METEOROLOGICAL OBSERVATIONS AT PLYMOUTH. 155 



Table VII. 





Summer. 



Winter. 



Mean Pressure 



29787 



29^811 



Time of Mean Pressure 



A.M. 



P.M. 



A.M. 



P.M. 



h. m. 

 1 30 

 4 



h. m. 



7 

 10 



h. m. 

 25 

 4 



h. m. 

 6 30 

 10 



h, m. 

 2 

 4 



h. 



7 

 10 



m. 

 

 



h. m. 

 noon. 

 3 



h. m. 

 6 30 

 9 





Mean Oscillation 



•015 



•020 



Differences from T 

 Mean of Year J 



•0018- 



•0031 + 



The mean oscillation of winter by this table appears greater 

 than that of summer, whilst the critical hours of evening fall 

 an hour sooner. 



13. In Plate VII. is dehneated from Table III. the hourly 

 march of the pressure through a mean day of spring, summer, 

 autumn and winter, divided into periods of three months each, 

 and in the following Table are given the principal elements 

 of these oscillations. 



Table VIII. 



j Critical Hours. 



io 



10 







4 



10 oj 



5 



10 



4 « 



10 





9 



4 



10 





10 



3 



11 



Mean Oscillation. 



i 



•017 



•013 



•018 



•023 



Differences from Mean Oscillation of the Year. 



•0001+ 1 



•0038- 



•001 + 



■0061- 



It appears by this table that the mean oscillation of winter is 

 the greatest, and that of summer the least ; whilst the mean 

 oscillation of spring is not very different from that of the whole 

 year, the oscillation of autumn being a mean between sum- 

 mer and winter. 



