the part of the church above it was elevated and approached by flights of stairs, in order to give height to the crypt. The crypt is not common in churches built after the Norman period and when found in those of the Gothic period is usually much older than the structure above them. The position of a crypt is generally beneath the choir, but occasionally, as at Glasgow Cathedral, beneath the transept also. The largest crypt in England is that at Canterbury Cathedral. Crypts rarely occur as a feature of a parish church. The larger crypt at Glasgow Cathedral is entirely above ground and at one time was used by itself as a church. In Germany, these underground chapels are numerous

the ones at Göttingen, Strassburg and Naumberg are fine examples of architecture. The most remarkable crypt in Italy is that of Saint Mark's, Venice, which is in the shape of a Greek cross. Short columns support low arches on which the floor above rests. Other Italian crypts are at Brescia, Fiesole, Modena, Milan, Pavia, Verona, Florence; and a particularly fine one at Assisi, A good example of Norman crypt is to be seen at the church of the Holy Trinity at Caen, France. In this country there are notable crypts at Saint-Chapelle, Paris, and at Saint Gervase, Rouen. Later churches abolished the necessity for this form of chapel.

CRYPTIDINE, krip'ti-din (CHN), a base homologous with quinoline, obtained in the preparation of that body, and also found in the less volatile parts of coal-tar. Its boiling-point is about 525° F., but it has not yet been prepared perfectly free from its lower homologues. It forms a double salt with platinum.

CRYPTO-CALVINISTS, name given to Melanchthon and those who agreed with him in wishing to unite the Lutherans and Calvinists, and especially in his supposed leaning toward the Calvinistic view of the Lord's Supper as shown in the difference between the original and the altered Augsburg Confession (q.v.). The former said "The body and blood of Christ are truly present in the Lord's Supper in the form of bread and wine and are there distributed and received by the communicant; therefore the opposite doctrine is rejected." In the latter the last clause is omitted. Luther did not approve the alteration, but tolerated Melanchthon's change of doctrine. Many, however, called him a Crypto-Calvinist. The truth seems to have been that he did not consider that either opinion was a sufficient bar to communion with Christ and therefore thought that both of them ought to be allowed. The controversy was becoming violent before his death, but afterward it broke out with great virulence, and continued with alternate success for 50 years, during which time frequent attempts were made to suppress the Calvinistic opinions by imprisoning their leading advocates and at last, in 1611, by the execution of Chancellor Nicolas Crell. The term has also been applied to the Missouri Lutherans because of their acceptance of the doctrine of unconditional election. Consult Richard, 'Philip Melanchthon' (New York 1898).

CRYPTOBRANCHIDE, krip"to-bran'kide (Gr. "with hidden gills"), a family of urodele Amphibia (q.v.) most nearly related, according to Cope, to the Amblystomide. There are no gills in the adult, but a single pore-like branchial fissure may persist on each side. Respiration is

pulmonary, but the inspirations occur only at intervals of several minutes. The vertebræ are biconcave but, like the remainder of the skeleton except the cartilaginous carpi and tarsi, are well ossified. There is no ethmoid bone, and the internal ear is separated from the brain by membrane only. A maxillary bone is developed, and teeth are borne on the margins of both jaws, as well as on the vomers, but not on the parasphenoid. The eyes are very small and devoid of lids; two pairs of limbs with four and five digits respectively are always present, and the tail is permanently provided with a fin. Two genera are known: Megalobatrachus, which has no branchial opening and contains only the giant salamander of eastern Asia, and Cryptobranchus, which contains the American hellbenders (q.v.).

CRYPTOGAMOUS PLANTS or CRYP. TOGAMS (from Gr. KрUTÓS, hidden + yáμos, marriage), all plants below the Phanerogams or flowering plants. The names were first used by Linnæus, who may thus have indicated his conviction that all plants possess sexuality, as most of them do. For a long time the vegetable kingdom was divided into two groups, as follows: (1) Phanerogamia, with stamens, ovules, seeds and embryos. (2) Cryptogamia, without stamens, ovules, seeds and embryos, and with spores. These distinctions, although long since acknowledged to be unscientific, are still maintained, especially in popular usage. The Cryptogams, instead of being a single group co-ordinate with the Phanerogams, include several such groups, namely, Algæ and Fungi (Thallophytes); Mossworts (Bryophytes); Fernworts (Pteridophytes). The Bryophytes and Pteridophytes are more closely related to one another and to the Phanerogams than to the very heterogeneous assemblage of the Thallophytes, the green members of which are known as algæ, while those without chlorophyll are mostly called fungi. For more detailed accounts of the cryptogams, see the articles the special groups just mentioned.

on

hidden beneath the coverts; the wings, which are very short and concave, have 10 primary and from 13 to 16 secondary quills; contour feathers are of the ordinary type found in flying birds, with the aftershaft rudimentary or absent. There are three long anterior toes with claws like a pheasant's, and the hallux is short and elevated, or, very rarely, absent; in fact the feet are of a strictly gallinaceous type. About 9 or 10 genera and 70 species are known, all but six of which are South American, occurring especially in Argentina and Brazil. See TINAMOUS.

CRYSTAL. The term crystal, derived from a Greek word signifying a hard crust, or more specifically ice, was applied by the Greeks at least 400 B.C. to a material which they supposed to be a hard, durable form of frozen water. This substance is the colorless, transparent variety of quartz still called rock crystal and this belief as to its nature lasted into the 16th century. The angular forms and the smooth, even surfaces of this substance were observed by the ancients, but were regarded either as accidents or as shapes "pleasing to the gods." The polyhedral solids obtained by the evaporation of solutions were also thought to be ice and therefore called crystal, although the error was earlier realized, for not only was crystallization recommended by Geber in the 8th century as a means of purification but the shapes of the crystals were to some extent recognized as characterizing the salt.

The secondary meaning of polyhedral form, solids bounded by plane faces, was therefore associated with the original meaning of frozen water and clear ice-like appearance and by a natural association of ideas other minerals, such as beryl, diamond, garnet and pyrite, which were observed to occur frequently in angular forms, were spoken of as crystal-like, or crystalline, and when, toward the close of the 18th century, the study of the shapes was first systematically undertaken, Romé de l'Isle called the new science crystallography (q.v.). That is, the word crystal no longer meant the transparent, ice-like substance, rock crystal, but an individual solid of any substance, whether transparent or opaque, provided this solid was bounded by plane faces at definite angles, and was formed as a result of the solidification of the substance.

This definition however is not fundamental and does not touch the essential nature of a crystal and while still held to by some authorities it can only be consistently maintained by the creation of some new term to include all individuals possessing that character which distinguishes crystals from all other bodies, namely, homogeneity of internal structure. The limitation to plane faced solids was due to the fact that external form was long the only character studied and even this character is a direct consequence of a regular internal structure, and, although it is a striking proof of this, it is often dependent upon comparatively minor conditions at the time of solidification.

All individual solids formed at the solidification of a substance, whether they are completely bounded by planes or partially bounded by planes or lack such boundaries and are of a shape determined by the space in which they formed exhibit equally well phenomena which prove the regular internal structure. For in

267

stance, characters such as transmission of light, the conductivity of heat, the cohesion, the elasticity or the rate of solubility are always alike in parallel directions, and, generally speaking, unlike in directions which are not parallel. Or if alike in more than one direction these directions will (whatever the boundary of the individual) bear the same relations.

The general usage now is to include the faceless and partially faced individuals, either with or without a modifying term, under the term crystal, one suggestion being to distinguish them as anhedral or faceless crystals, and the following definition of Fock expresses this tendency: A crystal is "a homogeneous solid body of definite chemical composition, whose physical properties are the same in parallel directions, but are generally different in directions not parallel." The outward sign is the form, but its destruction does not rob the fragments of their perfect internal structure, whereas the most perfect model is not a crystal, because it lacks the internal physical characteristics.

A further modification of the definition will be needed if the doubly refracting liquids described by Lehmann are admitted to be assemblages of liquid crystals. There is no definite limit between solid and liquid. In some of the softer solids one layer may be made to glide over another by pressure as in calcite and ice, other solid crystals are pliable, iodide of silver at 146° C. will flow like a thick liquid yet retain many crystal properties and certain organic substances which possess the mobility of oil or water and yet show double refraction dichroism, interference figures and even polyhedral form are difficult to exclude. The definitions thus far limit crystals to solids; whether this limit will be sufficiently removed to include the so-called "liquid crystals" is still in doubt.

The External Form of Crystals.-Although some differences between the shapes of crystals of different substances had been noticed and these differences utilized in descriptions of minerals and salts, the general belief, as late as the 16th century, was that the shapes in which any one substance occurred were neither constant nor related to each other.

In 1669 Nicolas Steno, a Danish anatomist, announced that the angles between corresponding faces of different quartz crystals were constant no matter how much the crystals varied in shape. This constancy of angles was stated by Guglielmini in 1704 to be general, in that every salt had its peculiar crystals, the angles of which were constant even when the crystals were imperfect and broken.

That in addition to the constancy of angles between corresponding faces there was an intimate relation between the very different shapes often assumed by crystals of the same substance was first shown clearly by Romé de l'Isle, who, continuing the method of Linnæus, measured and made wooden models of different crystals and in 1783 described over 400 regular forms. As a result of his comparisons de l'Isle found that differently shaped crystals of any one substance always formed a series and that all the members of such a series could be derived by "modifying" one so-called "primitive form," the shape and angles of which varied with the substance, by particular methods, such as replacing each edge by one plane or by two planes,

or each solid angle by one, three, four or six planes.

Réné Just Haüy, either as the result of an independent discovery or in view of the fact that Torbern Bergmann in 1773 had shown that calcite could be cleaved or broken into little sixfaced fragments with constant angles and that these rhombohedral fragments could be built together again into the different observed shapes of calcite, assumed this property of cleavage to be general and instead of the arbitrarily chosen primitive form of de l'Isle he chose for each substance a primitive form the faces of which were parallel to directions of cleavage, or if no cleavage was found or cleavage only in one direction, he assumed a shape determined by striations or other markings or by analogy between the shapes of the crystals of other substances which did show cleavage.

More important than this however he laid the foundation for the great law of "simple mathematical ratio" by showing that the angles made by the secondary planes were not arbitrary, but always fulfilled certain conditions, and were not simply grouped in the same way at each corresponding edge or angle but were at exactly those angles which would result if upon the primitive form little "integrant molecules" of shapes determined by cleavage were built up in successive layers, each successive layer regularly diminishing from the subtraction of one or more rows, always some simple rational number, never to his knowledge_exceeding four.

Professor Weiss of Berlin in 1809 discarded Hauy's hypothesis of decreted rows and substituted the conception of imaginary axes "around which the crystal is uniformly disposed." He divided all crystals into groups dependent upon the relative inclinations of the axes. The primitive forms of Hauy he constructed by planes intersecting all the axes or parallel to one or to two of them. If a primitive form cut three axes at distances a, b and c from the centre, then all secondary forms could be constructed by taking points along each of the axes at twice, three times and four times, etc., the lengths a, b and c, and constructing planes in the same way as before. That is, the intercepts of any secondary face in terms of a, b and c were rational, such as 2a: b: 3c or a: 3b: 2c.

Symmetry, or the repetition of equal angles or similarly grouped faces, was made a crystal character by de l'Isle in his statement, "Every face has an opposite parallel face." In any de l'Isle or Haüy series each form was derived by equivalent changes of each similar edge or angle of the primitive form, therefore without change of symmetry, that is "All crystals of any one substance are of the same grade of symmetry." Hessel in 1830, Gadolin in 1864, and von Lang in 1867 considered the possible varieties of symmetry of polyhedrons when limited by the law of rational parameters. Each obtained 32 types or classes.

It may be said then briefly that, with respect to external form, the crystals of any one substance will have the same symmetry, which will be one of the 32 types, that the angles between corresponding faces will be constant, and that the possible shapes will constitute a series in which the positions of the faces are not arbitrary, but fulfil certain conditions (the law of rational parameters).

The methods by which angles are measured

and symmetry symbols and constants determined are described in brief in the article on CRYSTALLOGRAPHY.

The Dependence of Physical Behavior upon Direction in Crystals as Evidence of Regular Internal Structure. The physical behavior of a crystal varies in the direction in which the test is applied. Like effects are obtained in directions which are parallel in the crystal and, generally, unlike effects are produced in directions not parallel, and like effects are obtained in directions symmetrically related in the crystal form. All this may be interpreted as similar molecular arrangement in directions giving like effects and differing arrangement in directions giving unlike effect.

These facts were suggested toward the close of the 17th century by the results of the studies of calcite made by Bartholin and Huyghens, which may be summed briefly as follows: A ray of light transmitted through calcite in any direction, except one, is split into two rays usually following different paths so that an object viewed through calcite appears double.

The divergence of these paths (roughly shown by the distance apart of the images) varies with the direction. In one direction, which is also the direction of the principal axis of geometric symmetry, there is single refraction only, and in all directions equally inclined to this direction of single refraction the double refraction (shown by the distance apart of the images) is the same.

If polarized light, in which the vibration direction is known, is transmitted through crystals, many proofs of the dependence of the effects upon the direction and upon symmetry can be obtained, the regularly varying indices of refraction, the vibration directions of the transmitted light, the differences in absorption and color in fact, by these effects the symmetry can be accurately judged.

Even with very primitive apparatus Brewster and others obtained before 1820 the so-called interference figures," color rings of various shapes crossed by dark bands, and Brewster was able to classify nearly all those substances to which Hauy had assigned "primitive forms" and to correct several errors in classification made by the latter. Furthermore, these results were obtained in particular crystallographic directions and the distribution of color and shape of the figures were symmetrical to the planes and axes of geometrical symmetry of the crystals.

A striking proof of the dependence of optical behavior upon direction and of a relation between this and crystalline form is shown when polarized light is transmitted through quartz crystals in the direction of the prism axis. In this direction and in this direction only in all such crystals the emerging ray is polarized in a different plane from the entering ray, or, as it is usually stated, quartz crystals rotate the plane of polarization a definite number of degrees, dependent upon the thickness. But when crystals of quartz which show the less common faces are examined it is seen by the arrangement of these faces that there are two sorts of crystals, the faces of which are relatively like the right and left hand, and Herschel and Brewster in 1821 showed that the plane of polarization was turned to the right by the one sort of quartz crystal and to the left by the other.

The dependence of physical behavior upon