4 
HOUSEHOLD BACTERIOLOGY. 
Ingredients 
of Dust 
Movements 
of Dust 
comes through open doors and windows. Few win¬ 
dows and doors are so tightly fitted that fine dust will 
not sift in round their casings. 
Until electricity is made the common source of heat 
and light, there will be much dust from coal and wood, 
both before and after they are burned. These sources 
are too evident to need more than a mention. It is 
from the wear and tear of the house itself, its finish and 
furnishings, from our own bodies and the clothing that 
covers them, that the larger amount of dust comes. 
From these we have bits of wood, stone, cotton, hair, 
dead cells from all animal bodies—a mass of mineral, 
animal, and vegetable matter of very complex compo¬ 
sition. 
Since time began, everything in this old world has 
thus been wearing away more or less slowly, adding 
bit by bit to similar accumulations, until what we 
know as soil has been built up—pure mineral soil made 
from the debris of the rocks; organic soil or loam from 
the addition to this mineral soil of vegetable and ani¬ 
mal debris. The same processes are continually going 
on all about us. 
The dictionaries recognize this process when they 
tell us that dust is “Earth or other matter in fine dry 
particles so attenuated that they can be raised and car¬ 
ried by the wind.” 
Winds then are the responsible agents for much of 
the dust in our houses, but wind is simply air in mo¬ 
tion. We cannot walk across the floor, make a bed, 
rock comfortably in a chair, or dance a jig without 
