CRYSTALLIZATIONS. 107 



resembles some massive piece of sculpture wrought with elaborate skill. The 

 crystals that compose the arch-like figure are very large in comparison with the 

 rest in this cluster, and yet the distance from a to 6 measures only one- three-hun- 

 dred and fifty -seventh part of an inch. 



VERDIGRIS. The crystals of verdigris are of a fine greenish blue color, and 

 have for their primitive form that of a lozenge or rhomboid. When a drop of 

 the prepared solution is placed upon a slip of glass, it begins to crystallize at 

 the edges, under the action of a mild heat, and clusters of transparent crystals, of 

 the form exhibited at a, in drawing 159, are seen gleaming with a rich blue tint, 

 upon the edge of the drop. Another form like that at b is likewise be- 

 held branching from a single stem, like the leaves of the fleur-de-lis. A 

 similar spicular cluster, in which the stems are more numerous and slender, is 

 observed at c. Another configuration is delineated at d, which originates in a 

 single, diamond-shaped crystal, one point of which, possessing greater energy 

 than the others, has pushed forth a long serrated crystal, from which arrow- 

 headed lateral forms proceed, in a direction parallel to each other. 



The solution of verdigris does not crystallize with rapidity, and as the 

 liquid evaporates slowly in the central portions of the drop, delicate needle- 

 shaped crystals are detected amid the larger forms, crossing each other in all 

 directions. A specimen of this configuration is drawn at e, and throughout the 

 entire surface of the crystallized film, minute crystals of the first form are pro- 

 fusely scattered. The larger crystals of verdigris are extremely well defined, 

 and as perfect as if cut by the lapidary. In the figure d the breadth of one of 

 the lateral crystals at the head ef, is one-five-hundredth of an inch. 



SULPHATE OF MAGNESIA, OR EPSOM SALTS. The crystals of this salt com- 

 bine in figures of exceeding beauty, and with a slow and steady motion. The 

 observer is thus enabled to examine at full leisure the shapeless fluid, as it grad- 

 ually changes into the richest configurations, which grow and expand on every 

 side, lavishly adorned with the most exquisite and singular figures. The crys- 

 tals are best viewed in the evening, by the light of a lamp ; at the moment 

 they begin to form, they are then seen shooting along parallel to each other, in 

 the shape of massive broad shafts, arrow-headed, and serrated on either side, 

 such as are displayed at A in drawing 160. At times their structure is more elabo- 

 rate, and they somewhat resemble long leaves, with strongly marked veins branch- 

 ing from the main stem ; this variety is delineated at B. As the crystals advance, 

 the lateral points or teeth likewise expand in broad crystals, running, some ob- 

 liquely and some at right angles to the principal figure. The lateral crystals 

 likewise throw out from their sides a third set, and thus the ramifications ex- 

 tend until, weaving and interlocking with each other, the entire field of view is 

 covered with the crystalline structure. This in many parts resembles, in the 

 promiscuous grouping of its figures, a surface composed of fern leaves placed 

 upon each other, without any regard to regularity ; but in others the figures are 



