have tended to bring them closer to one another, we still find that of the thirty-six chief orders three claim an origin from the caliph Abūbekr, whom the Sunnites honour, and the rest from ‘Alī, the idol of the Shī‘ites.[1] Mystic absorption in the being of God, with an increasing tendency to pantheism and ascetic practices, are the main scope of all Ṣūfīism, which is not necessarily confined to members of orders; indeed the secret practice of contemplation of the love of God and contempt of the world is sometimes viewed as specially meritorious. And so ultimately the word ṣūfī has come to denote all who have this religious direction, while those who follow the special rules of an order are known as dervishes (beggars, in Arabic fuqarā, sing. faqīr—names originally designating only the mendicant orders). In Persia at the present day a Ṣūfī is much the same as a freethinker.[2]
Bibliography.—The work of Shahrastānī (q.v.) on the Moslem sects: A. von Kremer, Geschichte der herrschenden Ideen des Islams (Leipzig, 1868); I. Goldziher, Muhammedanische Studien, vol. ii. (Halle, 1890); D. B. Macdonald, Muslim Theology (London, 1903); the Hidaya (trans. C. Hamilton, 2nd ed., London, 1870); N. B. E. Baillie, A Digest of Muhammadan Law (London, 1865); E. Sachau, Muhammadanisches Recht nach Schafiitischer Lehre (Stuttgart and Berlin, 1897); El-Bokhari, les traditions islamiques (trans. by Houdas and Marçais, Paris, 1903); Lane, An Account of the Manners and Customs of the Modern Egyptians (London, 1836). For the organization of the ‘ulemā in the Ottoman Empire during the middle ages see E. J. W. Gibb, A History of Ottoman Poetry, ii. 394 sqq. (London 1902).
SUNSHINE. As a meteorological element sunshine requires some conventional definition. There is uninterrupted continuance of gradation from the burning sunshine of a tropical noon to the pale luminosity that throws no shadow, but just identifies the position and shape of the sun through the thin cloud of northern skies.
The Campbell-Stokes Sunshine Recorder.—In the British Isles the sun is allowed to be its own timekeeper and the scorch of a specially prepared card used as the criterion for bright sunshine. The practice arose out of the use of the sunshine recorder which depends upon the scorching effect of a glass sphere in the sun's rays. The original form of the instrument was suggested by J. F. Campbell of Islay in 1857. He used a glass sphere within a hemispherical bowl of wood. The scorching of the wood along successive lines of the bowl as the sun alters its declination from solstice to solstice leaves a rugged monument of the duration and intensity of the sunshine during the half-year, but does not lend itself to numerical measurement. The design of a metal frame to carry movable cards and thus give a decipherable record of each day's sunshine is due to Sir G. G. Stokes. The excursions of the sun to the north and south of the equator are limited by the tropical circles, and the solar record on the hemispherical bowl will be confined within a belt 23° 27′ north and south of the plane through the centre parallel to the equator or perpendicular to the polar axis. Thus a belt 46° 54′ in angular width will be suitable for a sunshine recorder for any part of the world. Whatever place be chosen for the observation the same belt will do if it is set up perpendicular to the earth's polar axis. But there can be no record if the sun is below the horizon; hence any part of the belt projecting above the horizon is not only useless for recording but is liable to shadow a part of the belt where there might be a record. Hence to meet the requirements of a particular locality the belt as set up round the polar axis should be cut in two by a horizontal plane through the centre and the half projecting above the horizontal removed. Reversed it makes a half belt, exactly similar to what is left, and thus each complete belt is cut by a horizontal plane through the centre into two frames suitable for sunshine recorders for the particular locality.
Fig. 1.—Campbell-Stokes Sunshine Recorder.
.jpg)
Antarctic Sunshine Recorder, to carry 24-hour record.
.jpg)
Antarctic Sunshine Recorder, to carry 12-hour record.
The cutting of the belt may, of course, vary between the direct
transverse cut along the polar axis which gives a half-ring belt
to be set vertical in order to receive the record for a point on
the equator, and the cut perpendicular to the polar axis which
divides the belt into two similar rings suitable for recording the
sunshine at the poles. Clearly, when the belt is so cut that two
complete rings are formed, a continuous record of sunshine
throughout the twenty-four hours may be expected, so that for
the polar circles the cut will run diagonally between opposite
points of the extreme circles of the sun's records. As examples
of the cutting of the belt for different latitudes we may put side
by side the recorder as used in temperate latitudes (fig. 1) and
the special form designed in the Meteorological Office, London,
for use on the National Antarctic Expedition, 1901-1904 (fig. 2).
A belt cut for a particular latitude is serviceable for some 10°
on either side of that latitude if the cards are not trimmed too
must always be closely to the cutting of the belt. The belt
adjusted round the parallel to the polar axis. If the cut of the
belt is too oblique for the latitude of the place where it is exposed,
and the cards are cut strictly to the belt, the northern side of the
cut will be below the horizon and the southern side above it,
