Surface of Meteorites. 127 



bable cause of the variolar surface in the two cases, and in 

 what respects I find myself not in accord with the conclusion 

 of the Director of the Ecole des Mines. 



And I should here say that I have had, on more occasions 

 than one during the last two or three years, to thank my 

 friends Professor Abel and Major Noble for specimens of these 

 fragments of gunpowder as projected from the 35-ton and 

 80-ton guns at Woolwich, and that in the explanation I offer 

 of this part of the questions at issue my opinion has been 

 brought into its present shape by the free communication of 

 theirs, of which I trust it will be a fair representation. 



The fragments are generally about the size of a small nut, 

 and very irregular in form ; but where the original grain of 

 the gunpowder had a definite geometrical shape, this shape is 

 distinctly recognizable in the diminished fragment which 

 represents it. 



The surface of the fragment is usually covered with a sort 

 of irregular reticulation composed of hollows which, though 

 sometimes isolated and nearly hemispherical, more often are 

 seen to become confluent while remaining comparatively 

 shallow. Sometimes a surface is met with that is smooth and 

 unindented. Any one familiar with the aspect of a stone 

 meteorite (an aerolite) will recognize at once the similarity 

 of this description to that of the black incrusted and indented 

 surface of one of these curious bodies. Those who are un- 

 familiar with this very characteristic feature of a meteorite 

 can see it abundantly illustrated in the collection at the British 

 Museum. Such, I may add, is the resemblance of the gun- 

 powder fragment to a small meteorite, that three years ago, 

 when I placed one of these powder-grains in the hands of 

 Mr. T. Davies, the experienced assistant in the Mineral De- 

 partment at the British Museum, he exclaimed, " What a 

 beautiful little specimen of the Cold Bokke veldt meteorite ! 

 how remarkably well it is indented ! " 



One would suppose that such a similarity in the two kinds 

 of object must both be due to a similar cause, and the more 

 so as in each case we have an accompaniment of detonation 

 with enormous velocity and sudden differences of temperature 

 and pressure ; and yet this parallelism of cause may never- 

 theless not be quite so complete as is that of the effects in the 

 two cases. 



Among the many splendid services which Professor Abel 

 has contributed, not only to the War Department at Woolwich, 

 but at the same time to science, rank his studies, extended 

 over many years, of the various conditions for and results of 

 the combustion of explosive agents, including gunpowder. 



