4 H. HENSOLDT ON FLUID CAVITIES IN METEORITES. 



opaque ; the other colourless, crystalline, and transparent. 

 The transparent material did not present itself in the form of 

 definitely shaped crystals, but of a multitude of patches, exhibiting 

 every variety of shape and irregularity. In point of relative 

 quantity the two components seemed to be very evenly balanced, 

 the transparent material occurring with the same frequency and 

 bulk as the opaque, although in putting it precisely, I should feel 

 inclined to say that the crystalline matter appeared to indicate 

 a slight preponderance over the amorphous. The whole section, 

 indeed, resembles a network of dark, opaque matter, in which the 

 transparent masses are imbedded. 



Although, as already stated, the transparent patches do not 

 exhibit distinct crystallic outlines, it is by no means difficult to 

 infer from their general appearance that they once possessed dis- 

 tinct crystallic forms ; that they are, indeed, the fragments of 

 crystals, which have, through the agency of violent forces, crush- 

 ing, or sudden heating, been shattered and dislocated from their 

 original positions. 



But another feature is exhibited by these transparent masses, 

 and one which is not so easily perceptible as the points to which I 

 have already drawn attention. On examination with a 2in. objective, 

 we already see scattered over the crystallic fragments, as I may 

 call them, numerous fine points or dots, which in many instances 

 occur in such considerable quantities as to form cloudy congrega- 

 tions, impairing to a slight degree the otherwise very perfect 

 transparency of the crystalline matter. 



It is to these fine dots that we shall now have to direct our chief 

 attention, as the phenomena which they present, and the problems 

 which they suggest, form the essence of this paper. 



On mere superficial examination, those a little versed in micro- 

 scopic petrology would consider these cloudy congregations of fine 

 points to be microlites or crystallites ; those minute bodies which 

 are, as modern research has established beyond any doubt, the true 

 elements of which the crystals are built up. They are present 

 when crystallic forces are about to begin operation, and are 

 likewise originated when crystals are undergoing a disintegrating 

 process, as examples of numerous rock sections show us. 



As we, however, increase the magnifying power of the microscope, 

 these fine dots gradually enlarge, until each ultimately expands 

 into a well-defined cell or cavity, which, according to its size, con- 



