W A T 



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WEN 



WA'TER-WORN. Worn away, rounded, 

 smoothed, by the action of running water. 

 WA'VED. Variegated ; undated. 



1. In botany, applied to the margins of 

 leaves, when bordered alternately with 

 numerous minute segments of circles and 

 angles. 



2. In entomology, applied to insects when 

 the margin of the body is marked with 

 a succession of arched incisions. 



WA'VELLITE. A rare mineral, first disco- j 

 vered in Devonshire by Dr. Wavell, and 

 named after him. Its colours are either pure 

 * white or white tinged with grey, green, or 

 yellow ; lustre silky. Specific gravity from 

 2'25 to 2' 70. It consists essentially of | 

 alumine, being composed of alumine 71*5, | 

 water 28*0, oxide of iron 0'5. Sometimes } 

 a trace of silex and lime is present. 



WEALD, (from wald, Germ, a wood.) The 

 name given to a valley, or tract of country, I 

 lying between the North and South Downs 

 of Kent and Sussex. 



WEALD-CLAY. A tenacious blue clay, con- i 

 taining subordinate beds of sandstone and ! 

 shelly limestone, with layers of septaria j 

 of argillaceous ironstone, forming the i 

 subsoil of the wealds of Sussex and Kent, | 

 and separating the Shanklin sand from the 

 central mass of the Hastings beds. Dr. 

 Mantell's Geology of the South-east o/j 

 England. 



WEA'LDEN FORMATION. > The term Weal- j 



WEALDEN STRATA. $ ^ en was SU S- ! 

 gested, as the most appropriate that could 

 be assigned to the strata of the Wealds of 

 Kent and Sussex, by J. P. S. Martin, j 

 Esq. of Pulborough. The Wealden for- ! 

 mation, group, or strata, have been sepa- 

 rated into three principal divisions. 



1. The Wealden clay, above described. 



2. The Hastings sands : grey, white, yel- 

 low, and reddish brown sands, and friable 

 sandstone, passing into limestone. 



3. The Purbeck beds, called also Ashburn- 

 ham beds, consisting of grey limestone, 

 alternating with blue clay and sandstone 

 shale. The whole of these are freshwater 

 or fluviatile deposits. Dr. Mantell may 

 be considered the great geological cham- 

 pion and hero of the Wealden, for to his 

 indefatigable exertions in that field, are 

 owing some of the most splendid disco- 

 veries in Palaeontology. Until the ap- 

 pearance of Dr. Mantell 's works on the 

 Geology of Sussex, the peculiar relations 

 of the sandstones and clays of the interior 

 of Kent, Sussex, and Hampshire, were 

 entirely misunderstood. No one sup- 

 posed that these immense strata were 

 altogether of a peculiar type, and inter- 

 polated amid the rest of the marine for- 

 mations, as a local freshwater deposit. 

 Prof. Phillips. 



It was not until the appearance of Dr. 



Mantell's illustrations of the Geology of 

 Sussex, that the full value of the evidence 

 which this district affords was made to 

 appear. In that excellent work the au- 

 thor clearly showed that the extraordinary 

 remains which he had discovered in the 

 beds of Tilgate Forest must have origi- 

 nated in a lake or estuary, and have been 

 the produce of a climate much warmer 

 than that which is now enjoyed in Eng- 

 land. Dr. Fitton. 



To the indefatigable and scientific re- 

 searches of Dr. Mantell we are indebted 

 for a knowledge of the true geological 

 characters of the Wealdean beds. Mr. 

 Bakewell. 



Dr. Mantell observes that the Wealden 

 may be considered as covering an area 

 200 miles in length, from west to east, 

 and 220 miles from north-west to south- 

 east, the total thickness averaging about 

 2000 feet. Of this series of deposits, 

 clays or argillaceous sediments, with 

 limestone almost wholly composed of 

 freshwater snail-shells, occupy the upper- 

 most place ; sand and sandstones, with 

 shales and lignite, prevail in the middle ; 

 while in the lowermost, argillaceous beds, 

 with shelly marbles or limestones, again 

 appear ; and, buried beneath the whole, 

 is a petrified forest, in which the trees are 

 still standing, and the vegetable mould 

 undisturbed. The organic remains of the 

 Wealden consist of leaves, stems, and 

 branches of plants of a tropical character ; 

 bones of enormous reptiles of extinct 

 genera, of crocodiles, turtles, flying rep- 

 tiles, and birds ; fishes of several genera 

 and species, and shells of a fluviatile 

 character. Not a vestige of the mamma- 

 lia has been discovered in the Wealden. 

 For a knowledge of that enormous reptile, 

 the Iguanodon, we are entirely indebted 

 to the indefatigable and scientific re- 

 searches of Dr. Mantell ; and for a most 

 interesting and elaborate detail of all 

 matters relating to the Wealden deposits 

 and their contents, the reader is referred 

 to Dr. Mantell's Geology of the South- 

 east of England and his Wonders of 

 Geology. 



WEDGE-SHAPED. In botany, applied to 

 leaves that are broad at the summit and 

 gradually taper toward the base. 

 WEIGHT OF THE ATMOSPHERE. The air 

 is an elastic fluid resisting pressure in 

 every direction, and is subject to the law 

 of gravitation. The pressure of the at- 

 mosphere is calculated to be about fifteen 

 pounds to every square inch, so that the 

 surface of the globe sustains a weight of 

 11,449,000,000 hundreds of millions of 

 pounds. Mrs. Somerville. 

 WE'NLOCK FORMATION. The lower forma- 

 tion of the upper Silurian rocks, compris- 



