Chapter XI: Front Matter (11)

As usually happens in similar cases, the name of the once familiar British species is now used in a general sense, and applied to all others which are allied to it. Though by former systematists placed near or even among the herons, there is no doubt that the cranes have only a superficial resemblance and no real affinity to the _Ardeidae_. In fact the _Gruidae_ form a somewhat isolated group. Huxley included them together with the _Rallidae_ in his _Geranomorphae_; but a more extended view of their various characters would probably assign them rather as relatives of the Bustards--not that it must be thought that the two families have not been for a very long time distinct. _Grus_, indeed, is a very ancient form, its remains appearing in the Miocene of France and Greece, as well as in the Pliocene and Post-pliocene of North America. In France, too, during the "Reindeer Period" there existed a huge species--the _G. primigenia_ of Alphonse Milne-Edwards--which has doubtless been long extinct. At the present time cranes inhabit all the great zoogeographical regions of the earth, except the Neotropical, and some sixteen or seventeen species are discriminated. In Europe, besides the _G. communis_ already mentioned, the Numidian or demoiselle-crane (_G. virgo_) is distinguished from every other by its long white ear-tufts. This bird is also widely distributed throughout Asia and Africa, and is said to have occurred in Orkney as a straggler. The eastern part of the Palaearctic Region is inhabited by four other species that do not frequent Europe (_G. antigone_, _G. japonensis_, _G. monachus_, and _G. leucogeranus_), of which the last is perhaps the finest of the family, with nearly the whole plumage of a snowy white. The Indian Region, besides being visited in winter by four of the species already named, has two that are peculiar to it (_G. torquata_ and _G. indica_, both commonly confounded under the name of _G. antigone_). The Australian Region possesses a large species known to the colonists as the "native companion" (_G. australis_), while the Nearctic is tenanted by three species (_G. americana_, _G. canadensis_ and _G. fraterculus_), to say nothing of the possibility of a fourth (_G. schlegeli_), a little-known and somewhat obscure bird, finding its habitat here. In the Ethiopian Region are two species (_G. paradisea_ and _G. carunculata_), which do not occur out of Africa, as well as three others forming the group known as "crowned cranes"--differing much from other members of the family, and justifiably placed in a separate genus, _Balearica_. One of these (_B. pavonina_) inhabits northern and western Africa, while another (_B. regulorum_) is confined to the eastern and southern parts of that continent. The third (_B. ceciliae_), from the White Nile, has been described by Dr P. Chalmers Mitchell (_P.Z.S._, 1904).

With regard to the literature of this species, a paper "On the
Breeding of the Crane in Lapland" (_Ibis_, 1859, p. 191), by John
Wolley, is one of the most pleasing contributions to natural history
ever written, and an admirably succinct account of all the different
species was communicated by Blyth to _The Field_ in 1873 (vol. xl. p.
631, vol. xli. pp. 7, 61, 136, 189, 248, 384, 408, 418). A beautiful
picture representing a flock of cranes resting by the Rhine during one
of their annual migrations is to be found in Wolf's _Zoological
Sketches_. (A. N.)

CRANES (so called from the resemblance to the long neck of the bird, cf. Gr. [Greek: geranos], Fr. _grue_), machines by means of which heavy bodies may be lifted, and also displaced horizontally, within certain defined limits. Strictly speaking, the name alludes to the arm or jib from which the load to be moved is suspended, but it is now used in a wider sense to include the whole mechanism by which a load is raised vertically and moved horizontally. Machines used for lifting only are not called cranes, but winches, lifts or hoists, while the term elevator or conveyor is commonly given to appliances which continuously, not in separate loads, move materials like grain or coal in a vertical, horizontal or diagonal direction (see CONVEYORS). The use of cranes is of great antiquity, but it is only since the great industrial development of the 19th century, and the introduction of other motive powers than hand labour, that the crane has acquired the important and indispensable position it now occupies. In all places where finished goods are handled, or manufactured goods are made, cranes of various forms are in universal use.

Classification.

Cranes may be divided into two main classes--revolving and non-revolving. In the first the load can be lifted vertically, and then moved round a central pivot, so as to be deposited at any convenient point within the range. The type of this class is the ordinary jib crane. In the second class there are, in addition to the lifting motion, two horizontal movements at right angles to one another. The type of this class is the overhead traveller. The two classes obviously represent respectively systems of polar and rectangular coordinates. Jib cranes can be subdivided into fixed cranes and portable cranes; in the former the central-post or pivot is firmly fixed in a permanent position, while in the latter the whole crane is mounted on wheels, so that it may be transported from place to place.

Motive powers.

The different kinds of motive power used to actuate cranes--manual, steam, hydraulic, electric--give a further classification. Hand cranes are extremely useful where the load is not excessive, and the quantities to be dealt with are not great; also where speed is not important, and first cost is an essential consideration. The net effective work of lifting that can be performed by a man turning a handle may be taken, for intermittent work, as being on an average about 5000 foot-lb per minute; this is equivalent to 1 ton lifted about 2-1/4 ft. per minute, so that four men can by a crane raise 1 ton 9 ft. in a minute or 9 tons 1 ft. per minute. It is at once evident that hand power is only suitable for cranes of moderate power, or in cases where heavy loads have to be lifted only very occasionally. This point is dwelt upon, because the speed limitations of the hand-crane are often overlooked by engineers. Steam is an extremely useful motive power for all cranes that are not worked off a central power station. The steam crane has the immense advantage of being completely self-contained. It can be moved (by its own locomotive power, if desired) long distances without requiring any complicated means of conveying power to it; and it is rapid in work, fairly economical, and can be adapted to the most varying circumstances. Where, however, there are a number of cranes all belonging to the same installation, and these are placed so as to be conveniently worked from a central power station, and where the work is rapid, heavy and continuous, as is the case at large ports, docks and railway or other warehouses, experience has shown that it is best to produce the power in a generating station and distribute it to the cranes. Down to the closing decades of the 19th century hydraulic power was practically the only system available for working cranes from a power station. The hydraulic crane is rapid in action, very smooth and silent in working, easy to handle, and not excessive in cost or upkeep,--advantages which have secured its adoption in every part of the world. Electricity as a motive power for cranes is of more recent introduction. The electric transmission of energy can be performed with an efficiency not reached by any other method, and the electric motor readily adapts itself to cranes. When they are worked from a power station the great advantage is gained that the same plant which drives them can be used for many other purposes, such as working machine tools and supplying current for lighting. For dock-side jib cranes the use of electric power is making rapid strides. For overhead travellers in workshops, and for most of the cranes which fall into our second class, electricity as a motive power has already displaced nearly every other method. Cranes driven by shafting, or by mechanical power, have been largely superseded by electric cranes, principally on account of the much greater economy of transmission. For many years the best workshop travellers were those driven by quick running ropes; these performed admirable service, but they have given place to the more modern electric traveller.

Lifting mechanisms.

The principal motion in a crane is naturally the hoisting or lifting
motion. This is effected by slinging the load to an eye or hook, and
elevating the hook vertically. There are three typical methods: (1) A
direct pull may be applied to the hook, either by screws, or by a
cylinder fitted with piston and rod and actuated by direct hydraulic
or other pressure, as shown diagrammatically in fig. 1. These methods
are used in exceptional cases, but present the obvious difficulty of
giving a very short range of lift. (2) The hook may be attached to a
rope or chain, and the pulling cylinder connected with a system of
pulleys around which the rope is led; by these means the lift can be
very largely increased. Various arrangements are adopted; the one
indicated in fig. 2 gives a lift of load four times the stroke of the
cylinder. This second method forms the basis of the lifting gear in
all hydraulic cranes. (3) The lifting rope or chain is led over pulley
to a lifting barrel, upon which it is coiled as the barrel is rotated
by the source of power (fig. 3). Sometimes, especially in the case of
overhead travelling cranes for very heavy loads, the chain is a
special pitch chain, formed of flat links pinned together, and the
barrel is reduced to a wheel provided with teeth, or "sprockets,"
which engage in the links. In this case the chain is not coiled, but
simply passes over the lifting wheel, the free end hanging loose. All
the methods in this third category require a rotating lifting or
barrel shaft, and this is the important difference between them and
the hydraulic cranes mentioned above. Cranes fitted with rotating
hydraulic engines may be considered as coming under the third
category.

When the loads are heavy the above mechanisms are supplemented by
systems of purchase blocks suspended from the jib or the traveller
crab; and in barrel cranes trains of rotating gearing are interposed
between the motor, or manual handle, and the barrel (fig. 3).

Brakes.

When a load is lifted, work has to be done in overcoming the action of
gravity and the friction of the mechanism; when it is lowered, energy
is given out. To control the speed and absorb this energy, brakes have
to be provided. The hydraulic crane has a great advantage in
possessing an almost ideal brake, for by simply throttling the exhaust
from the lifting cylinder the speed of descent can be regulated within
very wide limits and with perfect safety. Barrel cranes are usually
fitted with band brakes, consisting of a brake rim with a friction
band placed round it, the band being tightened as required. In
ordinary cases conduction and convection suffice to dissipate the heat
generated by the brake, but when a great deal of lowering has to be
rapidly performed, or heavy loads have to be lowered to a great depth,
special arrangements have to be provided. An excellent brake for very
large cranes is Matthew's hydraulic brake, in which water is passed
from end to end of cylinders fitted with reciprocating pistons,
cooling jackets being provided. In electric cranes a useful method is
to arrange the connexions so that the lifting motor acts as a dynamo,
and, driven by the energy of the falling load, generates a current
which is converted into heat by being passed through resistances. That
the quantity of heat to be got rid of may become very considerable is
seen when it is considered that the energy of a load of 60 tons
descending through 50 ft. is equivalent to an amount of heat
sufficient to raise nearly 6 gallons of water from 60 deg. F. to
boiling point. Crane brakes are usually under the direct control of
the driver, and they are generally arranged in one of two ways. In the
first, the pressure is applied by a handle or treadle, and is removed
by a spring or weight; this is called "braking on." In the second, or
"braking off" method, the brake is automatically applied by a spring
or weight, and is released either mechanically or, in the case of
electric cranes, by the pull of a solenoid or magnet which is
energized by the current passing through the motor. When the motor
starts the brake is released; when it stops, or the current ceases,
the brake goes on. The first method is in general use for steam
cranes; it allows for a far greater range of power in the brake, but
is not automatic, as is the second.

In free-barrel cranes the lifting barrel is connected to the revolving
shaft by a powerful friction clutch; this, when interlocked with the
brake and controller, renders electric cranes exceedingly rapid in
working, as the barrel can be detached and lowering performed at a
very high speed, without waiting for the lifting motor to come to rest
in order to be reversed. This method of working is very suitable for
electric dock-side cranes of capacities up to about 5 or 7 tons, and
for overhead travellers where the height of lift is moderate. Where
high speed lowering is not required it is usual to employ a reversing
motor and keep it always in gear.

In steam cranes it is usual to work all the motions from one double
cylinder engine. In order to enable two or more motions to be worked
together, or independently as required, reversing friction cones are
used for the subsidiary motions, especially the slewing motion. With
the exception of a few special cranes in which friction wheels are
employed, it is universally the practice, in steam cranes, to connect
the engine shaft with the barrel shaft by spur toothed gearing, the
gear being connected or disconnected by sliding pinions. In electric
cranes the motor is connected to the barrel, either in a similar
manner by spur gear or by worm gear. The toothed wheels give a
slightly better efficiency, but the worm gear is somewhat smoother in
its action and entirely silent; the noise of gearing can, however, be
considerably reduced by careful machining of the teeth, as is now
always done, and also by the use of pinions made of rawhide leather or
other non-resonant material. When quick-running metal pinions are used
they are arranged to run in closed oil-baths. Leather pinions must be
protected from rats, which eat them freely. Worm wheel gearing is of
very high efficiency if made very quick in pitch, with properly formed
teeth perfectly lubricated, and with the end thrust of the worm taken
on ball bearings. Much attention has been paid to the improvement of
the mechanical details of the lifting and other motions of cranes, and
in important installations the gearing is now usually made of cast
steel. In revolving cranes ease of slewing can be greatly increased by
the use of a live ring of conical rollers.

Power required.

Electric motors for barrel cranes are not essentially different from
those used for other purposes, but in proportioning the sizes the
intermittent output has to be taken into consideration. This fact has
led to the introduction of the "crane rated" motor, with a given "load
factor." This latter gives the ratio of the length of the working
periods to the whole time; e.g. a motor rated for a quarter load
factor means that the motor is capable of exerting its full normal
horse-power for three minutes out of every twelve, the pause being
nine minutes, or one minute out of every four, the pause being three
minutes. The actual load factor to be chosen depends on the nature of
the work and the kind of crane. A dock-side crane unloading cargo with
high lifts following one another in rapid succession will require a
higher load factor than a workshop traveller with a very short lift
and only a very occasional maximum load; and a traveller with a very
long longitudinal travel will require a higher load factor for the
travelling motor than for the lifting motor. In practice, the load
factor for electric crane motors varies from 1/3 to 1/6. In steam
cranes much the same principle obtains in proportioning the boiler;
e.g. the engines of a 10-ton steam crane have cylinders capable of
indicating about 60 horse-power when working at full speed, but it is
found that, in consequence of the intermittent working, sufficient
steam can be supplied with a boiler whose heating surface is only 1/3
to 1/4 of that necessary for the above power, when developed
continuously by a stationary engine.

In well-designed, quick-running cranes the mechanical efficiency of
the lifting gear may be taken as about 85%; a good electric jib crane
will give an efficiency of 72%, i.e. when actually lifting at full
speed the mechanical work of lifting represents about 72% of the
electric energy put into the lifting motor. A very convenient rule is
to allow one brake horse-power of motor for every 10 foot-tons of work
done at the hook: this is equivalent to an efficiency of 66-2/3%, and
is well on the safe side.

The motor in most common use for electric cranes is the series wound,
continuous current motor, which has many advantages. It has a very
large starting torque, which enables it to overcome the inertia of
getting the load into motion, and it lifts heavy loads at a slower
speed and lighter loads at a quicker one, behaving, under the action
of the controller in a somewhat similar manner to that in which the
cylinders of the steam crane respond to the action of the stop-valve.
Three-phase motors are also much used for crane-driving, and it is
probable that improvements in single and two-phase motors will
eventually largely increase their use for this class of work.

Tests of the comparative efficiencies of hydraulic and electric cranes
tend to show that, although they do not vary to any very considerable
extent with full load, yet the efficiency of the hydraulic crane falls
away very much more rapidly than that of the electric crane when
working on smaller loads. This drawback can be corrected to a slight
extent by furnishing the hydraulic crane with more than one cylinder,
and thus compounding it, but the arrangement does not give the same
economical range of load as in an electric crane. In first cost the
hydraulic crane has the advantage, but the power mains are much less
expensive and more convenient to arrange in the electric crane.

Speed.

The limit of speed of lift of hand cranes has already been mentioned;
for steam jib cranes average practice is represented by the formula V
= 30 + 200/T, where V is the speed of lift in feet per minute, and T
the load in tons. Where electric or hydraulic cranes are worked from a
central station the speed is greater, and may be roughly represented
by V = 5 + 300/T; e.g. a 30-cwt. crane would lift with a speed of
about 200 ft. per minute, and 100-ton crane with a speed of about 8
ft. per minute, but these speeds vary with local circumstances. The
lifting speed of electric travellers is generally less, because the
lift is generally much shorter, and may in ordinary cases be taken as
V = 3 + 85/T. The cross-traversing speed of travellers varies from 60
to 120 ft. per minute, and the longitudinal from 100 to 300 ft. per
minute. The speed of these two motions depends much on the length of
the span and of the longitudinal run, and on the nature of the work to
be done; in certain cases, e.g. foundries, it is desirable to be able
to lift, on occasions, at an extremely slow speed. In addition to the
brakes on the lifting gear of cranes it is found necessary, especially
in quick-running electric cranes, to provide a brake on the subsidiary
motions, and also devices to stop the motor at the end of the lift or
travel, so as to prevent over-running.

There are many other important points of crane construction too
numerous to mention here, but it may be said generally that the advent
of electricity has tended to increase speeds, and in consequence great
attention is paid to all details that reduce friction and wear, such
as roller and ball bearings and improved methods of lubrication; and,
as in all other quick-running machinery, great stress has to be laid
on accuracy of workmanship. The machinery, thus being of a higher
class, requires more protection, and cranes that work in the open are
now fitted with elaborate crane-houses or cabins, furnished with
weather-tight doors and windows, and more care is taken to provide
proper platforms, hand-rails and ladders of access, and also guards
for the revolving parts of gearing.

Fixed Cranes.

_Typical Forms of Cranes._--Fig. 4 is a diagram of a fixed hand
revolving jib crane, of moderate size, as used in railway goods yards
and similar places. It consists of a heavy base, which is securely
bolted to the foundation, and which carries the strong crane-post, or
pillar, around which the crane revolves. The revolving part is made
with two side frames of cast iron or steel plates, and to these the
lifting gear is attached. The load is suspended from the crane jib;
this jib is attached at the lower end to the side frames, and the
upper end is supported by tie-rods, connected to the framework, the
whole revolving together. This simple form of crane thus embodies the
essential elements of foundation, post, framework, jib, tie-rods and
gearing.

Fig. 5 shows another type of fixed crane, known as a derrick crane.
Here the crane-post is extended into a long mast and is furnished with
pivots at the top and bottom; the mast is supported by two "back
ties," and these are connected to the socket of the bottom pivot by
the "sleepers." This is a very good and comparatively cheap form of
crane, where a long and variable radius is required, but it cannot
slew through a complete circle. Derrick cranes are made of all powers,
from the timber 1-ton hand derrick to the steel 150-ton derrick used
in shipbuilding yards. The derrick crane introduces a problem for
which many solutions have been sought, that of preventing the load
from being lifted or lowered when the jib is pivoted up or down to
alter the radius. To keep the load level, there are various devices
for automatically coupling the jib-raising and the load-lowering
motions.

Somewhat allied to the derrick are the sheer legs (fig. 6). Here the
place of the jib is taken by two inclined legs joined together at the
top and pivoted at the bottom; a third back-leg is connected at the
top to the other two, and at the bottom is coupled to a nut which runs
on a long horizontal screw. This horizontal movement of the lower end
of the back leg allows the whole arrangement to assume the position
shown in fig. 7, so that a load can be taken out of a vessel and
deposited on a quay wall. The same effect can be produced by
shortening the back leg by a screw placed in the direction of its
length. Sheer legs are generally built in very large sizes, and their
use is practically confined to marine work.

Another type of fixed crane is the "Fairbairn" crane, shown in fig. 8.
Here the jib, superstructure and post are all united in one piece,
which revolves in a foundation well, being supported at the bottom by
a toe-step and near the ground level by horizontal rollers. This type
of crane used to be in great favour, in consequence of the great
clearance it gives under the jib, but it is expensive and requires
very heavy foundations.

The so-called "hammer-headed" crane (fig. 9) consists of a steel
braced tower, on which revolves a large horizontal double cantilever;
the forward part of this cantilever or jib carries the lifting crab,
and the jib is extended backwards in order to form a support for the
machinery and counter-balance. Besides the motions of lifting and
revolving, there is provided a so-called "racking" motion, by which
the lifting crab, with the load suspended, can be moved in and out
along the jib without altering the level of the load. Such horizontal
movement of the load is a marked feature of later crane design; it
first became prominent in the so-called "Titan" cranes, mentioned
below (fig. 14). Hammer-headed cranes are generally constructed in
large sizes, up to 200 tons.

Another type of fixed revolving crane is the foundry or smithy crane
(fig. 10). It has the horizontal racking motion mentioned above, and
revolves either on upper and lower pivots supported by the structure
of the workshop, or on a fixed pillar secured to a heavy foundation.
The type is often used in foundries, or to serve heavy hammers in a
smithy, whence the name.

Portable cranes.

Portable cranes are of many kinds. Obviously, nearly every kind of
crane can be made portable by mounting it on a carriage, fitted with
wheels; it is even not unusual to make the Scottish derrick portable
by using three trucks, one under the mast, and the others under the
two back legs.

Fig. 11 represents a portable steam jib crane; it contains the same
elements as the fixed crane (fig. 4), but the foundation bed is
mounted on a truck which is carried on railway or road wheels. With
portable cranes means must be provided to ensure the requisite
stability against overturning; this is done by weighting the tail of
the revolving part with heavy weights, and in steam cranes the boiler
is so placed as also to form part of the counterbalance. Where the
rail-gauge is narrow and great weight is not desired, blocking girders
are provided across the under side of the truck; these are arranged so
that, by means of wedges or screws, they can be made to increase the
base. In connexion with the stability of portable cranes, it may be
mentioned that accidents more often arise from overturning backwards
than forwards. In the latter case the overturning tendency begins as
soon as the load leaves the ground, but ceases as soon as the load
again touches the ground and thus relieves the crane of the extra
weight, whereas overturning backwards is caused either by the reaction
of a chain breaking or by excessive counterweight. When portable
cranes are fitted with springs and axle-boxes, drawgear and buffers,
so that they can be coupled to an ordinary railway train, they are
called "breakdown" or "wrecking" cranes.

Dock-side jib cranes for working general cargo are almost always made
portable, in order to enable them to be placed in correct position in
regard to the hatchways of the vessels which they serve. Fig. 12 shows
an ordinary hydraulic dock-side jib crane. This type is usually fitted
with a very high jib, so as to lift goods in and out of high-sided
vessels. The hydraulic lifting cylinders are placed inside the
revolving steel mast or post, and the cabin for the driver is arranged
high up in the front of the post, so as to give a good view of the
work. The pressure is conveyed to the crane by means of jointed
"walking" pipes, or flexible hose, connected to hydrants placed at
regular intervals along the quay. It is often very desirable to have
the quay space as little obstructed by the cranes as possible, so as
not to interfere with railway traffic; this has led to the
introduction of cranes mounted on high trucks or gantries, sometimes
also called "portal" cranes. Where warehouses or station buildings run
parallel to the quay line, the high truck is often extended, so as to
span the whole quay; on one side the "long leg" runs on a rail at the
quay edge, and on the other the "short leg" runs on a runway placed on
the building. Cranes of this type are called "half-portal" cranes.
Fig. 13 shows an electric crane of this class. They give the minimum
of interference with quay space and have rapidly come into favour.
Where the face of the warehouse is sufficiently close to the water to
permit of the crane rope plumbing the hatches without requiring a jib
of excessive radius, it is a very convenient plan to place the whole
crane on the warehouse roof.

A special form of jib crane, designed to meet a particular purpose, is
the "Titan" (fig. 14) largely used in the construction of piers and
breakwaters. It contains all the essential elements of the
hammer-headed crane, of which it may be considered to be the parent;
in fact, the only essential difference is that the Titan is portable
and the hammer-head crane fixed. The Titan was the first type of large
portable crane in which full use was made of a truly horizontal
movement of the load; for the purpose for which the type is designed,
viz. setting concrete blocks in courses, this motion is almost a
necessity.

Non-revolving cranes.

As types of non-revolving cranes, fig. 15 shows an overhead traveller
worked by hand, and fig. 16 a somewhat similar machine worked by
electric power. The principal component parts of a traveller are the
main cross girders forming the _bridge_, the two _end carriages_ on
which the bridge rests, the _running wheels_ which enable the end
carriages to travel on the longitudinal gantry girders or _runway_,
and the _crab_ or _jenny_, which carries the hoisting mechanism, and
moves across the span on rails placed on the bridge girders. There are
numerous and important variations of these two types, but the above
contain the elements out of which most cranes of the class are built.

One variation is illustrated in fig. 17, and is called a "Goliath" or
"Wellington." It is practically a traveller mounted on high legs, so
as to permit of its being travelled on rails placed on the ground
level, instead of on an elevated gantry. Of other variations and
combinations of types, fig. 18 shows a modern design of crane intended
to command the maximum of yard space, and having some of the
characteristics both of the Goliath and of the revolving jib crane,
and fig. 19 depicts a combination of a traveller and a hanging jib
crane.

Transporters.

When the cross traverse motion of a traveller crab is suppressed, and
the longitudinal travelling motion is increased in importance we come
to a type of crane, the use of which is rapidly increasing; it goes by
the name of "transporter." Transporters can only move the load to any
point on a vertical surface (generally a plane surface); they have a
lifting motion and a movement of translation. They are of two kinds:
(1) those in which the motive power and lifting gear are
self-contained on the crab; and (2) those in which the motive power is
placed in a fixed position. A transporter of the first class is shown
in fig. 20. From the lower flange of a suspended runway, made of a
single I section, run wheels, from the axles of which the transporter
is suspended. The latter consists of a framework carrying the hoisting
barrel, with its driving motor and gearing, and a travelling motor,
which is geared to the running wheels in such a manner as to be able
to propel the whole machine; a seat is provided for the driver who
manipulates the controllers. A transporter of this kind, when fitted
with a grab, is a very efficient machine for taking coal from barges
and depositing it in a coal store.

In the other class of transporter the load is not usually moved
through such long distances. It consists essentially of a jib made of
single I-sections, and supported by tie-rods (fig. 21), the load to be
lifted being suspended from a small travelling carriage which runs on
the lower flange. The lifting gear is located in any convenient fixed
position. In order that only one motor may be used, and also that the
load may be lifted by a single part of rope, various devices have been
invented. The jib is usually inclined, so as to enable the travel to
be performed by gravity in one direction, and the object of the
transporter mechanism is to ensure that pulling in or slacking out the
lifting rope shall perform the cycle of operations in the following
order:--Supposing the load is ready to be lifted out of a vessel on to
a quay, the pull of the lifting rope raises the load, the travelling
jenny being meanwhile locked in position. On arriving at a certain
height the lift ceases and the jenny is released, and by the continued
pull of the rope, it runs up the jib; on arriving at an adjustable
stop, the jenny is again locked, and the load can be lowered out; the
hook can then be raised, when the jenny is automatically unlocked, and
on paying out the rope the jenny gravitates to its first position,
when the load is lowered and the cycle repeated. The jibs of
transporters are often made to slide forward, or lift up, so as to be
out of the way when not in use. Transporters are largely used for
dealing with general cargo between vessels and warehouses, and also
for coaling vessels; they have a great advantage in not interfering
with the rigging of vessels.

Nearly all recent advances in crane design are the result of the
introduction of the electric motor. It is now possible to apply motive
power exactly where it is wanted, and to do so economically, so that
the crane designer has a perfectly free hand in adding the various
motions required by the special circumstances of each case.

The literature which deals specially with cranes is not a large one,
but there are some good German text-books on the subject, amongst
which may be mentioned _Die Hebezeuge_ by Ernst (4th ed., Berlin,
1903), and _Cranes_, by Anton Bottcher, translated with additions by
A. Tolhausen (London, 1908). (W. P.*)

CRANIOMETRY. The application of precise methods of measurement marks a definite phase in the development of most branches of modern science, and thus craniometry, a comprehensive expression for all methods of measuring the skull (cranium), provides a striking landmark in the progress of anthropological studies. The origin of craniometry appears to be twofold. Certain artists made measurements of heads and skulls with a view to attaining greater accuracy in their representation of those parts of the human frame. Bernard de Palissy and A. Durer may be mentioned as pioneers in such researches. Again, it is clearly shown in the literature of this subject, that anatomists were led to employ methods of measurement in their study of the human skull. The determining cause of this improvement in method is curious, for it appeared at the end of a famous anatomical controversy of the later middle ages, namely the dispute as to whether the Galenic anatomy was based on the study of the human body or upon those of apes. In the description of the dissection of a chimpanzee (in 1680) Tyson explains that the measurements he made of the skull of that animal were devised with a view to exhibiting the difference between this and the human skull.

The artists did not carry their researches very far. The anatomists on the contrary continued to make measurements, and in 1764 Daubenton published a noteworthy contribution to craniometry. Six years later, Pieter Camper, distinguished both as an artist and as an anatomist, published some lectures containing an account of his craniometrical methods, and these may be fairly claimed as having laid the foundation of all subsequent work. That work has been described above as anthropological, but as the studies thus defined are very varied in extent, it is necessary to consider the subdivisions into which they naturally fall.

In the first place (and omitting further reference to the contributions of artists), it has been explained that the measurements were first made with a view to elucidating the comparison of the skulls of men with those of other animals. This wide comparison constitutes the first subdivision of craniometric studies. And craniometric methods have rendered the results of comparison much more clear and comprehensible than was formerly the case. It is further remarkable that among the first measurements employed angular determinations occur, and indeed the name of Camper is chiefly perpetuated in anthropological literature by the "facial angle" invented by that artist-anatomist (fig. 1). It appears impossible to improve on the simple terms in which Camper describes the general results of the employment of this angle for comparative purposes, as will appear from the following brief extract from the translation of the original work: "The two extremities of the facial line are from 70 to 80 degrees from the negro to the Grecian antique: make it under 70, and you describe an ourang or an ape: lessen it still more, and you have the head of a dog. Increase the minimum, and you form a fowl, a snipe for example, the facial line of which is nearly parallel with the horizon." (Camper's Works, p. 42, translated by Cogan, 1821.)

In the 19th century the names of notable contributors to the literature of craniometry quickly increase in number; while it is impossible to analyse each contribution, or even record a complete list of the names of the authors, it must be added that for the purposes of far-reaching comparisons of the lower animals with mankind, craniometric methods were used by P. P. Broca in France and by T. H. Huxley (figs. 2 and 3) in England, with such genius and success as have not yet been surpassed.

The second division of craniometric studies includes those in which the skulls of the higher and lower races of mankind are compared. And in this domain, the advent of accurate numerical methods of recording observations brought about great advances. In describing the facial angle, it will be seen that the modern European, the Greek of classical antiquity and the Negro are compared. Thus it is that Camper's name appears as that of a pioneer in this second main division of the subject. Broca and Huxley cultivated similar comparative racial fields of research, but to these names that of Anders Retzius of Stockholm must be added here. The chief claim of Retzius to distinction rests on the merits of his system of comparing various dimensions of the skull, and of a classification based on such comparisons. These indices will be further defined below. It is convenient to mention here that the first aim of all these investigators was to obtain from the skull reliable data having reference to the conformation or size of the brain once contained within it. Only in later days did the tendency to overlook this, the fundamental aim and end of craniometry, make its appearance; such nevertheless was the case, much to the detriment of craniometric science, which for a time seems to have become purely empirical.

The third subdivision of craniometric researches is one in which the field of comparison is still further narrowed. For herein the various sub-racial types such as the dark and fair Europeans are brought together for the purposes of comparison or contrast. But although the range of research is thus narrowed and restricted, the guiding principles and the methods remain unchanged. In this department of craniometry, Anders Retzius has gained the foremost place among the pioneers of research. Retzius's name is, as already mentioned, associated not with any particular angle or angular measurement, but rather with a method of expressing as a formula two cranial dimensions which have been measured and which are to be compared. Thus for instance one skull may be so proportioned that its greatest width measures 75% of its greatest length (i.e. its width is to its length as three to four).

FIG. 4.--Top view of skulls. (A) Negro, index 70, dolichocephalic; (B) European, index 80, mesaticephalic; (C) Samoyed, index 85, brachycephalic.]

This ratio (of 75%) is termed the cephalic or breadth-index, which in such an instance would be described as equal to 75. A skull providing a breadth-index of 75 will naturally possess very different proportions from another which provides a corresponding index equal to 85. And in fact this particular index in human skulls varies from about 58 to 90 in undistorted examples (fig. 4). Such is the general scheme of Retzius's system of classification of skulls by means of indices, and one of his earliest applications of the method was to the inhabitants of Sweden. One striking result was to exhibit a most marked contrast in respect of the breadth-index of the skull, between the Lapps and their Scandinavian neighbours, and thus a craniometric difference was added to the list of characters (such as stature, hair-colour and complexion) whereby these two types were already distinguished. Since the publication of Retzius's studies, the cephalic or breadth-index of the skull has retained a premier position among its almost innumerable successors, though it is of historical interest to note that, while Retzius had undoubtedly devised the method of comparing "breadth-indices," he always qualified the results of its use by reference to other data. These qualifications were overlooked by the immediate successors of Retzius, much to the disadvantage of craniometry. In addition to the researches on the skull forms of Lapps and Swedes, others dealing with the comparison of Finns and Swedes (by Retzius) as well as the investigation of the form of skull in Basques and Guanches (by Broca) possess historic interest.

Thus far little or nothing has been said with regard to instruments. Camper devised a four-sided open frame with cross-wires, through which skulls were viewed and by means of which accurate drawings could be projected on to paper. The methods of Retzius as here described require the aid of callipers of various sorts, and such instruments were quickly devised and applied to the special needs of the case. Such instruments are still in use, and two forms of simple craniometer are shown in the accompanying illustrations (figs. 5 and 6). For the more accurate comparison required in the study of various European types, delicate instruments for measuring angles were invented by Anthelme in Paris (1836) and John Grattan in Belfast (1853). These instruments enabled the observer to transmit to the plane surface of a sheet of drawing paper a correct tracing of the contour of the specimen under investigation. A further modification was devised by the talented Dr Busk in the year 1861, and since that date the number and forms of these instruments have been greatly multiplied. With reference to contributors to the advance of knowledge in this particular department of craniometry, there should be added to the foregoing names those of Huxley, Sir W. H. Flower and Sir W. Turner in England, J. L. A. de Quatrefages in France, J. C. G. Lucae and H. Welcker in Germany. Moreover, the methods have also been multiplied, so that in addition to angular and linear measurements, those of the capacity or cubical contents of the cranium and those of the curvature of its surface demand reference. The masterly work of Cleland claims special mention in this connexion. And finally while two dimensions are combined in the cephalic index of Retzius, the combination of three dimensions (in a formula called a modulus) distinguishes some recent work, although the employment of the modulus is actually a return to a system devised in 1859 by Karl E. von Baer.

The fourth subdivision of craniometry is closely allied to that which has just been described, and it deals with the comparison of the prehistoric and the recent types of mankind. The methods are exactly similar to those employed in the comparison of living races; but in some particular instances where the prehistoric individual is represented only by a comparatively minute portion of the skull, some special modifications of the usual procedures have been necessitated. In this field the works of W. His and L. Rutimeyer on the prehistoric races of Switzerland, those of Ecker (South Germany), of Broca in France, of Thurnam and Davis in England, must be cited. G. Schwalbe, Kramberger, W. J. Sollas and H. Klaatsch are the most recent contributors to this department of craniometry.

Thus the complexity of craniometric studies has inevitably increased. In the hands of von Torok of Budapest, as in those of M. Benedikt of Vienna at an earlier date, the number of measurements regarded as necessary for the complete "diagnosis" of a skull has reached a colossal total. Of the trend and progress of craniometry at the present day, three particular developments are noteworthy. First come the attempts made at various times to co-ordinate the systems of measurements so as to ensure uniformity among all observers; of these attempts two, viz. that of the German anthropologists at Frankfort in 1882 (figs. 7 and 8), and that of the Anthropometric Committee of the British Association (1906) seem to require at least a record. In the second place, the application of the methods of statistical science in dealing with large numbers of craniometric data has been richly rewarded in Prof. Karl Pearson's hands. Thirdly, and in connexion with such methods, there may be mentioned the extension of these systems of measurement, and of the methods of dealing with them on statistical principles, to the study of large numbers of the skulls of domestic and feral animals, such as white rats or the varieties of the horse. And lastly no account of craniometry would be complete without mention of the revolt, headed by the Italian anthropologist Sergi, against metrical methods of all kinds. It cannot, however, be alleged that the substitutes offered by the adherents of Sergi's principles encourage others to forsake the more orthodox numerical methods.

LITERATURE.--Tyson, _The Anatomy of a Pygmie_ (London, 1699);
Daubenton, "Sur la difference de la situation du tron occipital dans
l'homme et dans les animaux," _Comptes rendus de l'academie des
sciences_ (Paris, 1764); Camper, _Works_ (1770, translated by Cogan,
1821); Broca, _Memoires_ (1862 and following years); Huxley, _Journal
of Anatomy and Physiology_, vol. 1 (1867); Retzius, _Uber die
Schadelformen der Nordbewohner_ (Stockholm, 1842); Anthelme,
_Physiologie de la pensee_ (Paris, 1836); Grattan, _Ulster Journal of
Archaeology_, vol. 1 (1853); Busk, "A System of Craniometry,"
_Transactions of the Ethnological Society_ (1861); Flower, Catalogue
of the Hunterian Museum, _Osteology_, part 1 (London, 1879); Turner,
"'Challenger' Reports," _Zoology_, vol. x. pt. 29, "Human Crania"
(1884); de Quatrefages, _Crania ethnica_ (Paris, 1873); Lucae,
_Architectur des menschlichen Schadels_ (Frankfort, 1855); Welcker,
_Bau und Wachsthum des menschlichen Schadels_ (1862); Cleland, "An
Inquiry into the Variations of the Human Skull," _Phil. Trans. Roy.
Society_ (1870), vol. 160, pp. 117 et seq.; von Baer, "Crania
selecta," Academie imperiale des sciences de S. Petersbourg (1859);
His and Rutimeyer, _Crania Helvetica_ (Basel, 1866); Ecker, _Crania
Germaniae meridionalis_ (1865); Thurnam and Davis, _Crania
Britannica_; von Torok, _Craniometrie_ (Stuttgart, 1890); Benedikt,
_Manuel technique et pratique d'anthropometrie cranio-cephalique_
(Paris, 1889); Pearson, _Biometrika_, from vol. 1 (in 1902) onwards;
Sergi, "The Varieties of the Human Species," English translation,
Smithsonian Institution (Washington, 1894); Schwalbe, "Der
Neanderthalschadel," _Bonner Jahrbucher_, Heft 106; also _Sonderheft
der Zeitschrift fur Morphologie und Anthropologie_; Kramberger, _Der
palaolithische Mensch von Krapina_ (Nagele, Stuttgart, 1901); Sollas,
"The Cranial Characters of the Neanderthal Race," _Phil. Transactions
of the Royal Society_, vol. 199, Series B, p. 298, 1908; Klaatsch,
"Bericht uber einen anthropologischen Streifzug nach London,"
_Zeitschrift fur Ethnologie_, Heft 6, 1903, p. 875.

_Handbooks._--Topinard, _Elements d'anthropologie generale_ (Paris,
1885); Schmidt, _Anthropologische Methoden_ (Leipzig, 1888);
Duckworth, _Morphology and Anthropology_ (Cambridge, 1904).

_Journals._--_Bulletins de la Societe d'Anthropologie de Paris_,
_Journal of the Royal Anthropological Institute of Great Britain and
Ireland_, _Archiv fur Anthropologie_, _Zeitschrift fur Morphologie und
Anthropologie_. (W. L. H. D.)

CRANK, a word of somewhat obscure etymology, probably connected with a root meaning "crooked," and appearing in the Ger. _krank_, ill, a figurative use of the original word; among other words in English containing the same original meaning are "cringe" and "crinkle." In mechanics, a crank is a device by which reciprocating motion is converted into circular motion or vice versa, consisting of a _crank-arm_, one end of which is fastened rigidly at right angles to the rotating shaft or axis, while the other end bears a _crank-pin_, projecting from it at right angles and parallel to the shaft. When the reciprocating part of a machine, as the piston and piston-rod of a steam engine, is linked to this crank by a _crank-rod_ or _connecting rod_, one end of which works on the crank-pin and the other on a pin in the end of the reciprocating part, the to-and-fro motion of the latter imparts a circular motion to the shaft and vice versa. The crank, instead of being made up as described above, may be formed by bending the shaft to the required shape, as sometimes in the handle of a winch. A _bell-crank_, so called because of its use in bell-hanging to change the direction of motion of the wires from horizontal to vertical or vice versa, consists of two arms rigidly connected at an angle, say of 90 deg., to each other and pivoted on a pin placed at the point of junction.

Crank is also the name given to a labour machine used in prisons as a means of punishment (see TREAD-MILL). Other uses of the word, connected with the primary meaning, are for a crooked path, a crevice or chink; and a freakish turn of thought or speech, as in Milton's phrase "quips and cranks." It is also used as a slang expression, American in origin, for a harmless lunatic, or a faddist, whose enthusiasm for some one idea or hobby becomes a monomania. "Crank" or "crank-sided" is a nautical term used of a ship which by reason of her build or from want of balance is liable to overturn. This strictly nautical sense is often confused with "crank" or "cranky," that is, rickety or shaky, probably derived direct from the German _krank_, weak or ill.

CRANMER, THOMAS (1489-1556), archbishop of Canterbury, born at Aslacton or Aslockton in Nottinghamshire on the 2nd of July 1489, was the second son of Thomas Cranmer and of his wife Anne Hatfield. He received his early education, according to Morice his secretary, from "a marvellous severe and cruel schoolmaster," whose discipline must have been severe indeed to deserve this special mention in an age when no schoolmaster bore the rod in vain. The same authority tells us that he was initiated by his father in those field sports, such as hunting and hawking, which formed one of his recreations in after life. To early training he also owed the skilful horsemanship for which he was conspicuous. At the age of fourteen he was sent by his mother, who had in 1501 become a widow, to Cambridge. Little is known with certainty of his university career beyond the facts that he became a fellow of Jesus College in 1510 or 1511, that he had soon after to vacate his fellowship, owing to his marriage to "Black Joan," a relative of the landlady of the Dolphin Inn, and that he was reinstated in it on the death of his wife, which occurred in childbirth before the lapse of the year of grace allowed by the statutes. During the brief period of his married life he held the appointment of lecturer at Buckingham Hall, now Magdalene College. The fact of his marrying would seem to show that he did not at the time intend to enter the church; possibly the death of his wife caused him to qualify for holy orders. He was ordained in 1523, and soon after he took his doctor's degree in divinity. According to Strype, he was invited about this time to become a fellow of the college founded by Cardinal Wolsey at Oxford; but Dean Hook shows that there is some reason to doubt this. If the offer was made, it was declined, and Cranmer continued at Cambridge filling the offices of lecturer in divinity at his own college and of public examiner in divinity to the university. It is interesting, in view of his later efforts to spread the knowledge of the Bible among the people, to know that in the capacity of examiner he insisted on a thorough acquaintance with the Holy Scriptures, and rejected several candidates who were deficient in this qualification.