The Sanitary Engineer and the Public Health. 
58 
present are of a harmless kind, for in no recorded cases were pathogenic 
varieties present, while those that were found were not at all similar to 
those in sewage, being all air borne varieties instead of water borne. 
The chemical analyses showed, however, a considerable amount of free 
carbonic acid gas, for the oxygen of the air in the sewers had been largely 
consumed in the transformation of the organic matter present. Certain 
examinations showed that there was a little more of this carbonic acid 
present than in a crowded Boston theatre, the latter in one case amount- 
ing to a little more than one-half of one per cent. It is doubtless due to 
this gas, as well as some others, not considered as poisonous, that the 
continued breathing of sewer air may lower the tone of the constitution 
and thus make one an easier prey to disease. Fish die in water much 
polluted with sewage, but it has been conclusively shown that it is the 
absence of air that kills them, not the nature of the sewage itself. 
Laborers who work in sewers have been found to enjoy rather better 
health than the average, and in England many of them have worked for 
thirty or forty years at this business. At the Barking Creek outlet of 
the old London Main Drainage System the houses of the operatives were 
built over the 9-| acre reservoir that held the sewage for twenty-four 
hours, the reservoir being arched over and sodded. Notwithstanding 
they were directly over a lake of sewage, the people who lived there were 
healthier than those who dwelt in the crowded portions of the city. I 
am not advocating the liberation of sewer air in the vicinity of oneA 
living or sleeping apartments, but merely wish to show that the danger 
is not nearly so great as people usually think. Moreover, it can be 
effectually excluded by a proper system of plumbing and care in the use 
of fixtures. 
The work of the sanitary engineer includes the collection and disposal 
of garbage, which by putrefaction is likely to contaminate the air in 
cities. If it be not permissible to dump the garbage into tide water, and 
this should only be done at a sufficient distance from land to prevent the 
currents from returning it to the shore, the organic matter in garbage 
has either to be destroyed by cremation or by digestion. It was not 
until 1880 that furnaces for cremation purposes came into use. Their 
introdu'ction into America having occurred in 1885 at army posts. The 
digestion method is of even later date. With the cremation method the 
organic matter is entirely wasted, its destruction being the end sought, 
but the digestion method furnishes commercial products in the form of 
products condensed from the vapors, grease and a solid product called 
tankage that has a commercial value as a fertilizer. The dark colored 
liquid that is drawn from the digestors contains much organic matter, 
but no bacteria, these having been killed by the heat. It may become 
seeded with them again, however, and for this reason should not be dis- 
