( 52 ) 



is recorded too late because the eclipse began earlier than was expected 

 and in consequence took me by surprise. As an evidence that the 

 time of last contact was given too late there is an instantaneous 

 photograph of the sun (diameter = 10 cm.) taken at the very moment 

 when I gave the signal "top". This plate shows a small impression 

 on the limb of the sun. 



To enable me to compare the obtained results, Messrs. Th. Wulf 

 and J. D. Lucas kindly put at my disposal the results of their highly 

 interesting observations of the 2"^^ and the S'"^' contact, made at Tortosa 

 by means of sensitive selenium elements. (See for this Astron. Nachr. 

 N». 4071). They found: 



beginning of totality l''16"il58,6 

 end „ „ 1 19 6,9, 



which yield the following equations : 

 AR— Ar — 0.9G50 A«(_o — 0.2117 Acf(_G + 0.0004 AV<(-o - 



— 0.0039 A« A(f -f 0.0092 AM(_e = — 5".73 



AR — Ar -I- 0.3063 A«(_o — 0.9493 Arf(_o + 0.0105 AV(_o -f- 



+ 0.0069 A« Ad + 0.0012 AM(_0 = + 4". 10 



whence 



A«(_0 =-. + 6".42 + 0.653 {AR — Ar) 



Aff(-Q = — 1".76 + 1.404 {AR — Ar). 

 When we subtract the two equations A from each other we get : 

 A«(_o = + 7".238 + 0.465 A(f(_0 , 

 which agrees exceedingly well with the result of the chord equations 

 A« = + 7". 428 -f 0.465 Arf; but it also appears that it is impossible 

 to determine A«, Aö and AR — Ar separately from the combination 

 of the contact and chord equations. 



In the derivation of the tinal result we have accorded the same 

 weight = 1 to the results of the chord measurements and to those 

 of the contact determinations made by Wulf — Lucas, and the weight 

 h to my observations of the 2"*^ and 3''^ contact. Thus we tind, leaving 

 out of account the tirst and the fourth contact : 



Ai2 + Ar = + 1".07 — 0.02 {AR—Ar) 

 A«(_0 == + 6".66 + 0.66 {AR—Ar) 

 A(f(_o = - 1".65 + 1.42 {AR-Ar). 

 The last column of the chord equations contains the deviations in 

 the sense of observation — computation, which remain when we sub- 

 stitute these numerical values. The mean error of the iirst 25 obser- 

 vations (excluding the tirst) amounts to ± 2. "53 ; that of the last 35 

 (excluding the last) is ± 2. "21, 



