have been observed on the large partially burned grains of 

 gunpowder which have been picked up near the muzzle after 

 the firing of the 35-ton and 80-ton guns at Woolwich. The 

 pitting of the gunpowder grains is attributed to unequal 

 combustion, but that of meteorites seems to be due not so 

 much to inequality of combustibility as to that of conduc- 

 tivity and fusibility of the matter on the surface. 



The sudden generation of heat, and the consequent expan- 

 sion of the outer shell, account not only for the break-up of 

 the meteorite into fragments, but also for the crash like tJtat 

 of thunder which is a usual accompaniment of the fall. 

 Haidinger was, however, inclined to refer this noise, not to 

 the fracture, but to the sudden collapse of the vacuum which 

 is so quickly left behind in the early part of the course. In 

 the consideration of this question the Butsura fall of 1 2 th May, 

 1861 (285 PQ), is particularly interesting. The explosions, 

 in this case three in number, were heard 60 miles away at 

 Goruckpur. Fragments of the stone were picked up three 

 or four miles apart, and, "wonderful to say, it was possible to 

 reconstruct with much certainty the portion of the meteorite 

 of which they are the part. Two of them, in other respects 

 fitting perfectly together, are even on the faces of the junction 

 now coated with a black crust, showing that one disruption 

 took place when the meteorite had a high velocity; two other 

 fragments found some miles apart fitted perfectly, and were 

 neither of them incrusted at the surface of fracture, thus 

 indicating another disruption at a time when the velocity of 

 the meteorite had been so far reduced that the surface could 

 no longer be liquefied through the generation of heat. Some- 

 times, as at Orgueil, the fragments reach the ground before 

 the sound of the explosion is heard, proving that the break- 

 up has taken place while the velocity of the meteorite was 

 considerably higher than that of the sound vibrations (1100 

 feet a second). 



After the explosion are generally heard sounds which have 

 been variously likened to the flapping of the wings of wild 

 geese, to the bellowing of oxen, to the roaring of a fire in a 

 chimney, to the noise of a carriage on the pavement, and to 

 the tearing of calico : these sounds are probably due to the 



