274- OBSERVATIONS OF THE ECLIPSE 



Fig. 1 in Plate VI, represents the total eclipse, I shall on- 

 ly remark, that the luminous ring round the moon, is exactly 

 as it appeared in the middle of the eclipse, the illumination 

 which is seen in the lunar disk, preceded 6" 8 the appearance 

 of the first rays of the sun. Two minutes previous to the 

 emersion, I had fixed my eye on the point from whence it 

 was to proceed, and as the field of the telescope did not em- 

 brace more than a third part of the disk, I could not observe 

 whether or not the circumference of the ring was diminished 

 on the opposite side. — In the part where the emersion took 

 place, the ring was illuminated by degrees, and the atmos- 

 phere was more dense and brilliant near the edge of the moon. 

 A little before the illumination of the lunar disk, I observed 

 a zone to issue concentric with the sun, similar to the appear- 

 ance of a cloud illuminated by the rays of the sun, and as it 

 is represented in the figure, the versed sine of which was very 

 nearly equal to that of the illuminated part of the moon. — 

 We have seen that the radius of the luminous ring was 221- mi- 

 nutes, the horizontal semidiameter of the moon deducting the 

 inflection 16' 23" 8, and the horizontal equatorial parallax at 

 the time of conjunction ^SO' 15". With these elements if 

 we suppose the ring to be the visible atmosphere of the moon, 

 it would follow, that the height of the lunar atmosphere, 

 would be 348 geographical miles above its surface, which is 

 fifty times more extensive than the atmosphere of the earth. 

 It will moreover appear, that such an atmosphere cannot be- 

 long to the moon, but must without any doubt belong to the 

 sun. 



If the moon possessed such an atmosphere, it would be ma- 

 nifested by a diminution of the duration of eclipses, and oc- 

 cultations. — We have seen that the diminution of the semidia- 

 meter of the moon resulting from the observations of this eclipse 

 is 2'' 5, by comparing it with various occultations which I have 

 calculated, the inflection appears to be 2", it may be the effect 

 of the irradiation of light, but supposing it even to be caused 

 by the horizontal refraction of the moon, we know that the 

 inflection is double the horizontal refraction. The horizontal 

 terrestrial refraction, is nearly 33', therefore the density of the 



