REVIEWS—DONATI’S COMET. 74 
We must refer to Arago for a grave discussion of the followin 
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questions: Do Comets sensibly influence the weather? Epicures 
know the ‘vintage of the comet-year,” and who has not read of the 
.... Comet, which with torrid heat, 
And vapour as the Libyan air adust, 
Began to parch that temperate clime. 
Were the dry fogs of 1783 and 1831, matter detatched from a 
comet's tail? Has the moon ever come into collision with a comet ? 
Has she herself formerly been a comet ? and if so, what has she done 
with her wig? What would become of us if the Earth were to be 
carried away as a satellite by a comet? In which case Arago holds it 
not proven that the human race would necessarily perish from thermo- 
metric changes, and this is consolatory. Has the axis of the Earth 
been shifted by the shock of a comet, and did not such a shock produce 
the depression of the large area in Central Asia? Lastly, what 
would be the effects of a collision between our Earth and acomet? In 
answer, listen to Laplace !—If the earth dashed against it, so that the 
motion in space should be stopped, all things not adhering to the 
earth’s surface, animals, water, &c., would fiy off it at a rate of 72000 
miles an hour. Even if the shock did not wholly destroy the earth’s 
velocity, still the axis of rotation would be altered, the seas would 
leave their beds and rush towards the new equator; in this universal 
deluge, animal and man would in great part perish, or would be des- 
troyed by the violence of the blow; entire species annihilated ; all 
the courses of human industry confounded, &c., &c. A horrible 
picture to contemplate! True,—we are comforted by the great virtue 
of the “if,’ and by the calculation that the odds are 281 millions to 
1 against the happening of the event. So, when the legendary 
militia-man with shut eyes fired his musket against the barn-door, 
the chances were millions to one against his hitting any assigned 
point ; nevertheless, some point was hit in spite of the enormous odds 
in its case; and when we know that Biela’s Comet cut the Earth’s 
path when she was only one month absent from that point, it must be 
confessed that the comet has come very close to us nothwithstanding 
our theory of probabilities. 
We have seen that Newton regards with complacency the admixture 
of a comet’s tall with our atmosphere. Herschel on the other hand 
thinks such a rencontre would be ‘‘not unattended with danger.” 
Probably in such matters it will be well to follow the advice of the 
