64 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 90 



On January I, 1929, the hour of the afternoon observation 

 was changed from I4 h to I3 h , the morning and evening 

 observations remaining the same as since 191 1, viz., y h and 

 2i h , so that the formula for mean temperature was altered 

 to |(7 h +i3 h -f2i h + 2i h ) and for mean pressure l(7 h + 

 I3 h + 2i h ). On April 1, 1930, the hour of the evening obser- 

 vation was changed to i8 h for daily weather map purposes. 

 From April to December 1930 the temperature data sent 

 by the director were the mean of the daily maximum and 

 minimum values, along with a table of corrections for each 

 station to reduce to |(7 h +i4 h + 2i h -(-2i h ). In the case of 

 Santiago since 192 1, and at Magallanes after 1927, a further 

 small correction to reduce to the 24 hour mean had also 

 to be applied. It will be seen, therefore, that certain compli- 

 cations were set up in 1929, and again in April 1930, which 

 called for the computation of corrections so as to avoid any 

 line of discontinuity with the preceding observations. This 

 work was done by R. C. Mossman, with whom lies the final 

 responsibility for the accuracy of the data. 

 With regard to Punta Galera, Isla Guafo, and Islota de los 

 Evangelistos, the mean of the daily maximum and minimum 

 temperatures continued to be employed, so that no correc- 

 tions were required. Although the temperature means 

 i(7 h + I3 h + i8 h ) in use since April 1930 are not yet available, 

 the corrections are included so that when the 1930 "Anuario " 

 of the Oficina is published, there may be a further check- 

 on the values derived from the mean of the Max. and Min. 

 for the stations of Magallanes, Santiago and Juan Fernandez. 

 For these stations the data may be corrected in the manner 

 indicated to the 24 hour mean, or as in the case of Juan Fer- 

 nandez to the mean of ^(7 h +i4 h + 2i h + 2i h ). 



Pressure corrections to 24 hours in tenths of millimeters 



Station Hours of Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 



Observation 



Santiago* 3(7"+14 h +21 h ) -2-2-1 0-1-1-2-2 



4(7 h +13 h +21 11 ) -3-3-2-1 0-1-1-2-2-3 



J(7 h +13 h +18») 0+1+1+1+1 0+1 



Punta i(7 b +14 h + 21") 0-1-1 0-1-1-1-1 



Galera t 



£(7 h + 13 h +21 h ) -1-1-2—1 0-1 0-1-2-2-1 



£(7 h +13 h + 18 h ) + 2 +3 +2+2 +1 +1 +1 + 1 +1 +1 +2 +3 



* Derived from 5-year means at Santiago, 1911-1915. 

 t Derived from 2-year means at Isla Guafo. 



