30G 
RKVliaV. 
Tliis conditional state of oxygen in the air is induced by 
electricity. Certain electro-chemical decompositions also 
give rise to it, and but for this agency the atmosphere would 
ultimately become incapable of sustaining life. 
There are several tests for its presence, and— 
“ Numerous observations made by these means in various countries, 
and by various experimenters, have shown that ozone is most abundant 
at the surface of the ocean and on- the tops of mountains, and that it is 
easier of detection when the air is in motion than when calms prevail, 
durinnr north and east than durinf; south and west winds, and in winter 
than in summer, especially during falls of snow. It has never been 
detected inside inhabited houses. In many instances, wliile the interior 
of a dwelling has afforded no trace of its presence, the external air close 
to the windows has manifested it abundantly. Ozone is not found under 
the shade of the forest. The absence of it from such places has led to 
the supposition that the currents of electricity which pervade the atmo¬ 
sphere, being diverted and conducted to the earth by the walls of houses, 
and the branches and trunks of trees, ozone has no opportunity of being 
produced in those situations, or, if there evolved, that it is immediately 
neutralized by the presence of oxidizable matter. A marked coincidence 
has been observed between the prevalence of certain types of epidemic 
disease and the absence or scantiness of ozone in the atmosphere. 
During the cholera of 1854, ozone was daily detected all round London, 
whereas no trace of it could be perceived in the more densely populated 
parts of the metropolis wliere the disease prevailed. On elevated ground 
it was generally present, but absent in low lying localities. A markeil 
diminution in the indications implying the presence of ozone has been 
very generally observed to precede the outbreak of an epidemic, while 
the reappearance of those indications has been found to form a very 
reliable sign of the abatement or cessation of the pestilence.’^ 
This is an important fact, since the original source and 
the medium of propagation of zymotic diseases are involved 
in considerable obscurity, but there are ample grounds for 
affirming that they are closely connected with foul and un¬ 
wholesome conditions of men, and of their food and habi¬ 
tations. 
“ While we sometimes see the equilibrium between the purifying 
power of the atmosphere and the contaminating effects of bodily ema¬ 
nations upset by an undue development of the latter, in the midst of 
conditions of ventilation which are usually highly favorable, at other 
times we must suppose similar results to be produced by meteorological 
causes, which temporarily diminish the neutralizing properties of the air. 
Of the latter kind of influence we have, perhaps, an example in the 
remarkable deterioration which sometimes suddenly occurs in all the 
wounds and sores in an hospital, without any assignable cause being 
apparent, except a marked and unfavorable atmospheric change. In 
certain low-lying, densely crowded, and ill-drained localities, in which 
those two antagonistic influences may be so equally balanced as to afford 
no opportunity for the development in excess of the morbific side of the 
scale, some adventitious change in the electrical conditions of the atmo- 
