Owing to some remarks of Cicero, Horace, and Seneca, it has been supposed that in ancient times Sirius was of red colour. Seneca says, "Nec mirum est, si terra omnis generis et varia evaporatio est; quam in cœlo quoque non unus appareat color rerum, sed acrior sit Caniculæ rubor, Nartis remissior, Jovis nullus, in lucem puram nitore perducto."[436] It is now brilliantly white with a bluish tinge. But this change of colour is somewhat doubtful. The remarks of the ancient writers may possibly refer to its great brilliancy rather than its colour. Al-Sufi says nothing about its colour, and it was probably a white star in his time. If it were red in his day he would most probably have mentioned the fact, as he does in the case of several red stars. Brown, however, quotes the following from Ibn Alraqqa, an Arabian observer:-- "I recognize Sirius _shining red_, whilst the morning is becoming white. The night fading away, has risen and left him, The night is not afraid to lose him, since he follows her." Schjellerup thinks that it is very doubtful that Sirius was really red as seen by Hipparchus and Ptolemy. But in an exhaustive inquiry made by Dr. See on the supposed change of colour,[437] he comes to the conclusion that Sirius was really red in ancient times. Seneca states distinctly that it was redder than Mars (see extract above), and other ancient writers refer to its red colour. It has been generally supposed that the Arabian astronomer Alfraganus, in his translation of Ptolemy's _Almagest_, refers to only five red stars observed by Ptolemy, namely, Arcturus, Aldebaran, Betelgeuse, Antares, and Pollux. But Dr. See shows that this idea is due to a mistranslation of Alfraganus by Plato Tibertinus in 1537, and that Ptolemy did not speak of "five red stars," but five _nebulous_ stars, as stated by Christmann and Golius. Ptolemy described Sirius as υποκιρρος, "fiery red," the same word used with reference to the other stars mentioned above. The change of colour, if any, probably took place before Al-Sufi's time. Dr. See says-- "Prof. Newcomb rejects the former well-authenticated redness of Sirius, because he cannot explain the fact. But the ink was scarcely dry on his new book on the stars, in which he takes this position, when Nova Persei blazed forth in 1901; and observers saw it change colour from day to day and week to week. Could any one explain the cause of these numerous and conspicuous changes of colour? Shall we, then, deny the changes of colour in Nova Persei, some of which were noticed when it was nearly as bright as Sirius?"[438]