8 
The JYaturalists’ Companion. 
fossils will be obliterated. Crystalliz¬ 
ation is a sign of great age. 
As I said befoie, the ocean holds vast 
amounts of carbonate of lime in solution. 
This is deposited in the same manner as 
salt; by the water evaporating in certain 
jdaces where it has been isolated by 
some change in the form of the earth’s 
surface, leaving a bed of limestone. 
Limestone is not formed in this manner 
at the present time, but we have good 
leason to believe it was formed so ages 
ago. A similar method - is that which 
forms calcareous tufa, which is limestone 
deposited by water ; such as mineral 
springs, geysers and rivers. 
Water leaking into the roof of a cave 
often contains calcitein solution. The 
water evaporites leaving the calcite. In 
time quite an amount of calcite will be 
left in the lorm of an icicle, called a 
stalactite. When more water leaks 
through than can be evaporated, some 
tails to the bottom of the cave, and the 
calcite in it forms an inverted icicle 
called a stalagmite. wSometimes these 
stalactites and stalagmites meet,forming 
pillars. 
The ganular and crystalline varieties 
of limestone are called marble ; but mar¬ 
ble is not a scientific name, and may 
mean any rock that is calcareous and 
takes a polish. The finest and purest 
white marble is used for statuary, d'he 
finest marble comes from Carrara, Italy; 
the Island of Paros, whence the name 
Parain; from Athens, Greece; and from 
Ornofrio, Corsica. Many of the fine 
Greek statues are made from Parian 
marble. The statuary marble found in 
theUnited States is not of a good quality, 
but good building material is abundant. 
The best kinds of building marble are 
not excelled by granite for durability. 
Chalk is a white and earthy variety 
of limestone. This must not be con¬ 
founded with the chalk used to mark on 
a blackboard, which is made from clay. 
Chalk is abundant in Europe, but is not 
found in America. When examined by 
the naked eye, it seems to be destitute 
of organic lemains, but when seen un¬ 
der the microscope, it appears to be a 
mass of shells. Chalk is composed of 
the shells of Foiaminifera. Although 
the chalk which we see now was formed 
ages ago, we have good reason to be¬ 
lieve that chalk is being formed at the 
present time. 'Phere are thousands of 
square miles in the deeper parts of the 
ocean where the dredge brings up little 
more than a gray calcareous slime or 
ooze. When examined with a micro¬ 
scope, it is found to be composed prin¬ 
cipally ot Foraminifera. When this 
ooze is dried and pressed, it forms a 
white rock like chalk; it is, in fa6t, a 
modern chalk. The crystalline varieties 
of limestone are termed spar. Many of 
the crystals are very beautiful. Nail- 
head spar and dog-tooth spar are so 
called because of their resemblance to 
those objects. Iceland spar is a trans¬ 
parent variety. It derives its name by 
its first being found in Iceland. Satin 
spar is a finely fibrous variety with a 
.satin lustre. Marl, which is of great 
value in agriculture, is a mixture of car¬ 
bonate of lime with clay. It often cou- 
tains fossil shells. • 
']'HE END. 
Mr. J. H. Martin, in “Science Gxos- 
sip, says that a good method.for preserv¬ 
ing iungi is to place them in a solution 
of one part calcium chloride (chloride 
of lime) and ten jjarts water. This will 
change the phosphates of the fungus in¬ 
to ])hosphate of lime, after which they 
will be tound to kee}) well. 
