September 1832 was occasioned by the approach of Biela's Comet. De Morgan pertinently remarks that, "With a burning Sun overhead we have heard those who might have known better accusing the comet in the manner aforesaid."
Arago's article contains a statement of the mean temperature of every year from 1803 to 1831 inclusive; and side by side is placed the number of comets visible in each year. Inspection of the table conclusively shows that there is no connection between the two things. Thus 1806 and 1811 were both hot years; the first, however, hotter than the second, though the first had only one comet of no note, whilst the second had two comets, one of which was of remarkable brilliancy. Again, 1826 with its 5 comets was not nearly so warm as 1831 with its one comet. That hot years have in general more comets than cold ones is very true, and for the simple reason that hot years generally giving clear skies are more favourable for the discovery of comets than cold years, which so often mean cloudy skies. Nor must it be forgotten that the greater number of comets are not visible to the naked eye. Thus all the years between 1803 and 1831 inclusive, the temperature of which exceeded the average, mustered 29 comets between them; and the remaining or cold years only 15. It is therefore more reasonable to say, not that the comets brought the heat, but that the heat brought the comets. I have not thought it worth while to attempt to bring these figures up to date by comparing the temperatures of the years 1832 to 1909 with the comets of those 78 years; but that would be a suitable occupation for anybody who is fond of shooting the air. I cannot doubt what the result of such a research would be.
French writers on scientific subjects are very fond of interweaving with their facts a large mixture of fancies and romance. Jules Verne and F. A. Pouchet are types of what I mean. No wonder, therefore, that Astronomy is not exempt from that sort of thing. Accordingly we find that Guillemin, who with Flammarion may be taken to represent in French literature the department of Astronomy, is not behind his fellow-countrymen in sensational writing. In his book on
