SECONDARY MINKRALS AND I:T( HIXGS 



277 



still unaltered, but their surfaces are deeply etched, pits and narrow 

 grooves cutting into the surfaces 3 or 5 and even to 15 mm. (see figure 11. 

 specimen TT616, and figure 12, specimen 88435). These markings \ary 

 in shape and size from semicircular grooves, which have been well chai- 

 acterized as lunar crater forms by ({. P. ^Ferrill,^' to straight channels 

 not unlike the marks left bv an enufraver's tools. The distribution of the 

 various markings, both it-giihii' and ii'i-i-giilai'. follows no discerniblr oi'ilcr; 

 and the (piestion of the mode of foi'niation of such remarkable etch 

 phenomena is of interest esjiecially heeause of the siniilnritv (d' these 



Fn;i Ki: 11. — Ijiciiril Snrftuc of (ihshlimi (llass, Diiihlaiil h- in ('Inn itrter 

 Specimen 77(510. Two-thirds natural size 



markings to those which are found on the moldavites of Bohemia, which 

 have lieen described in great detail l)y F. E. Sness,^* who considers them 

 to he of e.Ktraterrestrial origin. 



In the present case the origin of the etch (igiircs is clearly shown by 

 the records contained in the present suite of specimens. The following 

 facts have a direct bearing on the problem: (T ) The etching is evidently 

 the work of hot and iirobablv alkaline solutions. This is inferred from 



13 I 'roc. r. S. National Miisciini. vol. t(i. r.Ml. |.. \Sn. 



".Jahrlj. (1. K. K. <T€oIogiscben Ilcichsanstaii, vol. ">(». I'miii. pii. i'.»:;-;{82. 



