1868.] f^23 [Chase. 



TIDAL RAINFALL OF PIIlLADELrillA. 



Bead July 11th and October 2d, 1868. 

 By Pliny Earle Chase. 

 I hjive already given a portion of tlie evidence which indi- 

 cates a tendency- to increase of rain at quadrature and decrease 

 at syz3'g3\ In order to ascertain how far tluit evidence may be 

 confirmed or modified b}^ otlier considerations, it seemed de- 

 sirable to undertake a more general examination and comparison 

 of observations. The data for such an investigation were de- 

 rived from the following sources : 



1. The meteorological register of the Pennsylvania Hospital at 

 Philadelphia, covering a period of forty-three and a half years, 

 from January 1,1825 to July 1, 18G8. This register was in 

 charge of Newberry Smith from 1825 to 1828, of Franklin 

 Smith from 1828 to 1831, and of Dr. John Conrad from April 1, 

 1831, to the present time. 



2. The published record, in three octavo volumes, of five 3'ears' 

 observations at Girard College, Philadelphia, from June 1, 1840, 

 to July 1, 1845. 



3. The register of Prof. James A. Kirkpatrick, of the Central 

 High School, Philadelphia, from July 1, 1851, to July 1, 1868. 



4. Mr. Glaisher's summary of six years' hourly observations 

 of the rainfall at Greenwich, England, in the Proceedings of the 

 [British] Meteorological Societ}', A'ol. IV. No. 33. 



5. Mr. Dines's discussion, in the same Proceedings (Yol. IV. 

 No. 3G), of fort}' 3'ears rainfall at Cobham Lodge, Surre}', Eng- 

 land. 



6. Blodgett's tables of monthly rainfall at thirty-seven sta- 

 tions in AVestern and Southern Europe, and nineteen stations in 

 Central Europe and Asia.* 



7. Loomis's table of monthly rainfall at forty-fiive North 

 American stations. f 



In the preliminary comparison the Hospital observations were 

 arranged in weekly gronps for each quadrature and syzjgj, and 

 for each apsis, the critical day in each group being the mid day 

 of the seven. They were also arranged according to the moon's 

 latitude and declination. From the results of this comparison, 

 which are given in Tables I — III., as well as from the portions 



* Climatology of the United States, pp. U4-j. 

 t Treatise on Meteorologj', pp. 278-9. 



