To make dim or indistinct
He also observed the eclipse of the sun on May 4, 1818.
foretold that there would be a solar eclipse in that year, as stated by Herodotus.
After a long eclipse it was finally re-established, though in a very modified form, by Alfonso Liguori about the middle of the 18th century.
The solar eclipse of 1748 made a deep impression upon him; and having graduated as seventh wrangler from Trinity College, Cambridge, in 1754, he determined to devote himself wholly to astronomy.
In 1860 De la Rue took the photoheliograph to Spain for the purpose of photographing the total solar eclipse which occurred on the 18th of July of that year.