On the Fissure-Inclusions. iii 



near the crossing of two planes. In this, some are completely 

 filled with liquid, many contain bubbles, and in the larger cavi- 

 ties which present projecting prongs, the extremities of the 

 latter seem to be occupied by a second liquid. However, on 

 the examination of several liquid-inclusions in this and 

 other groups, by heating upon the stage to a temperature 

 above 40° C, they were found to be little affected and to con- 

 sist probably of water. 



The letters, a, b, c, etc., are attached in the figure to those 

 cavities in which the bubble exhibited spontaneous motion, the 

 most rapid in the smaller cavities; in all other cavities the 

 bubble was quiet. The motion of these bubbles was found to be 

 entirely unaffected when the beam of light from the mirror 

 either by daylight or from a lamp, was strained from heat-rays 

 by transmission through an alum-cell. In one instance, and 

 only one, a bubble in rapid spontaneous motion was observed 

 to suddenly stop and remain perfectly quiet, but the cause of 

 the stop (possibly some obstacle projecting from the side of the 

 cavity) could not be determined nor could the operation be 

 confirmed by repetition. The longer and more irregular forms 

 of these cavities presented their greater dimensions generally in 

 the plane of the group. 



The remaining constituents of the rock consist of a plagio- 

 clase-feldspar, in rather rare and small striated grains; light- 

 brown hornblende, in straight blades with fine cleavages, but 

 irregularly-rounded terminations, which pass through lighter 

 shades of color, into the next mineral ; fibrolite, occurring not 

 only in the colorless needles but in blades and in beautiful 

 wisps, knots, and bundles of parallel fibers, often macroscopic, 

 seamed with cross-fractures. Under a higher power (X500) 

 the delicate needles are also found to be sharply defined blades 

 of the same form, with pointed terminations, which, however, 

 ^re often rounded, or end abruptly in a transverse fracture, 

 penetrating the quartz mostly in parallel bundles, byt with 

 many lying obliquely in a very irregular mesh. Many are also 

 dislocated into a series of joints, nearly in position, like those 

 so frequently seen in quartz-enveloped crystals of tourmaline 

 or beryl; and there are also a large number of angular frag- 

 ments and scales. 



The accessory minerals observed are the greenish-brown 

 biotite, whose transverse sections are striated and brownish- 



