C11 A 1’. Ill*
ON STONE.
701
are formed from the roofs of caverns in the limestone rocks, where the water percolatesthrough them, which is charged with carbonate of lime held in suspension by an excess ofcarbonic acid, which is precipitated by exposure to air.
Limestones are comprised under three denominations, the simple, the oolite, and the mag-nesian ; these are the varieties usually employed in construction : the most crystalline arethe most durable ; some contain a quantity of silica; on many the atmosphere has a power-fully decomposing effect; water being first absorbed acts mechanically on the external facesof the stone, occasioning afterwards, by chemical action, an entire change in the constituentparts.
Of the various limestones examined by the Commissioners appointed by the Governmentpreviously to the erection of the Houses of Parliament, their composition is as follows: —
Barnack.
Chilmark.
Hum Hill.
Silica -
00
10-4
4-7
Carbonate of lime -
93*4
79-0
79 3
--of magnesia -
S*8
3-7
5-2
Iron alumina - - - - -
1-3
2 0
8-3
Water and loss -----
1 -5
4-2
2-5
Bitumen ------
a trace
a trace
a trace
Specific gravities of dry masses -
2090
2-481
2-260
- of particles -
2-627
2-621
2-695
Absorbent powers, when saturated under the ex-
hausted receiver of an air-pump
0-204
0 053
0-147
Disintegration — quantity of matter disintegrated
16 *6 grs.
9-8 grs.
9-5 grs.
j Cohesive powers -----
2 5*
101-
O 1 *
.t
g
4 s
-"Z
Cohesive Powers.
►-J.
*
. .
Name of theQuarry fromwnence Speci-mens wereprocured.
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3 * * 9
a w
Barnack
Ditto
4443-9
4235-4
4442-3
4233-5
4729-4
287-1
0-141
16-6
16
25
Ditto
Chilmark -Ditto
4907-1
4935-9
4*97-0
4925-3
5072-4
174-4
0-080
5-6
36
90
2*182
2-687
0180
Ditto
llam llill -Ditto
4700-3
4685-3
4695-5
4683*5
4930-0
234-5
0*115
9*5
22
57
2*366
•2-G58
0-109
Ditto
2-260
2-695
0-147
Results of experiments upon cubes of 2 inches sides in duplicates.
Results of experimentsupon cubes of 1-inchsides.
Oolite. — This is composed of oviform bodies cemented by calcareous matter of variouscoherency, and is liable to decomposition as the cementing qualities are chemically ormechanically acted upon : that of Bath and Portland is extensively employed in building ;it is worked with great ease, and has a good colour, which it, however, loses when longexposed to the action of the atmosphere; the same cause renders it unfit for fine carving,the delicate portions and arrises soon crumbling away.
The oolites examined by the Commissioners are the following : —
Ancaster.
Bath Box.
Kelton.
Silica -
0 0
o-o
1 -20
2*0
Carbonate of lime -
93-59
94-52
95-16
92*17
-of magnesia
2-90
2*50
1-20
410
Iron alumina ...
0-80
1 -20
0-50
0 90
Water and loss -
2*71
1-78
1-94
2*83
Bitumen -
a trace
a trace
a trace
a trace
Specific gravities of dry masses
2*182
1*839
2-145
2 045
- -of particles -
2*687
2-675
2*702
2-706
Absorbent powers when saturated
under the exhausted receiver of an
air-pump -
0*180
0-312
0*206
0-244
Disintegration — quantity of matter
disintegrated -
7*1
10*
2-7
3-3
Cohesive powers -
33-
21-
SO*
36-