14 



bi- sulphide of carbon evaporates. Minute fluid spheres of a deeper colour 

 than the general mass of the liquid arise in the medium, and grow by mutual 

 absorption. They finally consolidate as clear, transparent isotropic bodies 

 which Vogelsang has termed globulites. Fig. l. (1) It is impossible to ascertain 

 the composition of these bodies with absolute certainty on account of their 

 minuteness ; but there seems no reason to doubt the conclusion of Vogelsang 

 that they are portions of the Canada balsam which are richer in sulphur than 

 the surrounding substance. They evidently arise in consequence of the 

 attempt of sulphur to crystallise under unfavourable circumstances. Similar 

 bodies may be observed in many natural and artificial glasses, although the 

 crystallising compounds must be very different in the different cases. 



Under certain circumstances the mass of sulphur and Canada balsam 

 solidifies with the formation of globulites only ; but under other circumstances 

 additional phenomena may be observed. When the resistance offered by the 

 medium is too great to prevent the union of globulites, but not too great to 

 prevent their approach, they become united into more or less definite forms. 

 (Figs. 2 & 3.) A linear grouping gives rise to the form to which Vogelsang 

 gave the name of margarite. A rectangular grouping is not uncommon. A 

 study of the various modes of grouping led Vogelsang to the conclusion that 

 there are, in each sulphur globulite, three directions or axes of principal 

 attraction. The building-up of compound forms, under the influence of these 

 attractions, naturally leaves the surrounding space free from globulites. 



Sometimes the globulites become fused as it were at the points of contact. 

 In this way rod-like bodies, termed longulites, arise. Forms of great beauty 

 and complexity are often produced by the union of globulites, longulites and 

 margarites, in various ways. It must be remembered that all these forms are 

 isotropic. They cannot, therefore, be regarded as ill-formed crystals. The 

 moment a crystal of sulphur appears it may be recognised by its double- 

 refracting properties. 



3. 



MICROLITES, &c. Microlites differ from crystallites in possessing the 

 internal structure of true crystals. They react on polarised light exactly as a 

 crystal does. They are always minute, and their forms are usually more or 

 less imperfect. Almost all the minerals which occur as common constituents 

 of igneous rocks are found occasionally in the condition of microlites. Some 

 of the commonest forms of microlites are represented below : 



M 



Fig. 5. (After Zirkel.) 



(1) Figs. I, 2, 3 and 4 are taken from Vogelsang's "Die Krystalliten." Bonn. 



