parts of the body, are comparatively undeveloped, and the clear black, white and red (the last being due to a patch of papillose skin of that colour) of the head and neck are as yet indistinct. During this time they keep in the marshes, but as autumn approaches the different families unite by the rivers and lakes, and ultimately form the enormous bands which after much more trumpeting set out on their southward journey.
The crane’s power of uttering its sonorous and peculiar trumpet-like notes is commonly ascribed to the formation of its trachea, which on quitting the lower end of the neck passes backward between the branches of the furcula and is received into a hollow space formed by the bony walls of the carina or keel of the sternum. Herein it makes three turns, and then runs upwards and backwards to the lungs. The apparatus on the whole much resembles that found in the whooping swans (Cygnus musicus, C. buccinator and others), though differing in some not unimportant details; but at the same time somewhat similar convolutions of the trachea occur in other birds which do not possess, so far as is known, the faculty of trumpeting. The crane emits its notes both during flight and while on the ground. In the latter case the neck and bill are uplifted and the mouth kept open during the utterance of the blast, which may be often heard from birds in confinement, especially at the beginning of the year.
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. γέρανος, 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.
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
Classifica-
tion.
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.
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 costMotive
powers.
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 2¼ 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
