Dr. Walter Flight— History of Meteorites. 75 



If etehed, the beam-iron takes a set lustre, which Haidinger termed 

 crystalline damaskining. Each stripe, when viewed in particular 

 directions, exhibits a sheen, in intervening directions appearing 

 dull ; all stripes have not the same orientation of the lustre, a 

 group, irregularly distributed, always shining forth at the same 

 moment. A single stripe of this form of iron, if only slightly 

 etched, exhibits, under the microscope, very fine etched figures of two 

 kinds : fine threads 0-01 mm. broad, which are straight along one 

 side and serrated on the other; they have the same habit and 

 traverse the same directions as the etched lines that were first 

 observed in the Braunau iron. 1 These threads are the sections of 

 lamellae which are inclosed in definite crystallographic orientation 

 in the beam-iron. When one of them meets a plate of tanite, the 

 former is as a rule terminated, not ^infrequently to be continued in 

 the next stripe of beam-iron ; some, however, which meet a fillet of 

 tiinite at an angle of about 70°, are seen to pass through the last- 

 mentioned mineral. The other appearance, developed by slightly 

 etching the beam-iron, consists of small oblong areas with fine 

 hatching. Seen in favourable light, all the parallel sunken lines 

 shine out along one slope ; and if the plate be rotated through 180°, 

 they light up again along the other ; in intervening positions they 

 appear dull. These brighter areas are often in parallel position, 

 though not invariably so ; if, however, the angles be measured 

 which they make with the fillets of tanite and with the cubic 

 lamella?, it is observed that in point of relative position they exactly 

 accord with the etched lines on the Braunau iron. They never 

 penetrate the plates of tanite. When the corroding action of the 

 acid is prolonged, these appearances are destroyed, and are replaced 

 by etched lines and etched cavities. 



The etehed lines have the same characters as those of the Braunau 

 iron, but they are shorter and more difficult to measure. The section, 

 as stated, is not exactly parallel to the face 811, so that the following 

 determinations of some of the angles which the etched lines make 

 with lines parallel to 100 are only approximate : 



Observed. Calculated for 



100 811 



27° ... ... 26° 34' ... 25° T 



63° 63° 26' ... 64° 7' 



86° 82° 53' ... 85° 40' 



109° ..... ... 104° 2' ... 110° 47' 



119° 119° 45' ... 117° 49' 



while the angles which the etched lines form with lines parallel to 

 111 are : 



Observed. Calculated for 



100 811 



23° 30° 58' ... 23° 51' 



45° 45° 0' ... 45° 24' 



53° 52° 7' ... 48° 58' 



69° 71° 34' ,.. 70° 30' 



These observations place beyond doubt the fact that the deeper 

 lines thus brought out are the usual lines of etching. 



1 J. G. Neumann. Aus der Naturwiss. Abhandl. (TF. Haidinger), iii. Ab. 2, 45. 



