triple Sulphuret, of Lead, Antimony, and Copper, &c. gg 
are always capable of being referred to the same primitive 
form. This kind of attraction, to exert the full action of which 
it is capable, requires (as well as the attraction of composition) 
that the molecules on which it acts should be situated in a fluid, 
in order that those molecules may possess a perfect freedom of 
motion. It is also necessary that this fluid be at rest ; any mo- 
tion foreign to that of the molecules themselves, disturbs them, 
and necessarily proves an obstacle to that regularity of form 
which is the natural result of their exact union. The fluid must, 
at the same time, be in a situation where it can evaporate gently ; 
which evaporation, causing the molecules slowly to approach 
each other, brings them successively within their sphere of at- 
traction. A crystalline mass may however show no regular 
determinate form, and nevertheless be the result of a regular 
crystallization. Such, for instance, is the formation of the pure 
transparent massive carbonate of lime, known by the name of 
calcareous Alabaster, which exactly fills the fissures or cavities 
in which it is found ; such also is the formation of those sta- 
lactites which are composed of this kind of alabaster. In this 
case, as the cavities are completely filled, there cannot be formed 
in them any distinct crystal ; and the above-mentioned masses 
may be considered as a large aggregation of crystals, the sides 
of which, being similar in form, and situated in the same direc- 
tion, adhere together in one indeterminate mass. But, when that 
happens, the fracture of the mass always shows, in a satisfactory 
manner, the nature of its formation. In the substances I have 
just spoken of, for instance, the fractures are always lamellated ; 
and, by following the direction of the lamellae, we may always 
bring any fragment of the mass into the form of its primitive 
crystal. 
