COMET OF 1811. 



recorded. To ascertain, then, whether the comets really exercise 

 any influence on the temperature of the seasons, it is only neces- 

 sary to place in juxta-position the comets and the temperatures, 

 and to examine whether there be any correspondence between 

 them. 



This was accordingly done by M. Arago. The records of the 

 public observatories supplied the data necessary to make the 

 comparison during the century which ended with 1832, and the 

 result was that no correspondence whatever was discoverable. 

 Sometimes it happened that the years of greatest mean tempera- 

 ture were those in which several comets appeared ; in some they 

 were those in which none appeared. In some cases the years 

 signalised by the most remarkable comets were characterised by a 

 high, in some by a low mean temperature. Thus in 1737, when 

 two comets appeared, the temperature was lower than in the two 

 preceding years when none appeared. Of the twenty years 

 which commenced in 1763, the coldest, 1766, was that in which 

 two comets, one of which was remarkable for its splendour, 

 appeared. In an interval of 16 years, the warmest was 1794, in 

 which no comet appeared, and the coldest was 1799, in which two 

 were seen. 



But omitting further notice of the thermal character of parti- 

 cular seasons, let us see what was the general result of this inves- 

 tigation. Of 74 years, 49 were signalised by the appearance 

 of one or several comets, and 25 by their non-appearance. The 

 mean temperature of the former years was found to be 51. 6, and 

 that of the latter 50. 7, the difference being less than one degree. 



Again, of the 49 years in which comets appeared, a single 

 comet was seen in 25, and two or more comets in 24. If these 

 bodies produced any influence on the temperature, a difference 

 ought to be expected between the mean temperature of the latter 

 and the former years. It was found, however, that the mean 

 temperature of 25 years of a single comet was 51.6, while that of 

 the 24 years of several comets was 51.4, the difference being only 

 the fifth of a degree, and even that being against the influence of 

 the comets in augmenting the temperature. 



In fine, the complete discussion of the cometary and thermal 

 observations, continued through an entire century, fully estab- 

 lishes the conclusion that there exists no foundation whatever for 

 the popular opinion that the comets influence the seasons. 



6. Of all the eventualities which may arise out of the motion of 

 comets through the system, the least improbable and moreover 

 that of which the consequences are most difficult to foresee, is the 

 passage of the earth through the tail of one of these bodies. 



The comets are exceedingly numerous ; but few of them have 



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