The following Tables give a selection from the results of a great number of experiments upon stone made by various authorities.

In many cases the figures given are not directly comparable with each other, inasmuch as the experiments have been made by different observers and under different conditions.

They afford, however, a useful indication of what may be expected in dealing with stones of different descriptions.

The Table on page 81 shows the weight required to crush stones of different kinds.

Experiments upon the resistance of stones to crushing have generally been made upon cubes.

Professor Eankine says that these experiments indicate "somewhat more than the real strength of the material."

The reason for this is that the fracture of stones under compression generally takes place by their shearing on a plane inclined at a slope having l1/2 rise to 1 of base.

In order to ascertain the strength of any stone for a special purpose, experiments should be made on prisms whose heights are about lú times their diameters.

The hardest stones - such as basalts, primary limestones, slates, etc. - give way suddenly. Other stones begin to crack under from 1/2 to 2/3 the crushing load.

It should be noticed that the size of cubes experimented upon varies considerably. With the same kind of stone the larger the specimen the greater is the weight per square inch required to crush it.

The working stress allowed in practice upon ashlar blocks should not exceed 1/20 of tbe crushing weight given above.2

1 Dent.

2 Stoney On Strains.

Stone.

Crushing

Weight per

Square Inch in Tons.

Length of Side of Cube.

Authority.

Granites.

Inches.

Aberdeen (blue)

4.87

1 1/2

R

Do. .

3.47

1

V

Peterhead .

37

1 1/2

R

Do. .

2.8

1

V

Cornish

2.84

1 1/2

R

Dartmoor .

1.54

l

V

Do.

3.12

Herm

•86

2

B

Mount Sorrel

574

F

Killiney .

4.81

1

W

Ballyknocken .

1.41

1

W

Argyleshire

4.87

. ..

F

Irish (various) .

1.0 to 6.0

1

W

Basalts, etc.

Whinstone

3.69

B

Do. .

5.34

F

Grauwacke, Pen-

7.54

2

F

maenmawr

Felspathic

7.68

W

greenstone

Hornblendic

10.97

.. •

W

greenstone

Irish (various) .

3 1/2 to 14 1/2

1

w

Slates.

Valencia on bed

5

1

W

Do. layers

4.71

1

W

vertical

Glanmore .

9 53

1

W

Killaloe

1371

1

W

Cahircivean

275

1

W

Sandstones.

Bramley Fall .

27

11/2

R

Do. . .

2.5

1

V

Craigleith .

1.4

1

V

Do.

2.45

1 1/2

R

Do. .

3 5

2

C

Dundee

3.-85

1 1/2

R

York paving

2.56

1 1/2

R

Binnie

2.24

2

C

Darley Dale

3.16

2

C

Giffneuk .

2.15

2

C

Kenton

2.21

2

C

Mansfield (red) .

2.27

2

C

Do. (white)

2.34

2

c

Morley Moor

2.21

2

c

Park Spring

3.38

2

c

Stanley

2..66

2

c

Strong Yorkshire,

4.38

2

F

mean of 9 expts.

Irish (various) .

•75 to 10.0

1

w

Stone.

Crushing Weight per Square Inch in Tons.

Length of Side of Cube.

Authority.

Sandstones.

Inches.

Weak specimens, locality not stated

1.34 to 1.56

2

F

Runcorn .

0.97

L. Clark

Quartz rock on natural bed

11.38

Mallet

Quartz rock, layers vertical

6.25

Do.

Marbles.

White statuary .

1.43

1

R

Do.

27

1 1/2

R

Black Brabant .

9.46

1 1/2

R

White Italian .

9.72

1 1/2

R

Devon (red)

3.31

R

Kilkenny (black)

675

1

W

Galway, do.

9

1

W

Limestones.

Compact (strong)

3.8

2

F

Magnesian, do.

3.16

2

F

Do. (weak)

1.36

2

F

Portland .

1.66

2

R

Do.

2.03

1 1/2

R

Do.

1.5

2

I

Do.

1.17

1

V

Do.

1.74

2

C

Purbeck .

4.08

1 1/2

R

Ancaster .

1.04

2

C

Barnack .

0.79

2

c

Ketton

1.14

2

c

Do. (rag)

4.01

2

c

Bath (Box)

0.66

2

c

Do. .

0.54

1

V

Chalk

0.5

1 1/2

R

Bolsover .

3.36

2

c

Bramham Moor

2.64

2

c

Brodsworth

2.05

2

c

Cadeby

0.72

2

c

Chilmark .

2.84

2

c

Hamhill .

1.8

2

c

Huddlestone

1.93

2

c

Park Nook

1.93

2

c

Roche Abbev

1.74

2

c

Do. " .

0.69

1

V

Totternhoe

0.86

2

c

Anston

1.36

F

Anglesea ,

3.33

...

L. Clark

Listowel .

8.33

1

w

Longhome

7.68

1

w

Ballyduff .

4.93

1

w

Moyne

8.03

1

w

Limerick .

3.9

1 1/2

R

Irish (various) .

•5 to 14.0

1

W

I, Institution of British Architects. B, Bramah.

B, Buchanan, quoted by Stoney F, Fairbaim, Useful Information for Engineers.

R Rennie. W. Wilkinson, Practical Geology, Ireland.

C, Commissioners on Stone for Houses of Parliament.