Men who study the stars tell us strange and wonderful things-things that the unlearned find it hard to understand, and harder still to believe, yet things that we are now as sure of as we are of the fact that two and two make four!There was a time when men said that the sun moved round the earth; and very natural it was in men to say so, for, to the eye of sense, it looks as if this were really the case. But those who study the stars have found out that the earth moves round the sun-a discovery which has been of the greatest importance to mankind-though the importance thereof cannot be fully understood except by scientific men.Among other difficult things, these astronomers have attempted to measure the distance of the sun, moon, and stars from our earth. Moreover, they have tried to ascertain the exact size of these celestial lights, and they have, to a considerable extent, been successful in their efforts. By their complicated calculations, the men who study the stars can tell the exact day, hour, and minute when certain events will happen, such as an eclipse of the sun or of the moon.Now, about the year 1768 the attention of the scientific world was eagerly turned to an event which was to take place in the following year. This was the passage of the planet Venus across the face of the sun. Astronomers term this the Transit of Venus. It happens very seldom: it occurred in 1769, but not again till 1874, and 1882. By observing this passage-this transit-of Venus across the sun from different parts of our earth, it was hoped that such information could be obtained as would enable us to measure not only the distance of the sun from the earth with greater accuracy than heretofore, but also the extent of the whole host of stars that move with our earth around the sun and form what is called our Solar System.
