Chapple. — On the Disposal of Sewage. 517 



the wood. This hole has been cut with a blunt instrument, 

 and not drilled. The inside is quite rough, and no attempt has 

 been made to smooth it. I cannot think that the hole would 

 have been cut through the wood if it had been meant to catch 

 the dust rubbed off by a fire-drill ; and unless this were done 

 no fire would be obtained. It seems to me 'that this piece of 

 wood is part of a whare, and that the hole is simply for a flax 

 lashing. However this may be, I am quite confident that 

 neither of these pieces of wood was meant for a fire-drill, and 

 that the rubbing apparatus found in the same cave was the 

 only means by which the moa-hunters obtained fire. 



Art. LX. — The Disposal of Seioage by Application to the 

 Soil (Setvage Farming). 



By Dr. Chapple. 



[Bead before the Wellington Philosophical Society, 28th June, 1893.] 



No subject in preventive medicine has attracted more atten- 

 tion or excited greater interest of recent years than the 

 efficient disposal of sewage. And such a statement in the 

 domain of science embodies the promise of great developments 

 — developments which have been abundantly realised — in this 

 important branch of public hygiene. Facts and experiences 

 have been accumulated from the numerous disposal- works in 

 England and Scotland, and theories have been elaborated in 

 laboratories, schools, and congresses, all tending .to place the 

 whole subject on a sound scientific basis. 



The purification of sewage by the soil is a chemico- 

 biological process; the working of a sewage farm, a sanito- 

 agricultural process. 



The term " soil " in its widest sense includes the superficial 

 layer of the earth's surface, and its properties, of course, vary 

 vastly. But all soils are common in this : that they contain 

 air, bacteria, and organic matter in varying proportions. Air 

 is most abundant in loose sand and friable loam, while organic 

 matter and bacteria are to be found most largely in rich loamy 

 soil. The bacteria of the soil are most numerous near the 

 surface, and exist in diminishing numbers to a depth of 3ft. 

 or 4ft. Their constant function under ordinary circumstances 

 is to disintegrate the particles of soil and of organic material 

 for the supply of plants with nutriment. These miniature 

 tillers of the soil require an abundance of both air and organic 



