View report page

34
is shewn on Chart I. in orange colour, and is taken at 3 feet below
the surface, and it must be remembered that as depicted it is not the
maximum nor the minimum temperature, but, like the barometric
reading on this chart, it is the mean for the week. As shewn, I think
it clearly explains the fact that in the cooler months the earth is
warmer than the atmosphere, hence the soil and atmospheric airs
interchange.
At this period of the year typhoid fever is seen to prevail.
Roads and pavements being covered for the most part with
impermeable materials, the ground air, stagnant and possibly polluted,
would be drawn from great distances, entering those houses the sites
of which are not covered over with concrete.
One has only to look at the unpaved portion of the back yards in
houses of the poor where fowls, etc., are kept, and vegetable matter,
etc., are thrown, to think of how much ground pollution exists.
The London County Council's bye-law prohibiting any manure
receptacle being below the surface of the ground is certainly wise.
The bye-law relating to ash-pits is likewise highly salutary. The
provision of adequate or ample underfloor ventilation is also
good, more especially where the site of the premises is not
covered with an impermeable material. As to wood pavement,
I think after the report of the Analyst of Marylebone Vestry
to that body, that without a doubt wood pavement more or
less contaminates the air. In his report he states:—" That wood
blocks are by no means impervious, but get in time more or
less saturated with impurities—the centre of the road showing the
least contamination, the channels most contamination. It is curious
to observe that the centre block shows most ammonia in the top
layer, the amounts decreasing as you pass to the bottom; while the
channel block shows the reverse. The explanation is, I believe,
this : that the old wood blocks allow in the interstices between them
water to percolate on to the impervious sheet on which they are