Daguerreotype
It is said that Daguerre has found the means to collect, on a plate prepared by him, the image produced by the camera obscura, in such a way that a portrait, a landscape, or any view, projected upon this plate by the ordinary camera obscura, leaves an imprint in light and shade there, and thus presents the most perfect of all drawings ... a preparation put over this image preserves it for an indefinite time ... the physical sciences have perhaps never presented a marvel comparable to this one.
A further clue to fixing the date of invention of the process is that when the Paris correspondent of the London periodical "The Athenaeum" reported the public announcement of the daguerreotype in 1839, he mentioned that the daguerreotypes now being produced were of considerably better quality than the ones he had seen "four years earlier".
Daguerreotype
Niépce's early experiments had derived from his interest in lithography and centered around capturing the image in a camera (then called a camera obscura) to result in an engraving that could be printed somehow by lithography. The asphalt process or heliography required exposures that were so long that Arago said it was not fit for use. Nevertheless, without Niépce's experiments, it is unlikely that Daguerre would have been able to build on them to adapt and improve what turned out to be the daguerreotype process.