The pyrazolidines are tetrahydropyrazoles. The N-phenyl derivative, from sodium phenylhydrazine and trim ethylene bromide, is an oil which readily oxidizes to phenylpyrazoline on exposure. The corresponding keto-derivatives, or pyrazolidones, are produced by the action of hydra zines on the B-haloid acids or aB-olefine dicarboxylic acids. Isomeric compounds may arise here when phenylhydrazine is used, the keto-group takin either the 3 or 5 position; thus with /S-iodopropionic acid 1-piienylpyrazolidoneis formed, whilst potassium /3-iodopropionate gives the 3-compound. Isomers of this type may be distinguished by the fact that the pyrazolidone-5 compounds are basic, whilst the 3~compounds are acidic. The simplest member of the series, pyrazolidone-5, is a liquid which is formed by the action of hydrazine on acrylic acid. The 3-5-pyrazolidones are the cyclic hydrazides of the malonic acid series.
Thiopyrazoles have been obtained by A. Michaelis (/inn., 1904, 331, p. 197; Bef., I?O4, 37, p. 2774) by the action of an aqueous or alcoholic solution o the methyl chloride or iodide of phenylmethylchlorpyrazole on a solution of an alkaline hydro sulphide into which carbon bi sulphide has been passed; or by the action of sodium thiosulphate on antipyrine hydrochloride or a similar compound. The simplest member of the group is probably to be represented as
HC; C(SH) Hzc-CS
N'C5H5 OI' l N'C6H5.
CH3-C=N / CH3-C =N
PYRENE, C,6H10, a hydrocarbon found together with chrysene in the last portion of the coal tar distillate, and also in " Stupp " fat.
The crude solid product from the tar distillate is digested with carbon bi sulphide to dissolve the pyrene, the solution filtered and the solvent evaporated. The residue is dissolved in alcohol and to the cold saturated solution a cold alcoholic solution of picric acid is added. The picrate so formed is then decomposed by ammonia. On its separation from " Stupp " fat see E. Bamber er and M. Philip, Ann., 1887, 240, p. 161. It crystallizes in monochnic tables which melt at 148-149° C. Chromic acid oxidizes it to pyrene quinone, CNHBOZ, and pyrenic acid, Cu=, H18O¢. The picrate, which is easily soluble in benzene, crystallizes in long red needles melting at 222 When heated with hydriodic acid and phosphorus to 200° C. it yields a hexahydride. It has been obtained synthetically by M. Freund and H. Michaels (Ber., 1897, 30, p. 1383) by distilling thebenol over zinc dust in a stream of hydrogen, or by the action of hydriodic acid and phosphorus at 220° C. on thebenol
PYRENEES [Span. Pirinéos, Fr. Pyrénées], a range of mountains in south-west Europe, separating the Iberian Peninsula from France, and extending for about 240 m., from the Bay of Biscay to Cape Creus, or, if only the main crest of the range be considered, to Cape Cerbére, on the Mediterranean Sea. For the most part the main crest constitutes the Franco-Spanish frontier; the principal exception to this rule is formed by the valley of Aran, which belongs orographically to France but politically to Spain. The Pyrenees are conventionally divided into
three sections, the central, the Atlantic or western, and the eastern. The central Pyrenees extend eastward from the Port de Canfranc to the valley of Aran, and include the highest summits of the whole chain, Aneto or Pic de Néthou (11,168 ft.), in the Maladetta ridge, Posets (11,047 ft.), and Mont Perdu or Monte Perdido (10,997 ft.). In the Atlantic Pyrenees the average altitude gradually diminishes westward; while in the eastern Pyrenees, with the exception of one break at the eastern extremity of the Pyrénées Ariégeoises, the mean elevation is maintained with remarkable uniformity, till at last a rather sudden decline occurs in the portion of the chain known as the Alberes. This threefold division is only valid so far as the elevation of the Pyrenean chain is concerned, and does not accurately represent its geological structure or general configuration. The careful examination of the chain by members of the English and French Alpine Clubs has since 1880 considerably modified the views held with respect to its general character; the southern versant, formerly regarded as inferior in area, has been proved to be the more important of the two. It has been recognized, as shown in the maps of MM. Schrader, de St Sand and Wallon, that, taken as a whole, the range must be regarded, not as formed on the analogy of a fern-frond or fish-bone, with the lateral ridges running down to the two opposite plains, but rather as a swelling of the earth's crust, the culminating portion of which is composed of a series of primitive chains, which do not coincide with the watershed, but cross it obliquely, as if the ground had experienced a sidewise thrust at the time when the earth's crust was ridged up into the long chain under the influence of contraction. Both the orderly arrangement of these diagonal chains and the agreement which exists between the tectonic and geological phenomena are well shown in the geological and hypsometrical maps published in the Annuaire du Club Alpin français for 1891 and 1892 by MM. Schrader and de Margerie. The primitive formations of the range, of which little beyond the French portions had previously been studied, are shown to be almost all continued diagonally on the Spanish side, and the central ridge thus presents the appearance of a series of wrinkles with an inclination (from north-west to south-east) greater than that of the chain as a whole. Other less pronounced wrinkles run from south-west to north-east and intersect the former series at certain points, so that it is by alternate digressions from one to the other series that the irregular crest of the Pyrenees acquires its general direction. Far from having impressed its own direction on the orientation of the chain at large, this crest is merely the resultant of secondary agencies by which the primitive mass has been eroded and lessened in bulk, and though its importance from a hydro graphic point of view is still considerable, its geological significance is practically nil.
Geology.—The Pyrenees are divided by E. de Margerie and F. Schrader into a number of longitudinal zones. The central zone consists of Primary rocks, together with great masses of granite. It forms most of the higher summits, but west of the Pic d'Anie it disappears beneath an unconformable covering of Cretaceous deposits. On the French side the central zone is followed by (1) the zone of Ariege, consisting of Lower Cretaceous and Jurassic beds, together with granitic masses; (2) the zone of the Petites Pyrénées, Upper Cretaceous and Eocene; and (3) the zone of the Corbiéres, consisting of Eocene and Primary rocks. On the Spanish side, from north to south, are (1) the zone of Mont Perdu, Upper Cretaceous and Eocene; (2) the zone of Aragon, Eocene; and (3) the zone of the Sierras, Trias, Cretaceous and Eocene. In France the zones are clearly defined only in the eastern part of the chain, while towards the west they merge into one another. In Spain, on the other hand, it is in the central part of the chain that the zones are most distinct. Although the number of zones recognized is the same on the two flanks, they do not correspond. The zone of the Corbiéres has no equivalent in Spain, while in France there is no definite zone of Eocene like that of Aragon. The zone of the Petites Pyrénées, however, is clearly homologous with that of the Sierras. On the northern side granitic masses occur in the zone of Ariege amongst the Jurassic and Lower Cretaceous beds. On the southern side they are not found except in the axial zone, and the Jurassic and Lower Cretaceous deposits are reduced to a narrow band. In spite of these differences between the two flanks, the structure is to some extent symmetrical. On the north the greater number of the over folds lean towards the north, while on the south they lean towards the south. Thus the chain shows the typical fan-structure which has long been recognized in the western Alps.
Since the publication of the maps by de Margerie and Schrader it has been shown that the phenomena of "recouvrement" play almost as large a part in the Pyrenees as in the Alps themselves. Large masses of rock have been brought upon nearly horizontal faults (thrust-planes) over the edges 'of either beds with which they originally had no connexion. In the region of Salies-du-Salat, for example, patches of Trias lie discordantly upon the edges of the Cretaceous and Tertiary beds. Several other similar cases
