 Some modern writers have criticised this approach on the grounds that Rumford's experiments in no way represented systematic quantitative measurements.In one of his personal notes, Joule contends that Mayer's measurement was no more accurate than Rumford's, perhaps in the hope that Mayer had not anticipated his own work.Joule has been attributed with explaining the sunset green flash phenomenon in a letter to the Manchester Literary and Philosophical Society in 1869; actually, he merely noted (with a sketch) the last glimpse as bluish green, without attempting to explain the cause of the phenomenon.