141 



OSMERUS. 



OTOHYS. 



142 



it crackles, loses water at 212, and melts without being discoloured ; 

 but on continuing the heat it decomposes, yielding ammonia. At 

 65 Fahr., 100 parts of water dissolve about 1'2 part; this solution 

 is scarcely at all acted upon by saline or metallic substances. The 

 solution slowly decomposes, exhaling a distinct ammoniacal odour aiid 

 becoming turbid. Alcohol and most acids also dissolve it. 

 OSMERUS. [SALMONID.E.] 



OSMIUM. [1'LATINUM.] 



OSMUNDA, a genus of Plants belonging to the natural order Fillces, 

 and to the sub-order Osmundaceas. It has clustered theca) arranged 

 in a branched spike terminating the frond. 



0. rcgalii, the Flowering Fern, has bipinnate fronds, pinnules oblong, 

 nearly entire, dilated, and slightly auricled at the base; the clusters 

 panicled, terminal This fern is a native of Great Britain in boggy 

 places, and often attains a height of from 1 to 8 feet. It is very 

 common in many parts of England, and especially on the lakes of 

 Killarney in Ireland. It is common throughout Europe, and a plant 

 of the same name is found in the United States. 



(Babington, Manual of British Botany; Newman, British Perm.) 



OSPREY. [FALCONUXE.] 



OSSEOUS BRECCIA. [OSSIFEBOCS BRECCIA.] 



OSSIFEROUS BRECCIA, OSSIFEROUS CAVERNS. The exist- 

 ence of Urge fissures And caverns in rocks is a fact known to miners 

 and quarrymen in all parts of the world ; that these cavities are 

 frequently filled with stalactitical sparry and earthy accumulations, 

 and sometimes with the bones of animals, is another fact on which 

 modern geologists have based a long train of ingenious inferences. 

 Fully to examine these facts and inferences would be to discuss one 

 of the most comprehensive and unsettled problems of geology. It is 

 possible however to present in a small compass the leading conside- 

 rations which belong to the subject. 



Great fissures and caverns, though not absolutely confined to lime- 

 atone rocks, are yet by far of most frequent occurrence in these deposits. 

 They are not common in all limestones, but have certain determinate 

 relations to their mass and the positions which they occupy. It is 

 peculiarly in thick masses of limestone (whether magnesiferous or 

 purely calcareous) that we find great caverns in England, Ireland, 

 France, Belgium, North Germany, the Tyrol, Cariothia, Italy, Greece, 

 North and South Africa, India, Australia, North and South America. 

 It is sometimes observed that great cavities abound in limestone rocks, 

 not so much at as near to points and lines where the ordinary position 

 of the strata is violently disturbed by great faults, and axes of elevation 

 and depression. Thus the numerous caverns of Derbyshire and York- 

 shire, and of the Mendip Hills, are situated in or near to situations of 

 violently-disrupted strata ; and by accumulating observations of this 

 nature we gradually come to perceive, in many cases, a real dependence 

 of the chasms in the rock on the fractures which have broken it. 



But there are few caverns or great fissures all whose features can 

 be thus explained. The disturbance has not so often produced the 

 caverns as the conditions necessary for their production. On the 

 contrary, in very many cases we perceive, even in caverns now dry, forms 

 of internal surface which mark the decomposing influence of air and 

 moisture, and the erosive power of running water. Through many of 

 them water now runs, through more of them it formerly ran, con- 

 ducted into these subterranean channels by the fractured condition of 

 the strata. The great caverns of the Peak at Castleton and Buxton 

 may be quoted as examples. Other caverns occur, nearly or entirely 

 exempt from the direct influence of fractures passing through them. 

 Such a case occurs at Kirkdole in Yorkshire ; a cave which has for 

 great lengths an even floor and roof, and is connected, not with faults 

 or axes of movement, but with great joints in the limestone. This 

 cave has been traversed by water conducted by these joints. Water 

 dropping, trickling, or running through the fissured limestone rocks, 

 dissolves (by the almost constant carbonic impregnation which it 

 derived from the atmosphere and decomposing vegetation) its calca- 

 reous channels, and transports away to the surface of the ground the 

 materials of petrifying springs, the tufaceous mounds of Matlock, and 

 the travertino of southern Europe. In certain classes of limestone 

 rocks there is reason to conjecture that the caverns have not been 

 occasioned by violent fractures, nor yet by the influence of joints, but 

 that they are a part of the original structure of a coral reef (hi which 

 cavities were left by the poly pean builders), or have been generated 

 by those chemical processes which we have as yet imperfectly traced 

 and classed as metamorphic effects. This may be the case in certain 

 magnesiferous (dolomitic) limestones in Derbyshire, Franconia, &c. 



In regard to the filling of these cavities, we must again, in a great 

 majority of instances, appeal to the action of water an inverse action, 

 new circumstances causing water to deposit where once it excavated ; 

 or an indirect action, occasioning new accidents. Stalactitical depositions 

 and many varieties of sparry accumulations, which are now happening 

 in caverns and fissure*, exemplify the former case ; and as an instance 

 of the latter, we may describe what is happening on a part of the 

 Yorkshire coast. Here the chalk is cavernous ; the caverns, connected 

 above with small fissures reaching to a mass of diluvial clay, pebbles, 

 &c., are continually enlarged by the waves and spray of the sea ; and 

 sometimes their roof, thus weakened, falls in, and the diluvial masses 

 from above pour down into the cave, but are soon removed by the 

 agitation of the tide. 



Another instance is of familiar occurrence in the mining districts of 

 the north of England, where limestone, more or leas cavernous and 

 fissured, is covered by shales or argillaceous loadstones. Near the 

 edge of these argillaceous beds many rather regular pits ( ( swallow- 

 holes') occur, through which the surface drainage reaches the lime- 

 stone, and carries into its cavities some of the materials which are 

 dislodged in its course. 



The geologist who takes into consideration the possible origin of 

 caverns in limestone from original hollows, the influence of joint- 

 fissures, and the effect of violent displacements and considers further 

 the various degrees and circumstances of their communication to the 

 surface, the various action of water within them, their level in relation 

 to that of the sea, and the nature of the strata or other matter super- 

 incumbent on the limestone will be at no loss to comprehend how 

 various, complicated, and interesting are the sparry and earthy contents 

 of subterranean cavities. These contents have in some cases fallen in, 

 so as to constitute confused heaps or masses of breccia ; in other cases 

 they have been drifted by water, and arranged into shallow and irre- 

 gular beds ; and in addition, certain matters have been dissolved, and 

 deposited in crystallised and stalagmitic forms. 



The occurrence of bones in these breccias, sediments, and stalag- 

 mitic incrustations, is sometimes to be explained by supposing them 

 to have fallen with the other materials of breccia, or to have been 

 drifted with sediments by water ; but in a considerable proportion of 

 the cages which have been examined there is no avoiding the conclusion 

 that animals retired by choice, or through fear, or were dragged by 

 violence into these cavities, and there have left their bones. This 

 conclusion, established by the sagacity of Buckland for the hyicua 

 caves of Kirkdale and Torquay, applies to the numerous bear caverns 

 of the Harz, Franconia, and Westphalia, and to some caves in Brazil 

 and Virginia. It is a conclusion of the highest importance in geology 

 and zoology. It assures us of the habitat of many extinct races or 

 quadrupeds, and thus furnishes authentic data for a survey of the 

 geographical distribution of Mammalia in one definite period of high 

 antiquity, under physical and climatal conditions of the globe much 

 different from what we now behold. Thus for instance we find 

 among the perished races of British quadrupeds the lion, hyscna, and 

 bear; the elephant, rhinoceros, and hippopotamus; the urus and 

 the elk. 



To allow of the introduction of these animals to Britain, we must 

 suppose this island joined to the continent; to allow of their long- 

 continued existence here (which the phenomena in Kirkdale cave 

 substantiate), we must suppose certain climatal and physical conditions 

 of the country, and certain habits of life among the animals. Migra- 

 tions may be supposed for the deer and the lion, but settled abodes 

 must be ascribed to the hyaena and perhaps to the Pachydermata. 

 The extinction of these animals requires other admissions. It is not 

 a local, but a general phenomenon, extending over a great part of the 

 northern zones of the world, and of such startling magnitude, as to 

 have suggested hypotheses of diluvial catastrophes and glacial periods 

 to geologists ; while zoologists may perhaps regard it as a great example 

 of the law of limited duration aud successive predominance, to which, 

 judging from the whole course of palicontological discovery, all the 

 races of the animal creation are made subject. 



(Cuvier, Ossemtns Fotile ; Buckland, Reliquia; DUumance ; Meyer, 

 Palteoiogica ; Owen, On Britith Fossil Mammalia, in Transactions of 

 the British Association; Mantell, Petrifactions and their Teachings; 

 and a variety of Memoirs by different authors in the Transactions and 

 Proceedings of the Qcoloyical Society of London.) 



OSSIFICATION. [BONE.] 



OSTRACE/E, or OSTREHXE, a family of Conchiferous Mollutca, 

 embracing, according to some authors, the following genera, Ostrea (to 

 which the common oyster belongs), Anomia, Placuna, Pecten, Lima, 

 Spondylui, and Plicatula. To these genera are sometimes added 

 (jryphaa, Exogyra, Carolia, Pododetmut, Placunamonia, and (Enigura. 

 Pecten is often regarded as the type of this family. [PECTINIDA] 



OSTRACION. [SCLERODERMI.] 



OSTRACODA. [BBANCHIOI-ODA,] 

 OSTREA. [PECTINID*.] 



OSTRICH. [STRUTHIONID.E-1 



OSTROCODA. [BRANCHIOFODA ; EXTOMOSTRACA.] 



OS'TRYA, a genus of Plants, the species of which are called Hop- 

 Hornbeams. They derive their English name from their inflorescence 

 consisting, in the female, of scales packed closely over each other so as 

 to resemble very much the head of a hop, and to its foliage being 

 similar to that of the hornbeam. Two species are known ; the one, 

 0. vulgaris, a native of the South of Europe ; the other, 0. Virgmica, 

 of the United States ; these are possibly mere varieties of each other. 

 They both form handsome deciduous trees, usually of small size, 

 but sometimes acquiring a height of 60 feet. (Loudon, Arboretum 

 Britannicum.) 



OTARIA. [PHOCIM:.] 



O'TILOPHES (Otilophi), Cuvier*s name for a group of Batrachian 

 Reptiles [AMPHIBIA], which have the muzzle angular, and the head 

 furnished on each side with a crest which extends over the parotid 

 portion. 



Itnna, margarilifera is an example (see cut, col. 143). It inhabits 

 Brazil, where, according to Seba, it is called Aquaqua. 



