below the 

 house with the back of the kitchen chimney by a piece of 

 cast-iron pipe. By adopting the principle of chimney venti- 

 lation, Mr. Waterhouse, who consulted Mr. Spence in pre- 

 paring his plans, secured a continuous supply of fresh air 

 for the various rooms of the Manchester Assize Courts. 



