204 On mppose.d Lunar Projecliles, 



passing near them, than by the sun; but this transient disturbance 

 may be very far from sufficient to prevent its continuing in its 

 orbit, though for a single evolution it may retard or (according 

 to circumstances) acce/era/e its return. 



It is further to be considered, that the projectile force acting 

 at the moon must be exceedingly great to throw the body eveu 

 15 or 2Q semidiameters oi \\\e moon, and may be such as instead 

 of ever carrying it to the earth would carry it in a parabolic or 

 hyperbolic curve immeasurably beyond the earth. And that it is 

 therefore perhaps not too much to suppose the probabilities 

 many miUions against one, against a lunar projectile ever being 

 80 thrown under such circumstances, of its direction and rate of 

 motion, and the position both of the earth and moon, as would 

 admit of its falling to the earth. It would rather /a// back to the 

 moon, revolve about the moon, or about the common centre of 

 gravity both of that and the earth. 



I doubt whether the sound v/cxG connected with the phcenome-> 

 non of Sth Dec* (7"^ l2| Astr. &c.) If it had, the meteor being at 

 least 3S" al)ove the horizon might have been seen to break ; — it 

 was above 60 at its greatest altitude. Its sudden disappearance 

 might be owing to extinction (See W. Hume's Essay, p. 87.) 

 or to very rapid motion in a line receding from the earth. That 

 it was either a gaseous body, or kindled different gases in its 

 passage, appears highly probable from its beautifully and variously 

 colourtd light. 



If a meteoric body of the iron kind, I believe we may say that 

 two miles height above the eartli is a very moderate supposition. 

 And then, if it subtended an angle of about equal to the moon, 

 its reaZ diameter at that distance will be found about 44 feet. 



And an arc of 60° being near = rad., supposing its path to 

 have been twomiles, if it described it in S" this is aquarterof amile 

 for each second, or 1320 f. 15 miles per min.; 900 by the hour, 

 If in 5"it would be nearly double of this velocity, 1056 x 2 = 21 12f. 

 per second. 



Observations are unfortunately wanting in other places which 

 might have determined its parallax : and consequently its height 

 in the atmosphere, magnitude and velocity. 



Most of the excellent rules of Dr. Maskelyne that are of chief 

 importance, seem conformable to the mode in which this obser- 

 vation was taken, and has been reported. I regret that I missed 

 seeing so beautiful and interesting a spectacle. 



Permit me, before I close this, to add a word or two on co- 

 mets. 



I need not say to you that the foreign papers, especifdly the 

 French and Gerwian, including Piussia, give, or used to give, the 

 • See Phil. Mag. for December last, p. 4Ci). 



rate 



