2 Field Museum of Natural History — Geology, Vol. V. 



gives the chrysolite masses their opaque appearance. As grains of the 

 chrysolite are readily attracted by the magnet, it is probable that this 

 substance is magnetite. On etching the metallic portions of the meteorite 

 the three alloys of the trias are seen to be present with kamacite largely 

 predominating. The alloys are irregularly distributed but in general 

 kamacite in bands 1-3 mm. wide is found bordering the chrysolite. Be- 

 tween the kamacite bands in the metallic portion a narrow dark-gray 

 field of plessite usually occurs, separated from the kamacite on all sides 

 by a thin ribbon of taenite. The outline of the fields of plessite does 

 not follow the direction of the adjoining edge between the chrysolite 

 and kamacite. It is usually broadly sinuous. In other portions of the 

 metallic areas a different arrangement of the trias occurs. Broad, ir- 

 regularly shaped kamacite bands separated by narrow fields of plessite 

 run more or less at right angles to the direction of the chrysolite border. 

 The bands have swollen, rounded outlines and tend to subdivide into 

 twos and threes. Well-marked ribbons of taenite surround the bands 

 and their subdivisions. Figures of this character may be noted near the 

 lower left-hand corner of the section shown in Plate I, Fig. 2. Of 

 accessory minerals there is little evidence. A silver- white, rough, 

 metallic mineral which is probably schreibersite occasionally cuts across 

 the nickel-iron and chrysolite without affecting the structure of either. 

 It also occasionally occurs as a thin layer between the nickel-iron and 

 chrysolite. The specific gravity of a section of the meteorite weighing 

 65 grams was found to be 4.76. This indicates that the nickel-iron and 

 chrysolite are in about equal proportions by weight. 



ARISPE 



In 1902 Ward* described an individual of this fall having a weight of 

 something over 40 kilograms, the exact weight not being stated. This 

 seems to have been the only individual of the fall known at that time, 

 but the writer has since learned through Mr. Edward E. Noon, a min- 

 ing engineer of Sonora, Mexico, of two more masses which evidently 

 belonged to this fall. One of these weighing 62 kilograms (116 lbs.) is 

 now in the collection of the United States National Museum, the other 

 weighing 9 kilograms (20 lbs.) came into the collection of this Museum 

 through the kindness of the late Prof. W. P. Blake. (Mus. No. Me 781). 

 Mr. Noon, who procured both these additional masses, informs the writer 

 that they were found in 1896 about 25 miles northwest of Arispe. Ward 

 gives the locality of the individual which he described as about 1 5 miles 

 northwest of Arispe and the date of find as 1898. The proximity of the 



* Proc. Rochester Acad. Sci. 4, 82-86. 



