MEMOIR ON METEORITES. 



307 



would be considered superfluous have been instituted to prove 

 the perfect fallacy of making any but a most erroneous esti- 

 mate of the size of luminous bodies by their apparent size, 

 even when their distance from the observer and the true size of the 

 object are known. How much more fallacious then any estimate 

 of size made where the observer does not know the true size 

 of the body, and not even his distance very accurately. 



In my experiments three solid bodies in a state of vigorous 

 incandescence were used: first, charcoal points transmitting 

 electricity; second, lime heated by the oxy hydrogen blow- 

 pipe; third, steel in a state of incandescence in a stream of 

 oxygen gas. They were observed on a clear night at different 

 distances, and the body of light (without the bordering rays) 

 compared with the disk of the moon, then nearly full and 45° 

 above the horizon. Without going into details of the experi- 

 ment the results will be tabulated : 



Carbon points 



Lime light 



Incandescent steel 



Actual diam. 



as seen at 



10 in. 



Inch. 



To- 

 4 



Apparent 



diameter at 



200 yds. 



Diameter 

 moon's disk, 



1 



Apparent 



diameter at 



% mile. 



Diameter 

 moon's disk. 



3 



2 



1 



Apparent 



diameter at 



■K mile. 



Diameter 

 moon's disk. 



2 

 1 



If then the apparent diameter of a luminous meteor at a 

 given distance is to be accepted as a guide for calculating the 

 real size of these bodies the 



Charcoal * points would be 80 feet in diameter, instead of ^ of an inch. 

 Lime •• 50 •• •• •• T % 



The steel globule •• 25 •• •• •• t 2 q 



It is not in place to enter into any exj)lanation of these 

 deceptive appearances, for they are well-known facts, and were 

 tried in the present form only to give precision to the criticism 

 on the supposed size of these bodies. Comments on them are 

 also unnecessary, as they speak for themselves. But to return 

 to the two meteorites under review. 



* Estimate made according to a table given by Prof. Olmsted ( Amer. Jour, 

 of Science and Arts, vol. xxvi, p. 155) for estimating the diameter of meteors 

 on comparison with the moon. 



