DUBOIS, Les Passages de Vénus sur le disque solaire, 1873

First edition.
Work preparing the transit of Venus across the Sun in 1874.
The transit of Venus in 1874 was the first transit of the planet in the 19th century, eight years before the second in 1882. Like the transits of 1761 and 1769 in the previous century, these two transits give rise to numerous observations around the globe, in order to be able to precisely measure the value of the astronomical unit, the distance between the Earth and the Sun.