Prof. Maskelyne and Dr. Lang's Mineralogical Notes. 139 



evidences of the presence of this substance in aerolites that do 

 not on a first scrutiny appear to contain it. 



There seems also to be in Manegaum a very small amount of 

 a transparent colourless crystalline mineral ; but whether it is a 

 distinct substance from the olivine-like ingredient, I am not 

 able at present to say. The specific gravity of the aerolite is 

 about 3-22. 



A remark or two may not be out of place here in respect to 

 the aerolites that are ascribed to the Howardite class of Rose. 



The only two besides Manegaum that I have had the oppor- 

 tunity as yet of scrutinizing present very important differences. 

 The Bialystok stone contains, to an amount by no means insig- 

 nificant, very distinct crystals of what I have little hesitation in 

 pronouncing to be an augite. It is a dark brown mineral with its 

 planes of polarization oblique to the crystal and to a well-marked 

 striation indicative of cleavage, and presenting a decided and 

 interesting similarity to the augite of Juvenas, Jonsac, Peters* 

 burg, &c* 



The other observation I have to make is, that the Howardite 

 kind of aerolite is not sui generis. In several aerolites belong- 

 ing to other classes, one meets with nodules and spherules, often 

 of considerable size, of aerolitic matter belonging strictly to this 

 " Howardite ;; kind. It is seen in Richmond, and forms a con- 

 siderable ingredient in Petersburg. It occurs also in Benares, 

 Marion County, and Nanjemoy ; and I have met with it in a 

 large nodule from the stone of Quenggouk, and otherwise disse- 

 minated in that aerolite; and this list will doubtless be consider- 

 ably extended. 



A fact like this may serve to warn us against the endeavour 

 to separate by too sharp lines of demarcation the different groups 

 into which a first inspection of their lithological characteristics 

 might induce us to divide the various aerolites in our collections. 



* Since the text was in the press, I have had an opportunity, through 

 the civility of Prof. Shepard, of inspecting a small fragment of the Noble- 

 borough stone. It is a curious aerolite. More like Bialystok than Mas- 

 sing or Manegaum, it is rich in a very black and opake substance (probably 

 two such substances, one of which is) like the dark augite in the Eukritic 

 aerolites, and especially in Juvenas. There is much of a colourless mineral 

 as well as of olivine, of every tint from pale yellow to yellowish brown ; and 

 the opake white mineral above alluded to is abundant. There is also a 

 small amount of iron, and of what seems to be tro'ilite. The crust is an 

 enamel with fine lustre. The transparent colourless mineral may possibly 

 be a felspar (anorthite?), but it requires further scrutiny. 



