22 PROCEEDINGS OP THE ACADEMY OF [1886. 



or sometimes plicated, the folds corresponding to the long axis. 

 Then they resemble a dried butternut, stripped of its epicarp. 

 Several convex scales may be detached from a flat specimen, 

 placed on edge, with a sharp blow of the hammer. 



Tliey are distributed irregularly through the rock-mass. In 

 some portions they are more abundant than in others. Some 

 parts of the Craftsbury beds are composed entirely of nodules, 

 slightl}' cemented by grains of quartz and mica. It appears 

 that there is no law as to their distribution. From this locality 

 to the Canadian line it is stated that these inclusions are very 

 rare, in the beds extending over this area of about forty miles. 

 (C. H. Hitchcock, Geology of Vermont, vol. 2, pp. 564, 721). 



The Internal Structure. But few microscopic sections of these 

 nodules have been prepared. In studying the lithology of New 

 Hampshire, Mr. G. W. Hawes, formerly of the Sheffield Scientific 

 School, made a section of the centre of a nodule, and observed 

 that the biotite is dichroic, that a small portion of muscovite and 

 some quartz are present. No nucleus was apparent, but a con- 

 centric arrangement of the mica scales, which he considered to 

 be the basis of the formation of the inclusion. (Geolog}^ of New 

 Hamp., vol. 3, pt 4, p. 203.) On account of the limited observa- 

 tions of this peculiar formation, I attempted to prepare some 

 sections of the internal structure. Of these, two were through 

 the centre, and parallel to the longitudinal axis. These show 

 that the biotite is in concentric layers, with grains of quartz scat- 

 tered irregularly through it. No feldspar is present. These 

 layers of biotite are made up of flakes or long bands. Along the 

 thin edges they are of a light brown color, while the thicker 

 masses are dark. The flakes are of different sizes respecting 

 length and width. They are arranged very much like the scales 

 on a fish. The biotite constitutes the greater part of the surface. 

 It forms fully four-fifths, and doubtless even more in some cases. 

 The quartz is remarkably translucent and \ery distinctly vitre- 

 ous. During the grinding process, frequent observations with a 

 lens indicated that the quartz increases in abundance towards 

 the centre. 



Several transverse sections parallel to the lateral axis were 

 attempted, but the brittle nature of the biotite prevented success. 

 This, it is thought, may be accomplislied by hardening a specimen 

 in shellac dissolved in alcohol. Sections through other portions 

 of the nodule denote the laminated structure of the biotite. 



