13. Riveting hammers; two small tilt hammers for firmly riveting the coaks after they are put into their places.

14. The centre holes through the coaks are next broached out to a true cylinder by means of the broaching engine.

15. The faces of the sheaves are lastly turned to a flat surface in a facing lathe, which also forms the groove in their periphery for receiving the rope. This completes the machine for making the sheaves. The iron pin or axis of the block is forged by two smiths between two swages, or tools each having a semicircular cavity in it, so that the two when put together form a cylinder. The heated iron being laid in one of these, the iron is put over it and beaten with a hammer into a cylindrical form. One end of the pin is left square for a short length. In this state the pins are turned by a slide rest in the pin-turning lathe; this covers them with spiral scratches from the scorings of the tool, and they are afterwards polished and made perfect in the polishing engine, in which the pin is fixed in the lower end of a vertical revolving axis, and forced down into a sort of die immersed in oil holding three pieces of hard steel, between which the pin is pressed as it turns, and this perfects the polish. | Blocks, from 4 to 7 inches in length, are generally fitted with wooden pins, which are turned in a lathe called a whisket.

There are also two machines for making dead-eyes from 5 to 9 inches, and also from 10 to 19 inches in diameter.

There is also a large boring machine, for making the largest sizes of blocks, called made blocks, some of which are as much as 4 feet in length, with four sheaves.

The number of machines employed in making the blocks is forty-four. These are divided into three sets, so that three sets of blocks of different sizes may be proceeding in all their stages at the same time, although in some of these stages one machine operates at the same time upon two, or even ten blocks.

The different blocks made by these machines are as follows:

Thick blocks, four varieties-single sheaves, double sheaves, treble, and fourfold. The sizes of each variety are from 4 inches to 28 inches in length; but only the first three varieties are made wholly by the machine, the fourfold being chiefly made by hand; but their sheaves and pins are entirely formed by the machines.

The number of block-shells, of different sizes, made by each set of machines in a day, is thus stated :

The first set of machines makes blocks, from 4 to 7 inches in length, at the rate of 700 per day. These have wooden pins.

The second set makes blocks, from 8 to 10 inches in length, with iron pins, at the rate of 520 per day. The third set makes blocks, from 11 to 18 inches in length, with iron pins, at the rate of 200 per day. Total, 1,420 per day.

BLOOD is the general circulating fluid of the animal body, the source of nutriment and growth, and the material from which all the secretions are derived. In all vertebrated animals it is of two kinds, the arterial, which is of a bright red colour, and the venous, which is blackish purple. The temperature of the blood is connected with the degree of activity of the respiratory process. In man this temperature is about 98°. The density of blood varies from 1.053 to 1.057. It has a slimy feel, an alkaline reaction, and when recent, a peculiar odour. By the addition of sulphuric acid to old blood, an odour is developed, which is said to be characteristic of the animal from which it was obtained. Soon after blood has been drawn from its vessels, it gelatinizes or coagulates, and the jelly or coagulum separates into two parts, a liquid serum, and a soft clot or crassamentum. During coagulation, the colouring matter, called hematosine, which is diffused through the crassamentum, so as to give it a uniform red colour, is thrown off. This red pigment has many of the characters of a dye stuff, and contains oxide of iron.

The scrum, or fluid part of blood, is an alkaline solution of albumen, containing various soluble salts. The clot is a mechanical mixture of fibrine and colouring matter, swollen and distended with serum. Blood is sometimes used in the arts for the sake of its albumen [See ALBUMEN]: but its use is much less at present than formerly. The chief use of blood is as a manure. It is seldom applied directly to the land, but is made up into a compost by mixing about 50 gallons of blood with a quarter of peat ashes and charcoal powder, and allowing the mixture to stand for a year or two. On light soils this compost raises excellent turnips, when applied alone at the rate of 48 bushels per imperial acre; or of 2 quarters, with 12 tons of farm-yard dung. As a top dressing to young wheat, 20 or 30 bushels an acre greatly increase the crop. In Northamptonshire, where this manure is much used, the blood is contracted for at the rate of 3d. a gallon. In some countries the blood is dried, and applied in the state of powder as a top dressing to the growing crops. In this state it is sold in Paris at about 8s. a cwt.1

BLOWPIPE, an instrument for directing a small jet of air laterally into the flame of a candle or lamp, whereby a portion of the flame is formed into a long slender cone in the direction of the jet, the heat of which increases towards the end of the cone, and at the point is most intense. In this way a common flame is converted into a species of furnace, capable (1)" Johnston's Elements of Agricultural Chemistry:" 1848.

patent for a life-boat with projecting gunwales and hollow cases or double sides under them, as well as air-tight lockers or inclosures under the thwarts or seats for the rowers. These arrangements greatly increased the buoyancy, and prevented rolling. The great defect of this boat was its liability to be staved in. This led to the invention of a life-boat by Mr. Greathead of South Shields, in 1789, which was so successful in its operation, that before the year 1804, it had saved nearly 300 lives from vessels wrecked near the mouth of the Tynemouth haven. The inventor received a gold medal and fifty guineas from the Society of Arts, and a parliamentary reward of 1,2007., besides rewards from the Trinity House and Lloyd's Coffee-house. The success of this boat led to the establishment of stations at most of our ports, where life-boats, manned by active persons, were always kept ready to put to sea for the relief of seamen in distress. This boat, Fig. 164, was 30 feet

Fig. 164. GREATHEAD'S LIFE-BOAT.

in length and 10 feet in breadth, its greatest depth being about 3 feet, besides a general convexity which nearly doubled the depth as reckoned from the ends; the convexity below being intended to give it a greater facility of turning and a greater power of mounting on the waves without submersion of the bow, which would increase the resistance although it would not sink the boat: the breadth was also continued further than usual fore and aft, in order to contribute to the same effect. The gunwale projected some inches, and the sides were cased and lined with cork secured by plates of copper and fastened with copper nails, which gave the boat so much buoyancy that it would float and be serviceable, although so much damaged as to be almost in pieces; but the cork by its softness and elasticity was well calculated to prevent such an accident. The whole quantity of cork was 7 cwt.: on the outside it was 4 inches thick, and extended the whole length of the shear or side of the boat: on the inside it was thicker. Ten short oars of fir were fixed on pins to the gunwales, and a longer oar for steering was fixed at each end, both ends of the boat being alike. The boat was painted white in order to be more conspicuous, and it was entrusted

to an experienced man acquainted with the times and direction of tides and currents, and he was recommended to keep the boat with her head to the waves as much as possible, giving her an increased motion as he neared a wave. Much care is required on approaching the ship in distress, in consequence of the reflux of the waves, and it is in general better to get to the ship on the lee side. The rowers were recommended to exercise themselves in the use of this boat, and to obey strictly the person commanding. A carriage moving on four small wheels was provided for conveying this boat over land when required, but as this plan was not found very convenient, the following was adopted :-Two wheels 9 feet in diameter are connected by an arched axle, to which is fixed a strong pole of considerable length to serve as a lever: the wheels are so far apart that the boat can stand between them with the arched axle over its centre. When the pole is horizontal, the arch rises above the boat, but when the pole is erected perpendicularly, the arch touches the boat. In order to move the boat, the arched axle is brought over its centre and the pole set upright: two chains fastened to the arch are then hooked on to two eyebolts fixed in the inside of the boat: the pole is then lowered, the arch rises and brings up the boat with it. In this way it can be moved rapidly on land, and can be launched with great facility.

In the year 1807, the gold medal of the Society of Arts was awarded to Mr. Christopher Wilson for a life-boat with air gunwales, which is said to be lighter and more manageable than Greathead's boat. One advantage of this boat was that the hollow outriggers or air vessels were distinct from each other, so that if one of them were beaten in by striking on a rock, the rest would still be serviceable.

Since the extensive application of India rubber, and more recently of gutta percha, to the purposes of the useful arts, these substances have been employed with much success in the construction of life boats. Ships have also been furnished with various kinds of life buoys. [See BUOY.] Cork mattrasses have also been partially introduced on board ship, but as they afford facilities to the sailors to desert, they have been discontinued.

BOBBIN-NET. [See LACE.]
BOILER. [See STEAM-ENGINE.]
BOILING. [See EBULLITION.]

BOLE. An earthy mineral forming one of the hydrous silicates of alumina, and resembling Soapstone. Specific gravity, 1.4 to 2. It occurs in masses in Armenia, Saxony, Italy, France, Ireland, Scotland, various parts of South America, &c. It is friable, has a greasy feel, and is of various colours, as yellow, brown, red, and black. When put into water it readily absorbs it, emitting bubbles of air, and falling to pieces. Bole found in the island of Lemnos, is called Lemnian earth, and was formerly employed as an astringent, absorbent, and tonic medicine, but this and the other varieties of bole have fallen into merited neglect as medicines. Any tonic effect they might have had was due to oxide of iron, which is

BOMBAZINE (from the Greek Bóμßuέ, a silkworm). A fabric of worsted and silk, the warp being of silk, and the weft or shoot of worsted.

BONE is formed of a dense cellular tissue of membranous matter, rendered stiff and rigid by insoluble earthy salts, of which phosphate of lime is the most abundant. The proportions of earthy and animal matter vary greatly with the kind of bone, and with the age of the individual, the bones of an adult been richer in earthy salts than those of an infant. The following comparative analysis of human and ox-bones will show the nature and amount of the constituents:

The teeth have a similar composition, but contain less animal matter, so that their texture is more solid and compact than bones. The enamel does not contain more than 2 or 3 per cent. of animal matter. If bone be digested in very dilute muriatic acid, a moderate degree of effervescence will take place in consequence of the presence of carbonate of lime. In some days all effervescence and chemical action will cease, and that which remains undissolved will still represent the size and form of the original bone, but its appearance is changed, for it is semitransparent, cellular, soft, flexible, and to a certain extent elastic. If this be washed and boiled in water, a portion of it will dissolve, and the solution, boiled down to the proper consistence, will become viscid and gelatinous on cooling, and will dry into a hard glue. If again dissolved in water it will become curdy, and give a grey precipitate with solution of nutgalls, and exhibit all the properties of gelatine. The remaining portion is insoluble in water; it becomes hard and somewhat brittle in drying, and burns like horn. Dissolved in caustic fixed alkali, it forms a soapy liquor, and exhibits all the other properties of albumen or membrane. The acid solution in which the bone was steeped will on the addition of caustic ammonia give an abundant precipitate of phosphate of

Fat, although usually present in bone, is not an essential part thereof. The horn of the stag and of other animals of the same kind is entirely free from fat; hence, hartshorn jelly, made by boiling the shavings of stags'-horn in water, is often recommended to persons of very weak digestion in preference to other animal jellies, as being absolutely free from oil; for although hard fat will not combine with jelly, yet the softer oily fats will do so in small proportions.

The

All animals that eat flesh, also eat bones if of a size to be easily crushed and masticated. richness of meat soups is increased by boiling the bones with the meat, but in this way only a small portion of the food contained in bones is made available; a part of the gelatine is with difficulty, and the membranous part not at all, soluble in common boiling water. Much of the fat locked up in the cells of the bone cannot escape unless the cells be broken into. The solid part of the long bones contains, however, very little soluble matter; but their enlarged extremities and articulating surfaces afford the chief supply of nutritive matter. These parts should be sawed off, and the rest broken to pieces. The bones of young animals thus treated will in the course of two or three hours yield most of their soluble matter to boiling water; but in the bones of the older animals the gelatine seems to be in a state of condensation approaching that in which it exists in the skin, and therefore requires the long-continued action of boiling water to separate it. By means of a digester, or boiler with a steam-tight cover and safety valve, the temperature of the water may be safely raised to 270° or 280°, but at a less heat than this the condensed gelatine and membranous portion of the bone become dissolved if previously reduced to small pieces. The insoluble residue will be found a friable, crumbling mass, with scarcely any remains of animal matter. Bone soups are prepared in this way at the hospitals and military head-quarters in France, and it has been proposed to make a collection of dry bones a part of the provisions of a garrison in case of sicge. If formed into stacks covered with thatch, they would be imperishable, and not be exposed to the attacks of mice and rats. The only objection to bone soup is that it sometimes has a burnt flavour, but it has been proposed to get rid of this by first digesting the bones in dilute muriatic acid in a stone trough until the earthy matter is dissolved out; then wash the membranous portion now left in an abundance of water; and lastly, sprinkle it with a little soda to get rid of all traces of the acid. By exposure to the air the membranes will dry to a horny texture without any fear of decomposition; and this can be more easily converted into a palatable food than by cooking the entire bone.

In Norway and Sweden, in times of scarcity, fishbones, such as those of the mackerel, browned on a gridiron until they become friable, and, eaten with pepper and salt, form a palatable food.