Davis.] 496 i [February 18, 
spheroidal shape. This seems a possible explanation of these 
inclusions, although further investigations need to be made to test the 
validity of that supposition. 
BANDED AMYGDULES OF THE BRIGHTON AMYGDALOID. 
By Wn. M. Davis. 
In the Spring of 1877, I first noticed a peculiar structure of the 
minerals filling the cavities in the amygdaloid rocks of Brighton, 
which seems to be of value as evidence in regard to their past his- 
tory, and of interest as not occurring in any other amygdaloids so 
far as Ihave learned. While most of the amygdules have a more 
or less distinctly concentric structure, some among them have an 
arrangement of colors in parallel bands, dipping rather uniformly 
about 30°, north; these bands are generally of darker and paler 
reddish jasper, sometimes occupying all the amygdule, sometimes 
only the lower part.when the structure above is uniform or occasion- 
ally concentric. The parallel arrangement of these bands seems to 
indicate a settling to a level, under the influence of gravity; in other 
words a stratification in parallel planes which at the time of forming — 
must have been horizontal. There are some exceptions to the reg- 
ularity of dip of the bands, but the greater number of those I have 
seen are parallel to each other, and some apparent deviations are 
due to the amygdules being exposed by a fracture not on the line of 
dip. They may generally be found in place in a quarry on the west 
side of Allston St., half way between N. Beacon and Warren Sts., 
and have been occasionally seen élsewhere in Brighton. * 
The amygdaloid masses occur between slates and sandstones, which 
dip 30° a little west of north, so that their strata and the planes of 
the banded amygdules are closely parallel. Since the bands of the 
amygdules as well as the strata of the sedimentary rocks must 
have been horizontal when forming, it must be inferred that the 
amygdaloid was forced into its position between the stratified 
rocks above and below, before they were uplifted to their present 
northern dip. This points to a very remote date for the intrusion of 
these eruptive rocks, as the enclosing sandy slates were probably 
tilted early in palaeozoic times. A small piece of evidence of 
another kind is at hand to confirm this conclusion. 
