sort of phænomenon, never hitherto honoured with an adequate description. If it should appear to the Royal Society in the same light, they will excuse the trouble given on this occasioon by,

THESE remarks were wrote above a twelve-month ago, and would have been then communicaled to the Royal Society, had not my voyage to Barbados prevented it. Since my return from thence, I find part of the mistakes here pointed out acknowledged and corrected by M. Delalande, in his Treatise of Astronomy lately published, to whom I remember to have communicated my ideas on the subject, when he was in England. Nevertheless, as the error arising from