148 MM. Godon’s mineralogical observations. 
to beatwelfth. The resuit of the present observations differs from that of 
this celebrated chemist. But if we consider the petrosilex and argil- 
loid as aggregates, we shall not be surprised to find so great a variety 
in the results of the analyses of these minerals, though placed under 
the same title. | 
Wacke. 
33. One of the predominant rocks of the country, and undoubted- 
ly the most remarkable, is that bordering upon Boston in a south di- 
rection, which appears to spread itself from northwest to southeast, and 
oe is observed, in full display, principally in the towns of Brigh- . 
on, Brookline, Roxbury, Milton, and Dorchester, when it disappears 
bi the sea, 
This rock, denoted in the country by the name of plum. pudding 
stone, is formed of conglutinated kernels, of different sizes, colour, 
and nature. The most apparent are, . 
1. Quartz, mostly opaque, compact or granulated, of a great di- 
versity of colours (whitish, blueish, greenish, reddish, of different de- 
grees of intensity), sometimes with the aspect of petrosilex (but with- — 
out fusibility), and presenting, now and then, some small bright crys- 
tals of felspar. 
2. Petrosilex and argilloid, variously coloured (greyish, blueish, 
reddish, 20& 29). | When the fragments of these two are predomi- 
nant, the rock presents the aspect of breccia, sometimes analogous tO 
the diaspro breciato of the Italians, antique breccia. | 
3. Nodules, consisting of grains of whitish, greyish or reddish: 
