PAR 



PARENCHY'MA. (Trapi<yxypa, Gr.paren- 

 chyme, Fr.) 



1. A spongy or porous substance 

 forming the bulk of some of the 

 viscera, as the parenchyma of the 

 liver, &c. 



2. In botany, a fine, transparent, 

 membranous tissue, lying imme- 

 diately beneath the epidermis of 

 plants; it is of a deep green 

 colour, very tender, and succulent. 

 When viewed with a microscope, 

 it seems to be composed of fibres 

 which cross each other in every 

 direction. In its simplest state, it 

 appears like a mass of globules or 

 vesicles, crowded together ; these, 

 from pressure, assume a six-sided, 

 or hexagonal figure. 



PARENCHY'MATOUS. Consisting of pa- 

 renchyma; spongy; porous. 



PA'EGASITE. The name given to a 

 variety of actinolite, from its being 

 found in the Isle of Pargas, in 

 Finland. Colour forms the princi- 

 pal difference between hornblende 

 and pargasite, the latter being 

 somewhat translucent and of a 

 lighter green, or more generally of 

 a bottle-green hue. 



PAEIE'TAL. (from paries, a wall, Lat.) 



1. The name given to certain bones 

 of the skull, from their serving as 

 walls to the brain. 



2. In botany, a term used to ex- 

 press an adhesion of some part to 

 the inner side of an organ ; as 

 when the seeds are attached to the 

 placenta, the latter are termed 

 parietal. 



PA'KTS BA'SIN. A large area, to 

 which the name of Paris Basin 

 has been given, about 180 miles 

 in length, from north-east to south- 

 west, and about ninety miles wide, 

 from east to west. The country 

 in which the capital of France is 

 situated, is perhaps the most re- 

 markable that has yet been obser- 

 ved, both from the succession of 

 different soils of which it is formed, 

 and from the extraordinary organic 



[ S41 ] PAR 



remains which it contains. Bones 

 of land animals, of which the 

 genera are entirely unknown, are 

 found in certain parts ; other bones 

 remarkable for their vast size, and 

 of which some of similar genera 

 exist only in distant countries, are 

 found scattered in the upper beds. 

 Millions of marine shells, which 

 alternate regularly with fresh-water 

 shells, compose the principal mass. 

 The strata composing the Paris 

 basin rest upon chalk, lying, as it 

 were, in a depression of the chalk. 

 The depth of these strata varies 

 from one to five hundred feet. 

 MM. Brongniart and Cuvier di- 

 vided the strata into the five 

 following formations, commencing 

 with the undermost. 1. First 

 fresh- water formation ; consisting 

 of plastic clay, lignite, and first 

 sandstone. 2. First marine for- 

 mation ; comprising the calcaire 

 grossier. 3. Second fresh- water 

 formation ; containing silicious 

 limestone, gypsum, with bones of 

 animals, and fresh-water marls. 

 4. Second marine formation ; con- 

 sisting of gypseous marine marls, 

 upper marine sands and sandstones, 

 and upper marine marls and lime- 

 stones. 5. Third fresh- water for- 

 mation ; containing silicious mill- 

 stone with shells, and upper fresh 

 water marls. Subsequent obser- 

 vations have proved that this 

 division, as well as many of the 

 views entertained by MM. Brong- 

 niart and Cuvier, is not in accor- 

 dance with facts with which they 

 were unacquainted, and much 

 modification of the above arrange- 

 ment has been the consequence. 

 The silicious limestone, with fresh 

 water and terrestrial shells and 

 plants, and the calcaire grossier, or 

 first marine formation, often al- 

 ternate, and are deemed by M. 

 Constant. Prevost to be contempo- 

 raneous formations ; and it is not 

 improbable that while the wateri 



