I should not wonder if, considering all this, we were induced to think that nothing remained to be added; and yet we are still very ignorant in regard to the internal construction of the sun.... The spots have been supposed to be solid bodies, the smoke of volcanoes, the scum floating on an ocean of fluid matter, clouds, opaque masses, and to be many other things.... The sun itself has been called a globe of fire, though, perhaps, metaphorically.... It is time now to profit by the observations we are in possession of. I have availed myself of the labors of preceding astronomers, but have been induced thereto by my own actual observation of the solar phenomena.

Ch.4 "Life and Works" quote from his paper "Nature and Construction of the Sun and Fixed Stars" (1795). - Sir William Herschel: His Life and Works (1880)