As we have not space for detailing the particulars of each experiment, we here add only the average results of them.

The experiments on cast iron, in cubes of one-eighth of an inch, - specific gravity 7.033, gave 1439 lbs. avoirdupois, as the average force required to crush them.

On specimens of the same iron, one-eighth of an inch square, and one-fourth of an inch long, the average force required was 2116 lbs.

On specimens of the same thickness, but varying in length from one-half of an inch to one inch, the average result was 1758 lbs.

On cubes of a quarter of an inch of the same metal, gave 9773 lbs. as the average result.

On one-fourth of an inch cubes, made from horizontal castings of specific gravity, 7.113 gave 10,114 lbs. as the average.

On one-fourth of an inch cubes, vertical castings, specific gravity 7.074, the average was 11,136 lbs.

A prism, having a logarithmic curve for its limits, resembling a column, (it was one-fourth of an inch diameter, by one inch long,) broke with 6954 lbs.

The trials on prisms, of different lengths, one-fourth and one-half horizontal, gave 9414 lbs.

The same, vertical, gave 9982 lbs.

Horizontal castings, varying from three-eighths to six-eights of an inch X 1/4, gave an average of 8738 lbs.

Vertical ditto, gave 8536 lbs.

Experiments on different Metals.

lbs.

1/4 X 1/4

cast copper, crumbled with fine yellow brass reduced 1/10

. . . . . . . . . . . . . . .. . . . . . .

with 3213 1/3 lbs. with . .

7318

"

10304

"

wrought copper . . . . .. . . . .1/16

. . . 3427 1/3 . . . . . . . . . .

6440

"

cast tin . . . . . .. . . . . . . . . . . . 1/16

. . . 552 1/3 . . . . . . . . . .

966

"

cast lead . . . . .. . . . . . . . . . . .. . . .

. . . . 1/2 . . .. .. . . . .

483

The experiments on the different metals gave no satisfactory results. The difficulty consists in assigning a value to the different degrees of diminution. When compressed beyond a certain thickness, the resistance becomes enormous.

Experiments on the Suspension of Bars.

The lever was used as in the former case, but the metals were held by nippers. They were made of wrought iron, and their ends adapted to receive the bars, which, by being tapered at both extremities, and increasing in diameter from the actual section, and the jaws of the nippers being confined by a hoop, confined both. The bars, which were six inches long, and one quarter square, were thus fairly and firmly grasped

lbs.

1/4

inch cast-iron, horizontal ...................................................

1166

1/4

ditto ditto, vertical ..........................................................

1218

1/4

ditto cast-steel, previously tilted ......................................

8391

1/4

ditto blister steel, reduced per hammer ............................

8322

1/4

ditto shear steel ......... ditto ..............................................

7977

1/4

ditto Swedish iron ..... ditto .............................................

4504

1/4

ditto English iron ...... ditto .............................................

3492

1/4

ditto hard gun-metal, mean of two trials ..........................

2273

1/4

ditto wrought copper, reduced per hammer .....................

2112

1/4

ditto cast copper ...............................................................

1192

1/4

ditto fine yellow brass .....................................................

1123

1/4

ditto cast tin ......................................................................

296

1/4

ditto cast lead ....................................................................

114

Experiments on the Twist of 1/4 inch Bars,

To effect the operation of twisting off a bar, another apparatus was prepared. It consisted of a wrought-iron lever, two feet long, having an arched head about one-sixth of a circle, of four feet diameter, of which the lever represented the radius; the centre, round which it moved, had a square hole made to receive the end of the bar to be twisted. The lever was balanced as before, and a scale hung on the arched head; the other end of the bar being fixed in a square hole in a piece of iron, and that again in a vice. By this apparatus, quarter of an inch bars, from horizontal castings, were twisted with weights in the scale, averaging 9 lbs. 15 oz. The vertical castings took 10 lbs. 10 oz. as an average.

On different Metals.

lbs.

oz.

Cast steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17

9 in the scale

Shear steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17

1

Blister steal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16

11

English iron, wrought . . . . . . . . . . . . . . . . . . . . . .

10

2

Swedish iron, wrought . . . . . . . . . . . . . . . . . . . .

9

8

Hard gun-metal . . . . . . . . . . . . . . . . . . . . . . . . . . .

5

0

Fine yellow brass . . . . . . . . . . . . . . . . . . . . . . . . .

4

11

Copper, cast . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

5

Tin.............. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

7

Lead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

0

On Twists Of Different Lengths

Horizontal.

lbs.

oz.

1/2

by

1/2

long................................................

7

3 weight in scale

1/4

by

3/4

ditto...............................................

8

1

1/4

by

1

inch ditto.........................................

8

8

Vertical.

1/4

by

1/2

ditto.......................................................................

10

1

1/4

by

3/4

ditto.........................................................................

8

9

1/4

by

1

inch ditto..................................................................

8

5

Horizontal twists of quarter of an inch bars, at six inches from the bearing, took an average of 9lbs. 12oz. in the scale.

Twists of 1/2 inch square Bars, cast horizontally.

qrs.

lbs.

oz.

1/2

close to the bearing............................................

1

3

9

J 2 end of the bar hard.

1/2

ditto...................................................................

2

18

0 middle of the bar.

1/2

at 10 inches from bearing, lever in the middle........................................

1

24

0

On Twists of different Materials.

These experiments were made close to the bearing, and the weights were accumulated in the scale, until the substances were wrenched asunder.

lbs.

oz.

Cadt steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

19

9 weight in scale.

Shear steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17

1

Blister steel . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16

11

English iron , No. 1. . . . . . . . . . . . . . . . . . . . . .

10

2

Swedish iron . . . . . . . . . . . . . . . . . . . . . . . . . . .

9

8

Hard gun-metal . . . . . . . . . . . . . . . . . . . . . . . . .

5

0

Fine yellow brass . . . . . . . . . . . . . . . . . . . . .

4

11

Copper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

5

Tin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

7

Lead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

0

Miscellaneous Experiments on the Crush of 1 cubic inch.

lbs. avoir

Elm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . .

1284

American pine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . .

1606

White deal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . .

1928

English oak, mean of two trials . . . . . . . . . . . . . . . . . . . . . . . . . .

3860

Ditto, of five inches long, slipped with . . . . . . . . . . . . . . . . . .

2572

Ditto, of four inches long, slipped with . . . . . . . . . . . . . . . . . .

5147

A prism of Portland stone, two inches long . . . . . . . . . . . . . . . . .

805

Ditto, statuary marble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .

3216

Craig Leith . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .

8688

In the following experiments on stones, the pressure was communicated through a kind of pyramid, the base of which rested on the hide leather, and that on the stone. The lever pressed upon the apex of the pyramid. The cubes were of one and a half inch.

Spec. grav.

lbs. av.

Chalk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . .

1127

Brick, of a pale red colour . . . . . . . . . . . . . . . . . . . . . . . . .

2.085

1265

Roe-stone, Gloucestershire . . . . . . . . . . . . . . . . . . . . . . . . .

1449

Red brick, men of two trials . . . . . . . . . . . . . . . . . . . . . . . . .

2.168

1817

Yellow-faced baked Hammersmith paviours three time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2254

Burnt ditto, means of two trials . . . . . . . . . . . . . . . . . . . . . .

3243

Stoourbridges, or fire brick . . . . . . . . . . . . . . . . . . . . . . . . .

3864

Derby grit, a red friable sandstone . . . . . . . . . . . . . . . . . . .

. 2.316

7076

Ditto, from another quarry . . . . . . . . . . . . . . . . . . . . . . . . .

2.428

9776

Killaly white freestone, not stratified . . . . . . . . . . . . . . . . .

2.423

10264

Portland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.428

10284

Craig Leith, white freestone . . . . . . . . . . . . . . . . . . . . . . . .

2.452

12346

Yorkshire paving, with the strate . . . . . . . . . . . . . . . . . . . .

2.085

12856

Ditto, against the strata . . . . . . . . . . . . . . . . . . . . . . . . .

2.507

12856

Cornish granite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.760

13632

Branley Fall sandstone, near Leeds, with strata .

2.506

13632

Ditto, against the strata . . . . . . . . . . . . . . . . . . . . . . . . .

2.506

13632

Cornish granite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.662

14302

Dundee sandstone or brescia, two kinds . . . . . . . . . . . . . .

2.530

14918

A two-inch cube of Portland . . . . . . . . . . . . . . . . . . . . . . . .

2.423

14918

Craig Lieth, with the strata . . . . . . . . . . . . . . . . . . . . . . . . .

2.452

15560

Devonshire red marble, variegated . . . . . . . . . . . . . . . . . .

16712

Compact limestone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.584

17354

Peterhead granite, hard, close-grained . . . . . . . . . . . . . .

18636

Black compact limestone, Limerick . . . . . . . . . . . . . . . . . . .

2.598

19924

Purbeck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.599

20610

Black Brabant marble . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.697

20742

very hard freestone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.528

21254

White Italian veined marble . . . . . . . . . . . . . . . . . . . . . . . . .

2.726

21783

Aberdeen granite, blue kind . . . . . . . . . . . . . . . . . . . . . . . . .

2.625

24556

N.B

The specific gravities were taken with a delicate balance, made by Creighton, of Glasgow, all, with the exception of two specimens, which were by accident omitted.

Remarks

In observing the results presented by the preceding table, it will be seen that little dependence can be placed on the specific gravities of stones, so far as regards their cohesive powers, although the increase is certainly in favour of their specific gravities. But there would appear to be some undefined law in the connexion of bodies, with which the specific gravity has little to do. Thus, statuary marble has a specific gravity above Aberdeen granite, yet a eohesive power not much above half the latter. Again, hardness is not altogether a characteristic of strength, inasmuch as the limestones, which yield readily to the scratch, have nevertheless a cohesive power approaching to granite itself.

Experiments made on the transverse strain of Cast Bars, the ends loose.

Weight of the bars

Distance of bearings

lbs.

oz.

ft.

in.

lbs. av.

Bar of 1 inch square................................................

12

6

3

0

897

Ditto of 1 inch ditto................................................

9

8

2

8

1086

Half the above bar..................................................

1

4

2320

Bar of 1 inch square through the diagonal.................................................................

2

8

2

8

851

Half the above bar..................................................

1

4

1587

Bar of 2 inches deep, by \ inch thick

9

5

2

8

2185

Half the above bar..................................................

1

4

4508

Bars 3 inches deep, by 1/3 inch thick.......................

9

15

2

8

3588

Half the above bar..................................................

1

4

6854

Bar 4 inches, by 1/4 inch thick ................................

9

7

2

8

3979

Equilateral triangles, with the angles up and down, viz., with the edge or angle up..........................................................

9

11

2

8

1437

With the angle down...............................................

9

7

2

8

840

Half the first bar....................................................

1

4

3059

Half the second bar................................................

1

4

1656

A feather-edged bar was cast, whose dimensions were 2 inches deep by 2 wide, edge up........................................

10

0

2

8

3105

N.B

All these bars contained the same area, though differently distributed as to their forms.

Experiments made on the Bar of 4 inches deep by 1/4 inch thick, by giving it different forms, the bearings at 2 feet 8 inches, as before.

lbs.

Bar formed into a semi-ellipse, weight 7 lbs . . . . . . . . . . . . .

4000

Ditto parabolic on its lower edge . . . . . . . . . . . .. . . . . . . . . . .. .

3860

Ditto of 4 inches deep by 1/4 inch thick . . . . . . . . . . . . . . . . . .

3979

Experiments on the transverse strain of Bars, one end made fast, the weight being suspended at the other, at 2 feet 8 inches from the bear ing.

lbs.

An inch-square bar bore . . . . . . . . . . . .. . . . . . . . . . . . . . . . . .

280

A bar 2 inches deep by 1/2 an inch thick . . . . . . . . . . . . . . . . .

539

An inch bar, the ends made fast . . . . . . . . . . . .. . . . . . . .. . .

1173

The paradoxical experiment of Emerson was tried, which states, that by cutting off a portion of an equilateral triangle, (see page 114 of Emerson's Mechanics,) the bar is stronger than before; that is, a part stronger than the whole. The ends were loose at two feet eight inches apart, as before. The edge from which the part was intercepted was lowermost; the weight was applied on the base above; it broke with 1129 pounds, whereas in the other case it bore only 840 pounds.