58 Prof. Maskelyne Bfi^ Dr. Lang's Mineralogical Notes. 



factorily explained by the dust of the enamel after its separation 

 from the aerolite in its course, and the combustion of its iron, 

 sulphur, kc. ; perhaps, also, small fragments are splintered and 

 fly off by the same principle as the larger ones, and, partially 

 burning, become dust too. 



Following in the track of the body, this dust would soon, 

 however, linger behind it and hang in the air like a vapour-cloud, 

 as is often seen to be the case in the wake alike of a meteor and 

 of a meteorite. 



Finally, if the reports represent the successive concussions of 

 the air produced by the disruption of the aerolite (and reaching 

 the ear generally in the inverse order of their occurrence in time), 

 we must attribute the " thunder " that is so often described as 

 succeeding the reports, to the echo of the reports themselves. 



That a noise, the true extent of which is likely to be exagge- 

 rated, should be heard over so large a range of country as sixty 

 linear miles, is perhaps not so surprising when we consider the 

 distance to which a small cannon can be heard, even over a 

 surface of country teeming with obstacles and air-currents cal- 

 culated to impede the passage of the sound ; whereas from a 

 height of two or three miles in a still, clear air, the spread of 

 even a comparatively small sound over an area with a radius of 

 thirty or forty miles seems nothing astonishing. To me, at least, 

 who have heard the roar of a train between Shrivenham and 

 Swindon, as I stood, on a still night, in the station at Cirencester, 

 a distance of certainly nearly twenty miles, such a wide promulga- 

 tion of a sound in the air is no more difficult to understand than 

 it is to credit the assertion of our aeronauts, who a few months 

 back heard a musical instrument played on the earth when their 

 balloon was some three miles above the ground. That this pro- 

 pagation of the sound of a cannon or a train is not due to the 

 conduction of the earth, is proved by the fact that it is only in 

 certain states of the atmosphere, independent of wind, that it 

 occurs. 



The cause to which I have assigned the disruption of a me- 

 teorite, and the reports which accompany it, may also furnish 

 an explanation of the great size of some aerosiderites and sidero- 

 lites, as compared with that of the largest stones. The more 

 rapid conducting power of the metal, as well as its greater power 

 of resisting a divcllent force, would — perhaps after a first dis- 

 ruption — tend to prevent the repeated breaking up of the mass; 

 and this may be the case in many instances, notwithstanding 

 the fact that in others meteorites of this kind have fallen in 

 associated and perhaps dissevered masses or even in showers. 



