Doubts and Facts concerning Linne. 37 



The results that have as yet been arrived at, and which 

 are supported both by English and Continental observations, 

 are as follows : — 



First. The existence of a shallow crater, usually presenting- 

 the appearance of a whitish cloud, which, by the way, is of 

 variable size ; the crater itself has been very rarely seen. 

 Respighi saw it on the 10th of May, 1867, during a perfectly 

 tranquil state of the air. Knott caught a sight of the ring on 

 January 12th, 1867, and, on the same evening, in moments of 

 quiet air and good definition, Buckingham noticed the shallow 

 depression. Webb saw the ring on April 11th, 1867. 



Second. In this shallow crater or depression, a little west 

 of the centre, a small crater with a well-marked interior shadow 

 has been seen more or less distinctly, both in England and on 

 the Continent, since November, 1866; in some cases as a 

 perfect crater, in others portions only have been detected. 

 The evidence tending to establish the existence of this small 

 crater is certainly beyond dispute. 



Third. Herr Schmidt, of Athens, carefully observed Linne 

 from October 16th, 1866, and during November, 1866, without 

 having detected either the large shallow crater or the small 

 one within it. The rim of the small crater appears to have 

 first arrested his attention on December 13th, 1866, as a 

 delicate white hill ; Buckingham seems to have first seen the 

 shadow as a black spot on the following evening, December 14th. 



In all former records of Linne nothing is said of two craters, 

 one within the other. Linne is simply described as a crater. 



In the older records the diameter of Linne is given by one 

 authority (Schmidt) as 1*5 German miles, and by another 

 (Beer and Madler) as 1*4 German miles. 



Since December 14th, 1866, the diameter of the white 

 cloudy mass has been measured nine times. Schmidt has given 

 two estimates of its extent, October 18th, 1866, at 2 German 

 miles, and December 27th at 2000 toises only. 



Three estimations of the size of the small crater have been 

 given; the first, 1867, February 11th, by Secchi, at most -^ of 

 a second. The second, some time in April or May, 1867, by 

 Respighi, viz., 4 seconds. The third, by Wolf, 1867, June 12, 

 at 1 second. These estimations differ very considerably the 

 one from the other. 



In cases of measurement the values were obtained in 

 seconds of arc. The estimations were in German miles, or 

 toises. 



As the value in miles, or English feet, of a second of arc 

 at the moon's apparent centre increases as the object is 

 removed from the moon's centre in the proportion of the 

 secant of the angular distance from the centre, it is easy to 



