196 
maximum of the horizontal movement of the air and of the 
fall of rain, and that the minimum of ozone occurred at the 
time of the minimum of the wind and rain-fall; and that in 
the summer months, when the horizontal movement of the 
air was at its minimum, ozone development was at its mini- 
mum too. 
The same rule will be seen to hold good on an examina- 
tion of the second table, particularly in the months of 
January, February, March, August, and December. In the 
months from May to December of 1868 more ozone was 
found than in the same months of 1867. But where this 
excess is not connected with high winds and heavy rain-fall, 
as in May, June, and July, 1868, heavy dews occurred 
during the nights, which will account for the excess of ozone 
in those months. 
The third table shows again that the excess of wind or 
rain-fall is attended with an excess of ozone development; 
though excess of wind seems to tend more to its develop- 
ment than the excess of rain-fall, which may be accounted 
for, as Professor J evons points out, by the convection of the 
lowest mass of the air during the day. 
The next tables, prepared from the elements of the same 
two years and from the number of days on which each 
amount of ozone was found, give the mean amounts of the 
horizontal movement of the air in miles, the fall of rain in 
inches, and the percentages of the general direction of the 
wind, reduced to the four cardinal points. Both these 
means and percentages are placed opposite to the amount of 
ozone to which they relate; and as these amounts are 
reckoned from a scale of estimation from 0 to 10 + , the 
amounts of ozone are indicated in the first column of the 
table. 
