^ the scientific monthly, 555 
Ozone is not found in large quantity over marshes and swamps during the 
season of active decompqsition ^ vegetabie matter. 
TffE ^A.^E LOCALITy.' " ' ' 
The amount of ozone is not uniform in the same locality. In this State it is 
much more abundant in winter'than in summer. It is in inverse ratio to the tem¬ 
perature : as the temperature falls the ozone increases, and vice versa. For the 
greater part of the year there is more ozone by night than by day, but during hot 
weather this condition is reversed. 
It would be interesting to know whether the ni/ht air of summer is so much- 
more unhealthy than that of winter because of this deficiency of ozone by night 
’ in summer. It is stated that the air over the Dismal Swamp of Carolina is so 
loaded with miasm during warm weather, that passengers in the railroad cars at 
night are almost certain to contract malarious disease if they ride with th^ car 
windows open. It would be very interesting to know the amount of ozone over 
the Dismal Swamp by night during the summer months. 
The amount of ozone which is present in air at any one time is very small. 
According to Houzeau the maximum amount of ozone, even in country air, is 
only one part by volume in 700,000, or one part by weight in 450,000. 
HOW OBSERVED AND RECORDED. 
There are several tests which may be employed to detect the presence of 
zone. Of these I prefer the Schonbein test, because it is the most sensitive, and 
ecause the wide variation of the tint enables us to distinguish small variations in 
e amount of ozone, and thus secure a number of degrees in our scale. 
The Schonbein test paper is prepared by adding ten parts of best quality of 
rch to 200 parts of pure water, heating this till the starch gelatinizes, and then 
solving in this one part of pure iodide of potassium (free from iodate). This 
te is then spread evenly with a flat brush on sheets of paper free from sizing, 
ch are then rapidly dried by stove heat, without exposure to sunlight, and 
I stored up in a covered jar and kept from exposure to light. 
I make two observations a day, viz.: A “day observation” from 7 a. m. to 
M., and a ‘‘night observation” from 9 p. m. to 7 the next morning. I make 
)bservation by taking a slip of test paper one-half inch wide and four inches 
moistening the paper by rapidly dipping it into pure water, arid then pin- 
-^riing it up where it will be screened from sunshine, but freely exposed to diffuse 
daylight and to the air. I moisten the paper before exposure because ozone does 
V,. /^ot form or does not act on perfectly dry substances. At the close of the obser¬ 
vation, I dip the paper into clear water, and compare it with the ozone scale. 
This is drawn on a scale of ten, varying from the lightest perceptible tint 
of purple to the deepest purplish blue of iodide of starch. To fix the ob¬ 
servation, ascertain what portion of the scale most nearly corresponds in tone 
with the prevailing color of the moist test paper. In making this observation, I 
consider iho. prevailing color oi the test paper, disregarding the exceptional spots or 
I 
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