A ship was fitted up, instruments packed, the ocean crossed, a site selected and the telescopes mounted.

Scientists made all things ready for that opportune time when the sun and Venus and earth should all be in line.
That critical moment was very brief.

Instinctively each astronomer knew that his eye must be at the small end of the glass when the planet went scudding by the large end.

Once the period of conjunction had passed no machinery would offer itself for turning the planet back upon her axis.

Not for astronomers only are the opportune times brief.