1 14 THE A ME RICA N MUSE UM JO URN A L 



identified as " piezographs " are most conspicuous in a border zone 

 eighteen or twenty inches wide which extends entirely around 

 the rear of the mass. They are from one to three inches in diameter, 

 with a depth approximately one-eighth as great. True piezographs, 

 however, are surface features and are assigned to the heating 

 and attrition due to the action of the greatly condensed air 

 upon a meteorite and particularly upon the front, or brustseite, 

 during its flight through the earth's atmosphere. Three con- 

 siderations show that the small shallow depressions referred to 

 upon Willamette are not piezographs: they are more abundant 

 upon the rear than upon the front of the mass; they cover the 

 inner surface of the great decomposition cavities in the rear, 

 where they could not possibly have been caused by the friction of 

 the atmosphere, as well as the exterior of the mass; the present 

 exterior surface of the meteorite cannot be considered the original 

 surface at the time of fall, and it maybe far removed therefrom. 

 Many pounds of rust and scale were left in the ground when 

 Willamette was lifted out of its first earthly resting place, and 

 it is not probable that the present surface bears any trace of the 

 minor characteristics of the original surface. These slight de- 

 pressions therefore are to be regarded as one of the features 

 of the great iron which are due to unequal oxidation. 



The internal character of the mass has been studied on an 

 etched section in the Ward-Coonley Meteorite Collection on 

 deposit in the Museum and on broken surfaces of the meteorite 

 itself. The fracture shows the iron to be remarkable for its 

 coarsely granular texture, the grains being bounded by almost 

 definite planes suggesting crystals. The etched surface shows 

 that Willamette is to be placed among the Broad Octahedrites 

 (Og), No. 56 of Brezina's system of classification. In this class 

 the lamellae composing the iron are from 1.5 to 2 mm thick. 

 The lamellar structure is somewhat obscured by plates, or flakes, 

 of brighter and more lustrous iron. Most of these areas seem to 

 have no definite outline, but the presence of Neumann lines on the 

 larger ones indicates a crystalline character for them different 

 from that of the main mass as indicated by the lamellae (Ward). 

 The pronounced lamellae are the purer iron and are called kama- 

 cite, the definite lines bounding the kamacite plates are rich in 



