45 
of the diamond, with oxygen or the acidifying principle, proceeds 
carbonate of lime. From this substance, according to its different 
degrees of purity, and modes of combination, is formed chalk ; a sub- 
stance which requires no description — 2\fa, a light porous calca- 
reous substance, chiefly deposited from water, in which carbonate of 
lime had been diffused — Limestones, of various colours and texture, 
employed for paving, and for various purposes of architecture — 
Marbles, which are finer kinds of lime-stones, possessing a closer 
texture, and being capable of assuming a good polish — Calcareous 
spar, named according to the form of its crystals, lenticular spar, 
dog-tooth spar, &c. — Alabaster, formed by the deposition of calca- 
reous matter in clefts of rocks, from the water in which it was sus- 
pended — Stalactites, formed on the roofs of subterranean cavities 
by the gradual accretion of similar matter, from water filtrating 
through the more porous lime-stone ; and Stalagmites, formed by 
the deposition of the same matters on the floors of caverns. 
By. the mixture of lime with clay, are formed the various marls ; 
existing, sometimes, in a soft and pulverescent state, and at other 
times, possessing the hardness of stones. 
By the union of sulphuric acid with lime, is formed gypsum or 
selenite, a substance generally of a white colour, and exhibiting a 
slight degree of lustre and transparency. By intense heat, the lime 
IS obtained from this substance, in a state of considerable purity ; 
and is then termed plaster of Paris. When combined with the acid, 
termed fluoric acid, the substance called Jluor spar is formed, which 
IS so well known to you, by the more common name of Derbyshire 
spar. 
W’ith the phosphoric acid, an acid originating, perhaps, in the 
animal kingdom, lime also frequently combines, to form phosphate 
of lime. By this combination, is also formed phosphorite, a stone 
found in large masses, chiefly in Spain and in Germany* 
