320 



• 



great prevalence of Ozone, the test is exannined, and renewed at 

 shorter intervals. 



On comparing the recorded observations for the past six weeks, 

 Prof. Rogers had been struck with what seems to be a fixed re- 

 lation between the direction of the aerial current and the amount 

 of Ozone prevalent at the time. As long as the wind has con- 

 tinued to come from Eastern or Southern points, he has found 

 the Ozone to be nearly or quite absent, but whenever the current 

 has changed to West or Northwest, the test-paper has unfailingly- 

 indicated its presence in considerable force. The rapidity and 

 amount of this effect has always been greatest when the wind 

 has hauled suddenly to West and North, and has blown violently, 

 but it has continued to manifest itself, although with slow abate- 

 ment, as long as the current held from this quarter. 



To illustrate this effect, Prof. Rogers referred to examples within 

 the present month, (February.) Thus, on the 11th, the wind 

 being light from W. by S. and S. W., there was no indication of 

 Ozone, and during the morning of the 12th, the wind continuing 

 from the same general quarter, furnished a like negative result. 

 About ] P. M., however, the current changed suddenly to N. W. 

 with a snow squall, after which it continued to blow in gusts in 

 the same direction until late at night. Two hours after this 

 change, viz : at 3 P. M., the test-paper was found to be charged 

 with Ozone to the amount of ^^ of the maximum of Schonbein's 

 scale, and at 10 P. M., a second paper which had been freshly 

 substituted for the former, gave -f^. Again, on the 15th and 16th, 

 the wind blowing from S. and S. by W. showed no Ozone ; 

 retaining the same general direction through the night of the 16th, 

 and part of the following morning, it gave a like negative result. 

 About 11 A. M. of the 17th, the wind hauled towards West, and 

 about 1 P. M., it began to blow strong from W. by N., after 

 which it continued gusty from this quarter and N. W. until late 

 next day. The test-paper hung out at 9 A. M. of the 17th, was 

 found at 1 P. M., or two hours after the change, to present Ozone 

 amounting to -^^ ; and another substituted at that time, showed 

 at 6 P.M., or five hours after, a change measuring more than ■^^. 



Although the observations thus far made have indicated the 

 prevalence of Ozone in connection with winds from W. and 



