Sentence:  At 8h 35' 4", the least dent possible, quite black, appeared in the sun's limb. And at 8h 35' 6", the limb was restored to its perfect form, there having been a small trembling light, between the narrow watery border of Venus and the <WSD>vanishing point</WSD> of contact in the sun's limb for these two seconds of time. 
Meaning of the word marked with <WSD> tags:  The situation in which, place where, or point in time when some object or phenomenon is no longer observable or notable.