Chapter V: Part 5

Openings must always be made in boilers for access for cleaning and examination. When these are large enough to allow a man to enter the boiler they are termed man-holes. They are usually made oval, as this shape permits the doors by which they are closed to be placed on the inside so that the pressure upon them tends to keep them shut. The doors are held in place by one or two bolts, secured to cross-bars or "dogs" outside the boiler. It is important in making these doors that they should fit the holes so accurately that the jointing material cannot be forced out of its proper position. In the few cases where doors are fitted outside a boiler, so that the steam-pressure tends to open them, they are always secured by several bolts so that the breakage of one bolt will not allow the door to be forced off.

_Water-softening._--Seeing that the impurities contained in the feed-water are not evaporated in the steam they become concentrated in the boiler water. Most of them become precipitated in the boiler either in the form of mud or else as scale which forms on the heating surfaces. Some of the mud and such of the impurities as remain soluble may be removed by means of the blow-off cocks, but the scale can only be removed by periodical cleaning. Incrustations on the heating surface not only lessen the efficiency of the boiler by obstructing the transmission of heat through the plates and tubes, but if excessive they become a source of considerable danger by permitting the plates to become overheated and thereby weakened. When the feed-water is very impure, therefore, the boilers used are those which permit of very easy cleaning, such as the Lancashire, Galloway and Cornish types, to the exclusion of multitubular or water-tube boilers in which thorough cleaning is more difficult. In other cases, however, the feed-water is purified by passing it through some type of "softener" before pumping it into the boiler. Most of the impurities in ordinary feed-water are either lime or magnesia salts, which although soluble in cold water are much less so in hot water. In the "softener" measured quantities of feed-water and of some chemical reagents are thoroughly mixed and at the same time the temperature is raised either by exhaust steam or by other means. Most of the impurity is thus precipitated, and some of the remainder is converted into more soluble salts which remain in solution in the boiler until blown out. The water is filtered before being pumped into the boiler. The quantity and kind of chemical employed is determined according to the nature and amount of the impurity in the "hard" feed-water.

_Thermal Storage._--In some cases where the work required is very intermittent, "thermal storage" is employed. Above the boiler a large cylindrical storage vessel is placed, having sufficient capacity to contain enough feed-water to supply the boiler throughout the periods when the maximum output is required. The upper part of this storage vessel is always in free communication with the steam space of the boiler, and from the lower part of it the feed-water may be run into the boiler when required. The feed-water is delivered into the upper part of the vessel, and arrangements are made by which before it falls to the bottom of the chamber it runs over very extended surfaces exposed to the steam, its temperature being thus raised to that of the steam. At times when less than the normal supply of steam is required for the engine more than the average quantity of feed-water is pumped into the chamber, and the excess accumulates with its temperature raised to the evaporation point. When an extra supply of steam is required, the feed-pump is stopped and the boiler is fed with the hot water stored in the chamber. Besides the "storage" effect, it is found that many of the impurities of the feed become deposited in the chamber, where they are comparatively harmless and from which they are readily removable.

Section at AB--Front elevation.

FIG. 17.--Bobcock & Wilcox Water-tube Boiler (marine type).]

_Oil Separators._--When the steam from the engines is condensed and used as feed-water, as is the case with marine boilers, much difficulty is often experienced with the oil which passes over with the steam. Feed-filters are employed to stop the coarser particles of the oil, but some of the oil becomes "emulsified" or suspended in the water in such extremely minute particles that they pass through the finest filtering materials. On the evaporation of the water in the boiler, this oil is left as a thin film upon the heating surfaces, and by preventing the actual contact of water with the plates has been the cause of serious trouble. An attempt has been made to overcome the emulsion difficulty by uniformly mixing with the water a small quantity of solution of lime. On the water being raised in temperature the lime is precipitated, and the minute particles separated apparently attract the small globules of oil and become aggregated in sufficient size to deposit themselves in quiet parts of the boiler, whence they can be occasionally removed either by blowing out or by cleaning. Much, however, still remains to be done before the oil difficulty will be thoroughly removed.

_Corrosion._--When chemicals of any kind are used to soften or purify feed-water it is essential that neither they nor the products they form should have a corrosive effect upon the boiler-plates, &c. Much of the corrosion which occasionally occurs has been traced to the action of the oxygen of the air which enters the boiler in solution in the feed-water, and the best practice now provides for the delivery of the feed into the boiler at such positions that the air evolved from it as it becomes heated passes direct to the steam space without having an opportunity of becoming disengaged upon the under-water surfaces of the boiler.

Where corrosion is feared it is usual to fit zinc slabs in the water spaces of the boiler. Experience shows that it is better to make them of rolled rather than of cast zinc, and to secure them on studs which can be kept bright, so as to ensure a direct metallic contact between the zinc and the boiler-plate. The function of the zinc is to set up galvanic action; it plays the part of the negative metal, and is dissolved while the metal of the shell is kept electro-positive. Care must always be taken that the fragments which break off the zinc as it wastes away cannot fall upon the heating surfaces of the boiler.

_Evaporators._--In marine boilers the waste of water which occurs from leakages in the cycle of the evaporation in the boiler, use in the engine, condensation in the condenser and return to the boiler as feed-water, is made up by fresh water distilled from sea-water in "evaporators." Of these there are many forms with different provisions for cleaning the coils, but they are all identical in principle. They are fed with sea-water, and means are provided for blowing out the brine produced in them when some of the water is evaporated. The heat required for the evaporation is obtained from live steam from the boilers, which is admitted into coils of copper pipe. The water condensed in these coils is returned direct to the feed-water, and the steam evaporated from the sea-water is led either into the low-pressure receiver of the steam-engine or into the condenser.

_Efficiency of Boilers._--The useful work obtained from any boiler depends upon many considerations. For a high efficiency, that is, a large amount of steam produced in proportion to the amount of fuel consumed, different conditions have to be fulfilled from those required where a large output of steam from a given plant is of more importance than economy of fuel. For a high efficiency, completeness of combustion of fuel must be combined with sufficient heating surface to absorb so much of the heat produced as will reduce the temperature of the funnel gases to nearly that of steam. Completeness of combustion can only be obtained by admitting considerably more air to the fire than is theoretically necessary fully to oxidize the combustible portions of the fuel, and by providing sufficient time and opportunity for a thorough mixture of the air and furnace gases to take place before the temperature is lowered to that critical point below which combustion will not take place. It is generally considered that the amount of excess air required is nearly equal to that theoretically necessary; experience, however, tends to show that much less than this is really required if proper means are provided for ensuring an early complete mixture of the gases. Different means are needed to effect this with different kinds of coal, those necessary for properly burning Welsh coal being altogether unsuitable for use with North Country or Scottish coal. As all the excess air has to be raised to the same temperature as that of the really burnt gases, it follows that an excess of air passing through the fire lowers the temperature in the fire and flues, and therefore lessens the heat transmission; and as it leaves the boiler at a high temperature it carries off some of the heat produced. A reduction of the amount of air, therefore, may, by increasing the fire temperature and lessening the chimney waste, actually increase the efficiency even if at the same time it is accompanied by a slight incompleteness of combustion.

_Mechanical Stoking._--Most boilers are hand-fired, a system involving much labour and frequent openings of the furnace doors, whereby large quantities of cold air are admitted above the fires. Many systems of mechanical stoking have been tried, but none has been found free from objections. That most usually employed is known as the "chain-grate" stoker. In this system, which is illustrated in fig. 13 (Woodeson boiler), the grate consists of a wide endless chain formed of short cast-iron bars; this passes over suitable drums at the front and back of the boiler, by the slow rotation of which the grate travels very slowly from front to back. The coal, which is broken small, is fed from a hopper over the whole width of the grate, the thickness of the fire being regulated by a door which can be raised or lowered as desired. Thus the volatile portions of the coal are distilled at the front of the fire, and pass over the incandescent fuel at the back end. The speed of travel is so regulated that by the time the remaining parts of the fuel reach the back end the combustion is nearly complete. It will be seen that the fire becomes thinner towards the back, and too much air is prevented from entering the thin portion by means of vanes actuated from the front of the boiler.

_Draught._--In most boilers the draught necessary for combustion is "natural," i.e. produced by a chimney. For marine purposes, although "natural" draught is the more common, many boiler installations are fitted with "forced" draught arrangements. Two distinct systems are used. In that known as the "closed stokehold" the stokehold compartment of the vessel is so closed that the only exit for air from it is through the fires. Air is driven into the stokehold by means of fans which are made so that they can maintain an air pressure in the stokehold above that of the outside atmosphere. This is the system almost universally adopted in war vessels, and it is used also in some fast passenger ships. The air pressure usually adopted in large vessels is that corresponding to a height of from 1 to 1-1/2 in. of water, whilst so much as 4 in. is sometimes used in torpedo-boats and similar craft. This is, of course, in addition to the chimney-draught due to the height of the funnel. In the closed ashpit or Howden system, the stokehold is open, and fans drive the air round a number of tubes, situated in the uptake, through which the products of combustion pass on their way to the chimney. The air thus becomes heated, and part of it is then delivered into the ashpit below the fire and part into a casing round the furnace front from which it enters the furnace above the fire. In locomotive boilers the draught is produced by the blast or the exhaust steam. With natural draught a combustion of about 15 to 20 lb. of coal per sq. ft. of grate area per hour can be obtained. With forced draught much greater rates can be maintained, ranging from 20 lb. to 35 lb. in the larger vessels with a moderate air pressure, to as much as 70 and even 80 lb per sq. ft. in the express types of boiler used in torpedo boats and similar craft.

_Performance of Boilers._--The makers of several types of boilers have published particulars regarding the efficiency of the boilers they construct, but naturally these results have been obtained under the most favourable circumstances which may not always represent the conditions of ordinary working. The following table of actual results of marine boiler trials, made at the instance of the British admiralty, is particularly useful because the trials were made with great care under working conditions, the whole of the coal being weighed and the feed-water measured throughout the trials by skilled observers. The various trials can be compared amongst themselves as South Welsh coal of excellent quality was used in all cases.

In experimental tests such as those above referred to, many conditions have to be taken into account, the principal being the duration of the trial. It is essential that the condition of the boiler at the conclusion of the test should be precisely the same as at the commencement, both as regards the quantity of unconsumed coals on the fire-grate and the quantity of water and the steam-pressure in the boiler. The longer the period over which the observations are taken the less is the influence of errors in the estimation of these particulars. Further, in order properly to represent working conditions, the rate of combustion of the fuel throughout the trial must be the same as that intended to be used in ordinary working, and the duration of the test must be sufficient to include proportionately as much cleaning of fires as would occur under the normal working conditions. The tests should always be made with the kind of coal intended to be generally used, and the records should include a test of the calorific value of a sample of the fuel carefully selected so as fairly to represent the bulk of the coal used during the trial. The periodic records taken are the weights of the fuel used and of the ashes, &c., produced, the temperature and quantity of the feed-water, the steam pressure maintained, and the wetness of the steam produced. This last should be ascertained from samples taken from the steam pipe at a position where the full pressure is maintained. In order to reduce to a common standard observations taken under different conditions of feed temperatures and steam pressures, the results are calculated to an equivalent evaporation at the atmospheric pressure from a feed temperature of 212 deg. F. (J. T. Mi.)

TRIALS OF VARIOUS TYPES OF MARINE BOILERS

+----------------------------+-------+--------+--------+-----------+---------+---------+----------------+----------+---------+------+
| | | | | | Air | |Water Evaporated| Water | | |
| | | | | Coal |Pressure |Chimney |per lb. of Coal.| Evapor- | Thermal |Effic-|
| | Grate |Heating |Duration| burned |in Stoke-|Draught--+-------+--------+ated per |Units per|iency |
| Description of Boiler. | Area |Surface |of Trial|Per sq. ft.| hold-- |Inches of| |From and|sq. ft. of| lb. of | of |
| |sq. ft.|sq. ft. | Hours. | of Grate |Inches of| Water |Actual | at 212 | Heating | coal. |Boiler|
| | | | | per Hour. | Water. | | | deg. F.| Surface. | | %. |
+----------------------------+-------+--------+--------+-----------+---------+---------+-------+--------+----------+---------+------+
|Ordinary cylindrical single-| 81 | 2308 | 25 | 14.2 | Nil | 0.36 | 8.56 | 10.26 | 4.26 | 14,267 | 69.7 |
| ended; 3 furnaces; 155 lb. | " | " | 24 | 13.9 | " | 0.50 | 8.84 | 10.33 | 4.32 | 14,697 | 68.0 |
| working pressure; closed | " | " | 9 | 30.3 | 0.81 | 0.39 | 7.93 | 9.27 | 8.46 | 14,686 | 61.4 |
| stokehold system.[1] | " | " | 8-1/2| 29.1 | 0.65 | 0.32 | 8.84 | 10.34 | 9.05 | 14,612 | 68.4 |
+----------------------------+-------+--------+--------+-----------+---------+---------+-------+--------+----------+---------+------+
|Ordinary cylindrical single-| |2876 in | | | | | | | | | |
| ended; 3 furnaces; 210 lb. | |boiler, | | | In Ash- | | | | | | |
| working pressure; closed | 63.2 |766 in | 13 | 20.6 | pit | 0.58 | 11.30 | 12.33 | 5.14 | 14,475 | 82.3 |
| ashpit, Howden system.[2] | | air | | | 1.53 | | | | | | |
| | |heaters | | | | | | | | | |
+----------------------------+-------+--------+--------+-----------+---------+---------+-------+--------+----------+---------+------+
|Niclausse water-tube; 160 | 46 | 1322 | 8 | 12.8 | Nil | 0.20 | 8.41 | 10.15 | 3.75 | 14,680 | 66.9 |
| lb. working pressure. | " | " | 8 | 21.9 | " | 0.20 | 8.01 | 9.40 | 6.11 | 14,760 | 62.1 |
| | " | " | 37 | 20.2 | " | 0.29 | 7.62 | 9.00 | 5.44 | 14,600 | 60.5 |
+----------------------------+-------+--------+--------+-----------+---------+---------+-------+--------+----------+---------+------+
|Niclausse water-tube; | 34 | 990 | 9 | 14.0 | 0.10 | 0.23 | 8.77 | 10.50 | 4.17 | 14,640 | 69.8 |
| 250 lb. working pressure. | " | " | 9 | 22.0 | 0.27 | 0.23 | 7.68 | 9.06 | 5.74 | 14,640 | 60.4 |
| | " | " | 90 | 15.4 | Nil |Not asce-| 7.61 | 9.08 | 4.00 | 14,630 | 59.9 |
| | | | | | | rtained | | | | | |
+----------------------------+-------+--------+--------+-----------+---------+---------+-------+--------+----------+---------+------+
|Babcock water-tube; 3-3/16 | 36 | 1010 | 9 | 13.0 | " | 0.26 | 9.31 | 11.02 | 4.30 | 14,590 | 73.2 |
| in. tubes; 260 lb. working | " | " | 9 | 20.0 | 0.18 | 0.20 | 8.58 | 10.11 | 6.13 | 14,590 | 67.0 |
| pressure. | " | " | 90 | 14.5 | Nil |Not asce-| 8.09 | 9.53 | 4.18 | . . | 63.1 |
| | | | | | | rtained | | | | | |
+----------------------------+-------+--------+--------+-----------+---------+---------+-------+--------+----------+---------+------+
|Babcock water-tube; 1-13/16 | 62 | 2167 | 28 | 18.4 | " | 0.45 | 8.94 | 10.61 | 4.61 | 14,520 | 70.7 |
| in. tubes; 270 lb. working | " | " | 24 | 19.2 | " | 0.47 | 8.93 | 10.59 | 4.82 | 14,390 | 71.1 |
| pressure.[3] | " | " | 12 | 20.5 | " | 0.42 | 9.42 | 11.04 | 5.41 | 14,080 | 75.8 |
| | " | " | 7 | 28.9 | 0.50 |Not asce-| 8.54 | 9.88 | 6.91 | 14,390 | 66.3 |
| | | | | | | rtained | | | | | |
| | " | " | 30 | 19.9 | Nil | 0.38 | 10.11 | 12.00 | 6.01 | 14,530 | 79.9 |
| | " | " | 29 | 27.1 | 0.66 | 0.23 | 9.96 | 11.67 | 8.05 | 14,630 | 77.1 |
+----------------------------+-------+--------+--------+-----------+---------+---------+-------+--------+----------+---------+------+
|Belleville water-tube with | 44 | 910 in | 24-1/2| 15.8 | Nil | 0.36 | 9.65 | 11.46 | 4.94 | 14,697 | 77.2 |
| economizers; 320 lb. | " | boiler;| 24 | 17.4 | " | 0.39 | 9.33 | 11.00 | 5.30 | 14,805 | 71.8 |
| working pressure. | " | 447 in | 11 | 19.8 | " | 0.43 | 9.39 | 11.03 | 6.38 | 14,578 | 73.3 |
| | " |economi-| 8 | 27.2 | " | 0.39 | 8.28 | 9.79 | 7.78 | 14,611 | 65.0 |
| | |zer;1357| | | | | | | | | |
| | | total. | | | | | | | | | |
+----------------------------+-------+--------+--------+-----------+---------+---------+-------+--------+----------+---------+------+
|Yarrow water tube; 1-3/4 in.| 56 | 2896 | 26 | 16.9 | Nil | 0.31 | 9.57 | 11.45 | 3.12 | 14,750 | 75.0 |
| tubes; 250 lb. working | " | " | 26 | 18.2 | " | 0.31 | 9.37 | 11.33 | 3.30 | 14,500 | 75.7 |
| pressure. | " | " | 25 | 21.3 | " | 0.31 | 8.83 | 10.45 | 3.63 | 13,500 | 75.2 |
| | " | " | 30 | 35.4 | 0.53 | 0.26 | 8.82 | 10.59 | 6.04 | 14,430 | 70.9 |
| | " | " | 8 | 41.9 | 0.86 | 0.31 | 8.24 | 9.94 | 6.69 | 14,500 | 66.3 |
| | " | " | 8 | 33.7 | 0.31 | 0.30 | 8.39 | 9.93 | 5.47 | 14,680 | 65.4 |
| | " | " | 8 | 39.8 | 0.82 | 0.24 | 8.85 | 10.43 | 6.81 | 14,530 | 69.5 |
+----------------------------+-------+--------+--------+-----------+---------+---------+-------+--------+----------+---------+------+
|Durr water-tube; 250 lb. | 71 |2671 in | 26 | 16.1 | Nil | 0.39 | 7.95 | 9.50 | 3.24 | 14,500 | 63.8 |
| working pressure. | " | boiler;| 26 | 17.7 | " | 0.30 | 7.06 | 9.28 | 3.43 | 14,620 | 61.7 |
| | " | 140 in | 25 | 21.1 | " | 0.31 | 7.62 | 9.08 | 4.05 | 14,650 | 60.3 |
| | " | super- | 7 | 33.8 | 0.70 | 0.36 | 7.72 | 9.29 | 6.59 | 14,570 | 62.7 |
| | " | heater;| 8 | 26.7 | 0.33 | 0.35 | 7.86 | 9.26 | 5.30 | 14,320 | 63.1 |
| | " | 2811 | 8 | 34.6 | 1.11 | 0.20 | 8.02 | 9.53 | 7.02 | 14,230 | 64.8 |
| | " | total. | 22 | 34.8 | 0.73 | 0.16 | 6.84 | 8.06 | 6.02 | 14,430 | 54.0 |
| | " | | 24 | 29.9 | 0.35 | 0.12 | 7.62 | 9.00 | 5.75 | 14,240 | 61.2 |
| | " | | 20 | 19.9 | Nil | 0.21 | 7.30 | 8.33 | 3.66 | 14,240 | 58.6 |
+----------------------------+-------+--------+--------+-----------+---------+---------+-------+--------+----------+---------+------+

[1] In the first three trials no retarders were used in the tubes. In
the last trial retarders were used.

[2] In this trial retarders were used in the tubes.

[3] The first four trials were made with horizontal baffles above the
tubes; the last two trials with the baffling described in the text.

BOILER MAKING.

The practice of the boiler, bridge and girder shops may here be conveniently treated together, because similar materials and methods are employed in each, notwithstanding that many points of divergence in practice generally relegate them to separate departments. The materials used are chiefly iron and steel. The methods mostly adopted are those involved in the working of plates and rolled sections, which vastly predominate over the bars and rods used chiefly in the smithy. But there are numerous differences in methods of construction. Flanging occupies a large place in boilermaking, for end-plates, tube-plates, furnace flues, &c., but is scarcely represented in bridge and girder work. Plates are bent to cylindrical shapes in boilermaking, for shells and furnaces, but not in girder work. Welding is much more common in the first than in the second, furnace flues being always welded and stand pipes frequently. In boiler work holes are generally drilled through the seams of adjacent plates. In bridge work each plate or bar is usually drilled or punched apart from its fellows. Boilers, again, being subject to high temperatures and pressures, must be constructed with provisions to ensure some elasticity and freedom of movement under varying temperatures to prevent fractures or grooving, and must be made of materials that combine high ductility with strength when heated to furnace temperatures. Flanging of certain parts, judicious staying, limitation of the length of the tubes, the forms of which are inherently weak, provide for the first; the selection of steel or iron of high percentage elongation, and the imposition of temper, or bending tests, both hot and cold, provide for the second.

The following are the leading features of present-day methods.

It might be hastily supposed that, because plates, angles, tees,
channels and joist sections are rolled ready for use, little work
could be left for the plater and boilermaker. But actually so much is
involved that subdivisions of tasks are numerous; the operations of
templet-making, rolling, planing, punching and shearing, bending,
welding and forging, flanging, drilling, riveting, caulking, and
tubing require the labours of several groups of machine attendants,
and of gangs of unskilled labourers or helpers. Some operations also
have to be done at a red or white heat, others cold. To the first
belong flanging and welding, to the latter generally all the other
operations. Heating is necessary for the rolling of tubes of small
diameter; bending is done cold or hot according to circumstances.

The fact that some kinds of treatment, as shearing and punching,
flanging and bending, are of a very violent character explains why
practice has changed radically in regard to the method of performing
these operations in cases where safety is a cardinal matter. Shearing
and punching are both severely detrusive operations performed on cold
metal; both leave jagged edges and, as experience has proved, very
minute cracks, the tendency of which is to extend under subsequent
stress, with liability to produce fracture. But it has been found
that, when a shorn edge is planed and a punched hole enlarged by
reamering, no harm results, provided not less than about 1/16 in. is
removed. A great advance was therefore made when specifications first
insisted on the removal of the rough edges before the parts were
united.

In the work of riveting another evil long existed. When holes are
punched it is practically impossible to ensure the exact coincidence
of holes in different plates which have to be brought together for the
purpose of riveting. From this followed the use of the drift,--a
tapered rod driven forcibly by hammer blows through corresponding
holes in adjacent plates, by which violent treatment the holes were
forcibly drawn into alignment. This drifting stressed the plates,
setting up permanent strains and enlarging incipient cracks, and many
boiler explosions have been clearly traceable to the abuse of this
tool. Then, next, specifications insisted that all holes should be
enlarged by reamering _after_ the plates were in place. But even that
did not prove a safeguard, because it often happened that the metal
reamered was nearly all removed from one side of a hole, so leaving
the other side just as the punch had torn it. Ultimately came the era
of drilling rivet-holes, to which there is no exception now in
high-class boiler work. For average girder and bridge work the
practice of punching and reamering is still in use, because the
conditions of service are not so severe as are those in steam boilers.

Flanging signifies the turning or bending over of the edges of a
plate to afford a means of union to other plates. Examples occur in
the back end-plates of Lancashire and Cornish boilers, the front and
back plates of marine boilers, the fire-boxes of locomotive boilers,
the crowns of vertical boilers, the ends of conical cross-tubes, and
the Adamson seams of furnace flues. This practice has superseded the
older system of effecting union by means of rings forming two sides of
a rectangular section (angle iron rings). These were a fruitful source
of grooving and explosions in steam boilers, because their sharp
angular form lacked elasticity; hence the reason for the substitution
of a flange turned with a large radius, which afforded the elasticity
necessary to counteract the effects of changes in temperature. In
girder work where such conditions do not exist, the method of union
with angles is of course retained. In the early days of flanging the
process was performed in detail by a skilled workman (the angle
ironsmith), and it is still so done in small establishments. A length
of edge of about 10 in. or a foot is heated, and bent by hammering
around the edge of a block of iron of suitable shape. Then another
"heat" is taken and flanged, and another, until the work is complete.
But in modern boiler shops little hand work is ever done; instead,
plates 4 ft., 6 ft., or 8 ft. in diameter, and fire-box plates for
locomotive boilers, have their entire flanges bent at a single squeeze
between massive dies in a hydraulic press. In the case of the ends of
marine boilers which are too large for such treatment, a special form
of press bends the edges over in successive heats. The flanges of
Adamson seams are rolled over in a special machine. A length of flue
is rotated on a table, while the flange is turned over within a minute
between revolving rollers. There is another advantage in the adoption
of machine-flanging, besides the enormous saving of time, namely, that
the material suffers far less injury than it does in hand-flanging.

These differences in practice would not have assumed such magnitude
but for the introduction of mild steel in place of malleable iron.
Iron suffers less from overheating and irregular heating than does
steel. Steel possesses higher ductility, but it is also more liable to
develop cracks if subjected to improper treatment. All this and much
more is writ large in the early testing of steel, and is reflected in
present-day practice.

A feature peculiar to the boiler and plating shops is the enormous
number of rivet holes which have to be made, and of rivets to be
inserted. These requirements are reflected in machine design. To punch
or drill holes singly is too slow a process in the best practice, and
so machines are made for producing many holes simultaneously. Besides
this, the different sections of boilers are drilled in machines of
different types, some for shells, some for furnaces, some peculiar to
the shells or furnaces of one type of boilers, others to those of
another type only. And generally now these machines not only drill,
but can also be adjusted to drill to exact pitch, the necessity thus
being avoided of marking out the holes as guides to the drills.

Hand-riveting has mostly been displaced by hydraulic and pneumatic
machines, with resulting great saving in cost, and the advantage of
more trustworthy and uniform results. For boiler work, machines are
mostly of fixed type; for bridge and girder work they are portable,
being slung from chains and provided with pressure water or compressed
air by systems of flexible pipes.

Welding fills a large place in boiler work, but it is that of the
edges of plates chiefly, predominating over that of the bars and rods
of the smithy. The edges to be united are thin and long, so that short
lengths have to be done in succession at successive "heats." Much of
this is hand work, and "gluts" or insertion pieces are generally
preferred to overlapping joints. But in large shops, steam-driven
power hammers are used for closing the welds. Parts that are commonly
welded are the furnace flues, the conical cross-tubes and angle rings.

Another aspect of the work of these departments is the immense
proportions of the modern machine tools used. This development is due
in great degree to the substitution of steel for iron. The steel
shell-plates of the largest boilers are 1-1/2 in. thick, and these
have to be bent into cylindrical forms. In the old days of iron
boilers the capacity of rolls never exceeded about 3/4 in. plate.
Often, alternatively to rolling, these thick plates are bent by
squeezing them in successive sections between huge blocks operated by
hydraulic pressure acting on toggle levers. And other machines besides
the rolls are made more massive than formerly to deal with the immense
plates of modern marine boilers.

The boiler and plating shops have been affected by the general
tendency to specialize manufactures. Firms have fallen into the
practice of restricting their range of product, with increase in
volume. The time has gone past when a single shop could turn out
several classes of boilers, and undertake any bridge and girder work
as well. One reason is to be found in the diminution of hand work and
the growth of the machine tool. Almost every distinct operation on
every section of a boiler or bridge may now be accomplished by one of
several highly specialized machines. Repetitive operations are
provided for thus, and by a system of templeting. If twenty or fifty
similar boilers are made in a year, each plate, hole, flange or stay
will be exactly like every similar one in the set. Dimensions of
plates will be marked from a sample or templet plate, and holes will
be marked similarly; or in many cases they are not marked at all, but
pitched and drilled at once by self-acting mechanism embodied in
drilling machines specially designed for one set of operations on one
kind of plate. Hundreds of bracing bars for bridges and girders will
be cut off all alike, and drilled or punched from a templet bar, so
that they are ready to take their place in bridge or girder without
any adjustments or fitting. (J. G. H.)

BOILING TO DEATH, a punishment once common both in England and on the continent. The only extant legislative notice of it in England occurs in an act passed in 1531 during the reign of Henry VIII., providing that convicted poisoners should be boiled to death; it is, however, frequently mentioned earlier as a punishment for coining. The _Chronicles of the Grey Friars_ (published by the Camden Society, 1852) have an account of boiling for poisoning at Smithfield in the year 1522, the man being fastened to a chain and lowered into boiling water several times until he died. The preamble of the statute of Henry VIII. (which made poisoning treason) in 1531 recites that one Richard Roose (or Coke), a cook, by putting poison in some food intended for the household of the bishop of Rochester and for the poor of the parish of Lambeth, killed a man and woman. He was found guilty of treason and sentenced to be boiled to death without benefit of clergy. He was publicly boiled at Smithfield. In the same year a maid-servant for poisoning her mistress was boiled at King's Lynn. In 1542 Margaret Davy, a servant, for poisoning her employer, was boiled at Smithfield. In the reign of Edward VI., in 1547, the act was repealed.

See also W. Andrews, _Old Time Punishments_ (Hull, 1890); _Notes and
Queries_, vol. i. (1862), vol. ix. (1867); Du Cange (s.v. _Caldariis
decoquere_).

BOIS BRULES, or BRULES (a French translation of their Indian name SICHANGU), a sub-tribe of North American Dakota Indians (Teton river division). The name is most frequently associated with the half-breeds in Manitoba, who in 1869 came into temporary prominence in connexion with Riel's Rebellion (see RED RIVER); at that time they had lost all tribal purity, and were alternatively called _Metis_ (half-castes), the majority being descendants of French-Canadians.

BOISE, a city and the county-seat of Ada county, Idaho, U.S.A., and the capital of the state, situated on the N. side of the Boise river, in the S.W. part of the state, at an altitude of about 2700 ft. Pop. (1890) 2311; (1900) 5957; (1910) 17,358. It is served by the Oregon Short Line railway, being the terminus of a branch connecting with the main line at Nampa, about 20 m. W.; and by electric lines connecting with Caldwell and Nampa. The principal buildings are the state capitol, the United States assay office, a Carnegie library, a natatorium, and the Federal building, containing the post office, the United States circuit and district court rooms, and a U.S. land office. Boise is the seat of the state school for the deaf and blind (1906), and just outside the city limits are the state soldiers' home and the state penitentiary. About 2 m. from the city are Federal barracks. Hot water (175 deg. F.) from artesian wells near the city is utilized for the natatorium and to heat many residences and public buildings. The Boise valley is an excellent country for raising apples, prunes and other fruits. The manufactured products of the city are such as are demanded by a mining country, principally lumber, flour and machine-shop products. Boise is the trade centre of the surrounding fruit-growing, agricultural and mining country, and is an important wool market. The oldest settlement in the vicinity was made by the Hudson's Bay Fur Company on the west side of the Boise river, before 1860; the present city, chartered in 1864, dates from 1863. After 1900 the city grew very rapidly, principally owing to the great irrigation schemes in southern Idaho; the water for the immense Boise-Payette irrigation system is taken from the Boise, 8 m. above the city. (See IDAHO.)

BOISGOBEY, FORTUNE DU (1824-1891), French writer of fiction, whose real surname was Castille, was born at Granville (Manche) on the 11th of September 1824. He served in the army pay department in Algeria from 1844 to 1848, and extended his travels to the East. He made his literary debut in the _Petit journal_ with a story entitled _Deux comediens_ (1868). With _Le Forcat colonel_ (1872) he became one of the most popular feuilleton writers. His police stories, though not so convincing as those of Emile Gaboriau, with whom his name is generally associated, had a great circulation, and many of them have been translated into English. Among his stories may be mentioned: _Les Mysteres du nouveau Paris_ (1876), _Le Demi-Monde sous la Terreur_ (1877), _Les Nuits de Constantinople_ (1882), _Le Cri du sang_ (1885), _La Main froide_ (1889). Boisgobey died on the 26th of February 1891.

BOISGUILBERT, PIERRE LE PESANT, SIEUR DE (1676-1714), French economist, was born at Rouen of an ancient noble family of Normandy, allied to that of Corneille. He received his classical education in Rouen, entered the magistracy and became judge at Montivilliers, near Havre. In 1690 he became president of the _bailliage_ of Rouen, a post which he retained almost until his death, leaving it to his son. In these two situations he made a close study of local economic conditions, personally supervising the cultivation of his lands, and entering into relations with the principal merchants of Rouen. He was thus led to consider the misery of the people under the burden of taxation. In 1695 he published his principal work, _Le Detail de la France; la cause de la diminution de ses biens, et la facilite du remede_.... In it he drew a picture of the general ruin of all classes of Frenchmen, caused by the bad economic regime. In opposition to Colbert's views he held that the wealth of a country consists, not in the abundance of money which it possesses but in what it produces and exchanges. The remedy for the evils of the time was not so much the reduction as the equalization of the imposts, which would allow the poor to consume more, raise the production and add to the general wealth. He demanded the reform of the _taille_, the suppression of internal customs duties and greater freedom of trade. In his _Factum de la France_, published in 1705 or 1706, he gave a more concise _resume_ of his ideas. But his proposal to substitute for all aides and customs duties a single capitation tax of a tenth of the revenue of all property was naturally opposed by the farmers of taxes and found little support. Indeed his work, written in a diffuse and inelegant style, passed almost unnoticed. Saint Simon relates that he once asked a hearing of the comte de Pontchartrain, saying that he would at first believe him mad, then become interested, and then see he was right. Pontchartrain bluntly told him that he did think him mad, and turned his back on him. With Michel de Chamillart, whom he had known as intendant of Rouen (1689-1690), he had no better success. Upon the disgrace of Vauban, whose _Dime royale_ had much in common with Boisguilbert's plan, Boisguilbert violently attacked the controller in a pamphlet, _Supplement au detail de la France_. The book was seized and condemned, and its author exiled to Auvergne, though soon allowed to return. At last in 1710 the controller-general, Nicolas Desmarets, established a new impost, the "tenth" (_dixieme_), which had some analogy with the project of Boisguilbert. Instead of replacing the former imposts, however, Desmarets simply added his _dixieme_ to them; the experiment was naturally disastrous, and the idea was abandoned.

In 1712 appeared a _Testament politique de M. de Vauban_, which is
simply Boisguilbert's _Detail de la France_. Vauban's _Dime royale_
was formerly wrongly attributed to him. Boisguilbert's works were
collected by Daire in the first volume of the _Collection des grands
economistes_. His letters are in the _Correspondance des controleurs
generaux_, vol. i., published by M. de Boislisle.

BOISROBERT, FRANCOIS LE METEL DE (1592-1662), French poet, was born at Caen in 1592. He was trained for the law, and practised for some time at the bar at Rouen. About 1622 he went to Paris, and by the next year had established a footing at court, for he had a share in the ballet of the _Bacchanales_ performed at the Louvre in February. He accompanied an embassy to England in 1625, and in 1630 visited Rome, where he won the favour of Urban VIII. by his wit. He took orders, and was made a canon of Rouen. He had been introduced to Richelieu in 1623, and by his humour and his talent as a raconteur soon made himself indispensable to the cardinal. Boisrobert became one of the five poets who carried out Richelieu's dramatic ideas. He had a passion for play, and was a friend of Ninon de l'Enclos; and his enemies found ready weapons against him in the undisguised looseness of his life. He was more than once disgraced, but never for long, although in his later years he was compelled to give more attention to his duties as a priest. It was Boisrobert who suggested to Richelieu the plan of the Academy, and he was one of its earliest and most active members. Rich as he was through the benefices conferred on him by his patron, he was liberal to men of letters. After the death of Richelieu, he attached himself to Mazarin, whom he served faithfully throughout the Fronde. He died on the 30th of March 1662. He wrote a number of comedies, to one of which, _La Belle Plaideuse_, Moliere's _L'Avare_ is said to owe something; and also some volumes of verse. The licentious _Contes_, published under the name of his brother D'Ouville, are often attributed to him.

BOISSARD, JEAN JACQUES (1528-1602), French antiquary and Latin poet, was born at Besancon. He studied at Louvain; but, disgusted by the severity of his master, he secretly left that seminary, and after traversing a great part of Germany reached Italy, where he remained several years and was often reduced to great straits. His residence in Italy developed in his mind a taste for antiquities, and he soon formed a collection of the most curious monuments from Rome and its vicinity. He then visited the islands of the Archipelago, with the intention of travelling through Greece, but a severe illness obliged him to return to Rome. Here he resumed his favourite pursuits with great ardour, and having completed his collection, returned to his native country; but not being permitted to profess publicly the Protestant religion, which he had embraced some time before, he withdrew to Metz, where he died on the 30th of October 1602. His most important works are: _Poemata_ (1574); _Emblemata_ (1584); _Icones Virorum Illustrium_ (1597); _Vitae et Icones Sultanorum Turcicorum_, &c. (1597); _Theatrum Vitae Humanae_ (1596); _Romanae Urbis Topographia_ (1597-1602), now very rare; _De Divinatione et Magicis Praestigiis_ (1605); _Habitus Variarum Orbis Gentium_ (1581), ornamented with seventy illuminated figures.

BOISSIER, MARIE LOUIS ANTOINE GASTON (1823-1908), French classical scholar, and secretary of the French Academy, was born at Nimes on the 15th of August 1823. The Roman monuments of his native town very early attracted Gaston Boissier to the study of ancient history. He made epigraphy his particular theme, and at the age of twenty-three became a professor of rhetoric at Angouleme, where he lived and worked for ten years without further ambition. A travelling inspector of the university, however, happened to hear him lecture, and Boissier was called to Paris to be professor at the Lycee Charlemagne. He began his literary career by a thesis on the poet Attius (1857) and a study on the life and work of M. Terentius Varro (1861). In 1861 he was made professor of Latin oratory at the College de France, and he became an active contributor to the _Revue des deux mondes_. In 1865 he published _Ciceron et ses amis_ (Eng. trans, by A.D. Jones, 1897), which has enjoyed a success such as rarely falls to the lot of a work of erudition. In studying the manners of ancient Rome, Boissier had learned to re-create its society and to reproduce its characteristics with exquisite vivacity. In 1874 he published _La Religion romaine d'Auguste aux Antonins_ (2 vols.), in which he analysed the great religious movement of antiquity that preceded the acceptance of Christianity. In _L'Opposition sous les Cesars_ (1875) he drew a remarkable picture of the political decadence of Rome under the early successors of Augustus. By this time Boissier had drawn to himself the universal respect of scholars and men of letters, and on the death of H.J.G. Patin, the author of _Etudes sur les tragiques grecs_, in 1876, he was elected a member of the French Academy, of which he was appointed perpetual secretary in 1895.

His later works include _Promenades archeologiques: Rome et Pompei_ (1880; second series, 1886); _L'Afrique romaine, promenades archeologiques_ (1901); _La Fin du paganisme_ (2 vols., 1891); _Le Conjuration de Catilina_ (1905); _Tacite_ (1903, Eng. trans, by W.G. Hutchison, 1906). He was a representative example of the French talent for lucidity and elegance applied with entire seriousness to weighty matters of literature. Though he devoted himself mainly to his great theme, the reconstruction of the elements of Roman society, he also wrote monographs on _Madame de Sevigne_ (1887) and _Saint-Simon_ (1892). He died in June 1908.

BOISSONADE DE FONTARABIE, JEAN FRANCOIS (1774-1857), French classical scholar, was born at Paris on the 12th of August 1774. In 1792 he entered the public service during the administration of General Dumouriez. Driven from it in 1795, he was restored by Lucien Bonaparte, during whose time of office he served as secretary to the prefecture of the Upper Marne. He then definitely resigned public employment and devoted himself to the study of Greek. In 1809 he was appointed deputy professor of Greek at the faculty of letters at Paris, and titular professor in 1813 on the death of P.H. Larcher. In 1828 he succeeded J.B. Gail in the chair of Greek at the College de France. He also held the offices of librarian of the Bibliotheque du Roi, and of perpetual secretary of the Academie des Inscriptions. He died on the 8th of September 1857. Boissonade chiefly devoted his attention to later Greek literature: Philostratus, _Heroica_ (1806) and _Epistolae_ (1842); Marinus, _Vita procli_ (1814); Tiberius Rhetor, _De Figuris_ (1815); Nicetas Eugenianus, _Drosilla et Charicles_ (1819); Herodian, _Partitiones_ (1819); Aristaenetus, _Epistolae_ (1822); Eunapius, _Vitae Sophistarum_ (1822); Babrius, _Fables_ (1844); Tzetzes, _Allegoriae Iliados_ (1851); and a _Collection of Greek Poets_ in 24 vols. The _Anecdota Graeca_ (1829-1833) and _Anecdota Nova_ (1844) are important for Byzantine history and the Greek grammarians.

A selection of his papers was published by F. Colincamp, _Critique
litteraire sous le premier Empire_ (1863), vol. i. of which contains a
complete list of his works, and a "Notice Historique sur Monsieur B.,"
by Naudet.

BOISSY D'ANGLAS, FRANCOIS ANTOINE DE (1756-1828), French statesman, received a careful education and busied himself at first with literature. He had been a member of several provincial academies before coming to Paris, where he purchased a position as advocate to the parlement. In 1789 he was elected by the third estate of the _senechaussee_ of Annonay as deputy to the states-general. He was one of those who induced the states-general to proclaim itself a National Assembly on the 17th of June 1789; approved, in several speeches, of the capture of the Bastille and of the taking of the royal family to Paris (October 1789); demanded that strict measures be taken against the royalists who were intriguing in the south of France, and published some pamphlets on finance. During the Legislative Assembly he was _procureur-syndic_ for the directory of the department of Ardeche. Elected to the Convention, he sat in the centre, "_le Marais_," voting in the trial of Louis XVI. for his detention until deportation should be judged expedient for the state. He was then sent on a mission to Lyons to investigate the frauds in connexion with the supplies of the army of the Alps. During the Terror he was one of those deputies of the centre who supported Robespierre; but he was gained over by the members of the Mountain hostile to Robespierre, and his support, along with that of some other leaders of the _Marais_, made possible the 9th Thermidor. He was then elected a member of the Committee of Public Safety and charged with the superintendence of the provisioning of Paris. He presented the report supporting the decree of the 3rd Ventose of the year III. which established liberty of worship. In the critical days of Germinal and of Prairial of the year III. he showed great courage. On the 12th Germinal he was in the tribune, reading a report on the food supplies, when the hall of the Convention was invaded by the rioters, and when they withdrew he quietly continued where he had been interrupted. On the 1st Prairial he presided over the Convention, and remained unmoved by the insults and menaces of the insurgents. When the head of the deputy, Jean Feraud, was presented to him on the end of a pike, he saluted it impassively. He was reporter of the committee which drew up the constitution of the year III., and his report shows keen apprehension of a return of the Reign of Terror, and presents reactionary measures as precautions against the re-establishment of "tyranny and anarchy." This report, the proposal that he made (August 27, 1795) to lessen the severity of the revolutionary laws, and the eulogies he received from several Paris sections suspected of disloyalty to the republic, resulted in his being obliged to justify himself (October 15, 1795). As a member of the Council of the Five Hundred he became more and more suspected of royalism. He presented a measure in favour of full liberty for the press, which at that time was almost unanimously reactionary, protested against the outlawry of returned _emigres_, spoke in favour of the deported priests and attacked the Directory. Accordingly he was proscribed on the 18th Fructidor, and lived in England until the Consulate. In 1801 he was made a member of the Tribunate, and in 1805 a senator. In 1814 he voted for Napoleon's abdication, which won for him a seat in the chamber of peers; but during the Hundred Days he served Napoleon, and in consequence, on the second Restoration, was for a short while excluded. In the chamber he still sought to obtain liberty for the press--a theme upon which he published a volume of his speeches (Paris, 1817). He was a member of the Institute from its foundation, and in 1816, at the reorganization, became a member of the Academie des Inscriptions et Belles-Lettres. He published in 1819-1821 a two-volume _Essai sur la vie et les opinions de M. de Malesherbes_.

See F.A. Aulard, _Les Orateurs de la Revolution_ (2nd ed., 1906); L.
Sciout, _Le Directoire_ (4 vols., 1895); and the "Notice sur la vie et
les oeuvres de M. Boissy d'Anglas" in the _Memoires de l'Academie des
Inscriptions_, ix. (R. A.*)