XXXIV GEELMUYDEN. ASTRONOMICAL OBSERVATIONS. [NORW. POL. EXP. 



For the determination of the hreadth of the invisible segment all obser- 

 vations of disappearances and reappearances in the years 1893 98, published 

 in the Monthly Notices and in the Astronomische Nachrichten, were exami- 

 ned, and those selected where the same phenomenon had been observed by 

 means of two or more telescopes of different aperture. Each pair of such 

 observations gave an equation, which was retained in the form of equation 

 (6) with a (which depends on the apertures) as coefficient of x, though it was 

 an unfavorable circumstance that most of the observations had been taken 

 with instruments so far superior to that of the Fram in regard of size, that 

 the weight of an equation was often much smaller than would have been 

 the case with a somewhat larger standard aperture. Some few observations 

 with large apertures differing only 1 or 2 cm. have been omitted. 



In the second column of the following Table a, containing the places of 

 observation, the following abbreviations have been used: Bs Bermerside, Ch 

 Christiania, Gr Greenwich, Gt Gottingen, Jn Jena, Ks Kasan, Ly Lyons, Po 

 Pola, Uc Uccle, Ut Utrecht. In some cases two observations with telescopes 

 of nearly the same aperture have been combined into one, which is indicated 

 by an added 2 or by a + between the places when they were different. Next 

 follow the apertures A t and A 2 in centimetres. Owing to the not uncommon 

 custom of giving, in astronomical publications, the aperture in inches of the 

 different countries, even where the metrical system has been introduced, the 

 last figure may in some cases be inaccurate; the fraction of cm. has been 

 retained here only when certain. The last column contains the quantity 

 10 ck (T 2 TJ which is designated by i. 



