468 Royal Society. 
the paper that is used for these test-slips, every precaution having 
been taken to make it so. 
Results of observations.—The following Tables have been con- 
structed from observations made between the lst of May, 1859, and 
the 3lst of March, 1860. 
TABLE I, 
Mean amount of Ozone observed from Test-slips hung for twelve 
hours, both at night and in the daytime, in comparison with others 
hung for twenty-four hours. 
Papers exposed for | Papers exposed for Difference 
twelve hours. twenty-four hours, ayes oa 
During the month of i oe CS RE SSre cwentecoue 
Day. | Night. Pate Day. | Night. oo hours. 
1859. May.........{ O°4 13 0-9 Je 1:9 0:8 0-7 0-6 
Sune, ..dint 03 | 09 | O1 3) 1-5, se 05 | 06 
Tully... .éseck 09 | 10] O1 | 1:2 | 13 | O1 || 08g 08 
August...... 07 14 | 07 1:2 18 0-6 0-5 0-4 
September .| 1:9 2°6 0:7 2°5 30 0:5 0-6 O-4 
October ...| 095 0-7 0:2 0:7 0-9 0-2 0-2 0-2 
November..| 1:5 LZ, 0:2 1:8 2-1 0:3 0-3 0:4 
December...| 1°7 2:0 0:3 2-1 25 0-4 0-4 0:5 
1860. January ...} 2°38 | 2:8 | 0-0 So {oo o, | ees 0-4 | 07 
February ...| 273 2°8 0:5 2°6 3°0 0-4 0-3 0-2 
Marchicvens. 49 5:2 0:3 5-2 5°6 0-4 0:3 0-4 
Mean scsi: 17 2-0 0:3 2-1 2°5 0-4 0:4 0-5 
The ozone being always in excess in the night, and the tests exposed 
for twenty-four hours showing always an excess over those only ex- 
posed for twelve hours. 
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TaBxe II. 
Number of observations without any visible ozone. 
During the night. During the day. 
Month. 
Twelve hours’ | Twenty-four || Twelve hours’ | Twenty-four 
exposure. hours’ exposure. exposure. hours’ exposure. 
1859. May......... a 4 19 12 
VONE sexiness 18 10 15 9 
SLY chino ab 18 12 | 18 13 
August...... 10 4 15 9 
September.. 2 0 0 0 
October ... 16 12 18 14 
November.. 10 7 10 10 
December... 10 sf) 7 5 
1860. January ... 8 6 “, 5 
February ... 12 6 9 9 
0 0 0 
