356 POPULAR SCIENCE MONTHLY. 



them is usually marked by a sort of thread, either continuous or 

 discontinuous, which sometimes suggests a cylindrical cavity, but 

 is more usually in the condition of scattered granulations. The 

 nature of these included bodies can often be determined with pre- 

 cision ; and to select one of the clearest cases, they may not in- 

 frequently be perceived acting energetically upon polarized light 

 as if they were true crystals, while they show geometrical forms 

 on larger or smaller parts of their contour. On closer examina- 

 tion it is possible to refer them to grains of pyroxene. In some 

 of the filaments the axial inclusions are of a different character ; 

 their perceptibly spherical form and other features identify them 

 with the gaseous bubbles frequently observed in rocks. The 



FIG. 2. PELE'S HAIRS SEEN THROUGH THE Fio. 3. PELE'S HAIRS SEEN THROUGH THE 

 MICROSCOPE. Magnified fifteen diam- MICROSCOPE. Magnified one hundred 



eters. diameters. 



matter which fills the cylindrical cavity, often as long as the fila- 

 ments themselves, is also gaseous ; and so likewise are the bubbles 

 that may sometimes be seen by thousands in the vitreous scales, 

 such as are abundantly represented in an angular plate near the 

 edge of Fig. 2. Another point to be noticed is the way the fila- 

 ments terminate that we are sure have not been broken after con- 

 solidation. They are very rarely drawn out to a fine point with- 

 out bending, but usually they suffer a more or less abrupt curve 

 or are done up into a knot or a loop, of which Fig. 3 indicates 

 some common forms. 



If we lightly shake these locks above a sheet of white paper, a 

 fine dust will fall upon it in which the microscope detects among 

 the finest filaments myriads of brownish, translucent, and some- 

 times transparent, vitreous pellets. Most frequently they are per- 

 fectly homogeneous, but they also often contain inclusions similar 

 to those in the filaments. The perfection of their spherical form 

 is not strictly in proportion to their diameter, as might be sup- 



