12(5 Mr. N. S. Maskelyne on the Pitted 



normal and two tangential, and that the normal axis differs 

 more from the others than they differ from one another. 



Some kinds of starch have grains of more irregular shape 

 than those treated of ; but their optical effects may be explained 

 in the same manner. 



This conclusion seems to agree with that arrived at by 

 Nageli and Schwendener : see Sach's ' Textbook of Botany,' 

 p. 588. 



24 Hyde Terrace, Leeds. 



XVII. The Pitted Surface of Meteorites. 

 By N. Story Maskelyne, F.R.S. fyc. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 



IN the Comptes Rendus for April 24th of this year M. 

 Daubree, the eminent director of the Ecole des Mines, 

 has offered an explanation of the hollows which characterize 

 the crusted surface of meteorites. This explanation he partly 

 draws from the very singular parallelism between this alveolar 

 surface of meteorites and that presented by the fragments of 

 unburnt gunpowder that fall at some distance from the muzzle 

 of a large piece of ordnance. 



I had myself the pleasure of introducing this subject to the 

 notice of my friend M. Daubree when he was staying with me 

 in London in the summer of last year. I drew his attention 

 to the remarkable similarity which these incompletely burned 

 fragments of gunpowder bear in the pitted character of their 

 surfaces to meteorites, whose black crust presents hollows and 

 irregularities curiously identical in feature with those of the 

 powder fragments. 



I spoke, indeed, with some hesitation as to the causes of this 

 similarity in the two cases, as the conditions were by no 

 means identical. Had M. Daubree's explanation been in all 

 respects in accord with what seemed and seems to me the 

 most satisfactory way of accounting for phenomena so similar, 

 it would be unnecessary for me to make any further observa- 

 tion on the matter. 



I should merely have been anticipated in the publication of 

 one of the points I have discussed in a little treatise on 

 meteorites long nearly ready for printing. 



Since, however, M. Daubree does not give the same ex- 

 planation of the hollows pitting the surface of a meteorite 

 that still appears to me to be, on the whole, the best way of 

 accounting for them, I venture to put on record, earlier than 

 I otherwise had intended doing, what I conceive is the pro- 



