with storms. When the atmospheric
pressure is decreasing, when with that there is increasing warmth and
moisture, and when south and southwesterly winds prevail, then ozone
is active; but when the atmospheric pressure is increasing, when the
air is becoming dry and cold, and north and northeasterly winds
prevail, then the presence of ozone is less active. These facts have
also been put in another way, namely, that the maximum period of ozone
occurs when there is greatest evaporation of water from the earth, and
the minimum when there is greatest condensation of water on the earth;
a theory which tallies well with the idea that ozone is most freely
present when electricity is being produced, least present when
electricity is in smallest quantity. Mr. Buchan, reporting on the
observations of the Scottish Meteorological Society, records that
ozone is most abundant from February to June, when the average amount
is 6.0; and least from July to January, when the average is 5.7; the
maximum, 6.2, being reached in May, and the minimum, 5.3, in November.
This same excellent observer states that "ozone is more abundant on
the sea coast than inland; in the west than the east of Great Britain;
in elevated than in low situations; with southwest than with northeast
winds; in the country than in towns; and on the windward than the
leeward side of towns."

Recently a very singular hypothesis has been broached in regard to the
blue color of the firmament and ozone. It has been observed that when
a tube is filled with ozone, the light transmitted through it is of a
blue color; from which fact it is assumed that the blue color of the
sky is due to the presence of this body in the higher atmospheric
strata. The hypothesis is in entire accord with the suggestion of
Professor Dove, to which Moffatt always paid the greatest respect,
viz., that the source of ozone for the whole of the planet is
equatorial, and that the point of development of ozone is where the
terrestrial atmosphere raised to its highest altitude, at the equator,
expands out north and south in opposite directions toward the two
poles, to return to the equator over the earth as the trade winds.

It is necessary for all who would understand the applications of ozone
for any purpose, whether for bleaching purposes or pure chemical
purposes, or for medical or sanitary purposes, to understand these
preliminary facts concerning it, facts which bring me to the
particular point to w