The Arlinf^ton Fron. — WitichelL 
oric crust. This scale is best preserved in the depr^e«giSiton&.' 
The general appearance of the whole piece is that ©I a refuse 
piece of iron from a furnace. 
On polishing a small portion of the upper surface and ap- 
plying dilute nitric acid for a short time, the characteristic 
crystalline structure becomes beautifully expressed. PlatQ 
X. tig. 2, shows an etched surface, enlarged by photography 
two diameters. The rectangular figure in the lower portion of 
the plate, fig. 3, represents a portion, still further enlargecj 
two diameters, taken from the etched surface at the place 
ehown on the photograph. 
Throughout the etched surface sharp ridges sta^nd up, thu^ 
outlining the coarse Widmanstiittian structure. These eleva- 
tions, represented by the dark lining in both figures of platQ 
X consist of some composition diiferent from the depressions 
^letween them, for they not only resist the acid but they dQ 
not show the bright iron reflections that prevail in the depres- 
sions. These ridges are not entirely persistent and continu- 
ous, but disappear suddenly and rise again. 
Between these long ridges the surface has, after etching, a 
brilliant metallic iron lustre, which is due to the reflection of 
light from crystalline lamellye. These lamellaj are apparently 
cleavages that are in the Widmanstattian bands and they 
stand at different angles in different bands. They- show that 
the bands themselves are crystalline throughout their sub- 
stance. For instance, when placed in the direct sunlight the 
position at which the lamellae marked at a are most illumin- 
ated by reflection is about 45 degrees different from that in 
which the rest of the long lamellae are illuminated". That 
system of coarse lamelhie which is in the lower left hand cor- 
ner of figure 3, in like manner consists of two series. The 
broader upper band reflects light in a position at an angle of 
90°+ from that at which the rest of the associated lamellae 
reflect it. The same fact is observable in other pavta of the 
etched surface. 
These fine lamella?, however, which might be calleii eleav- 
ages, and which characterize the metallic depre^fsions, ar^ 
crossed by a fine striation wholly independent of the long 
Widmanstattian structure. This striation is shewn, in the; 
photograph and in the enlargement. In most ©I these 
