NO. l8 SMITHSONIAN PYRHELIOMETRY — ABBOT AND ALDRICH 5 



of these comparisons for determining the constants of the various 

 Smithsonian pyrheliometers a : 



Date. 



1910- 

 1911- 

 1911- 



1911- 



1912- 



1911- 



1912- 

 1912- 



1911- 

 1911- 

 1910- 

 1911- 



1911- 

 1911- 

 1912- 

 1911- 

 1911- 

 1911- 

 1911- 



1912- 

 1912- 

 1912- 

 1912- 

 1912- 

 1912- 



-Apr 8 



-Jan. 25 



-Jan. 25 



-Dec. 6 



-Feb. 10 



-Jan. 20, 23, 24, 



-Nov. 8 



-Nov. 8 



-Jan. 19 



-Jan. 20 



-Apr. 8 



-Dec. 3 



-Mar. 10 



-Mar. 21 



-May 18, 20. 

 -Apr. 25 ... . 



-May 4 



-Dec. 18.... 



-Feb. 6 



-Sept. 28.... 

 -Feb. 10 ... . 



-Feb. 10 



-Mar. 7 



-Mar. n, 16 

 -Mar. 16.... 



Number 

 compari- 

 sons. 



Secondaries used. 



S.I. 1 

 S.I. 1 

 S.I. 1 

 S.I. 1 

 S.I. 1 



S.I. 2 



s.r. 2 



S.I. 2 



S.I. 3 

 S.T. 3 

 S.I. 4 

 S.I. 4 



Ratio 



Data for S.I. 5 given in preceding table. 



S.I. 6 

 S.I. 7 

 S.T. 8 

 S.I. 9 

 S.I. 10 

 S.l. 10 

 S.I. 11 



S.I. 12 



S.I. 13 



S.I. 14 



S.I. 15 



S.I. 16 



S.l. 17 



A. P.O. 8bis 

 A. P. O.81. is 

 A.P.O. 8bis 

 A. P.O. Sim 

 A.P.O. Sbis 

 A.P.O. 9 

 A.P.O. 8bis 

 A.P.O. Sbis 

 A.P.O. 8bis 

 A.P.O. 9 

 A.P.O. 8bis 

 A.P.O. 8bis 

 A.P.O. 9 



1.0327 

 1 . 0408 

 1.0032 

 1. 0130 

 1 .0013 

 0.9703 

 1.0044 

 1.0427 

 1 .0466 

 0.9777 

 1. 0491 

 i-035^ 

 0.9990 



Probable 

 error. 



.0017 



.0022 

 .0018 

 .0021 

 .0012 

 .0027 

 .0024 

 .0020 

 .0017 

 .0014 

 .0014 

 .00l8 

 .0011 



VARIOUS A.P.O. PYRHKLIOMF.TERS. 



1906 — Apr. 2 6 



1908- — Apr. 16, 29 I 9 



1908— May 28 I 13 



1910 — Dec. 8 5 



1910 — Dec. 13, 15 11 



1911— Jan. 19, 20, 23, 24 I 34 



1908 — May 22-Tune 3 75 



1909 — June i-Sept. 1 1 160 



1910 — May 17-Oct. 25 700 



1912 — May 4-Aug. 12 1 60 



A.P.O. V 

 A.P.O. V 

 A.P.O. V 

 A.P.O. V 

 A.P.O, V 

 A.P.O. V 

 A.P.O. IV 

 A.P.O. IV 

 A.P.O. IV 

 A.P.O. IV 



A.P.O. IV 

 A.P.O. VII 

 A.P.O.VIII 

 A.P.O. 8 

 A.P.O. 8bis 

 A.P.O. si, is 

 A.P.O. VII 

 A.P.O. VII 

 A.P.O. VII 

 A.P.O. VII 



1. 0615 

 1.0786 

 1. 0815 

 o . 7864 

 0.7969 

 0.7927 

 0.9905 

 0-9955 

 . 9892 

 o . 9892 



.0050 

 •0035 

 .0016 

 .0012 

 .0024 

 .0013 

 .0010 

 .0007 

 .0005 

 .0012 



In accordance with the above table, the following values are now 

 adopted as the constants of Smithsonian Silver Disk Pyrheliometers 

 Nos. 1 to 17, which have been furnished to the parties mentioned in 

 the table. The column headed " old value " gives the constant which 

 was furnished at the time of sending out the instrument or sub- 

 sequently when further data indicated some desirable change. These 

 old values are to be displaced by the new ones which we now give. 

 We believe that the new constants should enable observers to reduce 

 their results to a consistent scale differing probably by less than 0.5 

 per cent from the true scale of calories per square centimeter per 

 minute. 



1 Instruments which were broken in transportation are omitted from this 

 list. 



