108 LICHEN 



By the term lias, however, is ordinarily only understood the calcareous and argil- 

 laceous division, -which constitutes the lower section of the entire formation. 



In an economical point of view, it is of considerable value from its furnishing a 

 useful and durable stone, both for building and paving ; for the latter purpose it is 

 particularly suited, not only from the large dimensions of the flags it affords, but on 

 account of its occurrence in thin layers, which, in many cases, when required for 

 rough purposes only, are used in the state in which they are taken from the quarry, 

 without undergoing subsequent dressing. The lime furnished by the blue lias limestone 

 is also well known, and in great request, some of the beds possessing the valuable pro- 

 perty of forming hydraulic mortars and cements, for manufacturing which it is col- 

 lected from the shore and the sea-cliffs at Charmouth, and largely quarried at Lyme 

 Regis and the neighbourhood. See HYDBAULIC CEMENTS. 



The clayey members of the lias furnish a poor and cold agricultural soil, which is 

 chiefly devoted to pasture, but the land upon the marlstone is, on the contrary, of a 

 very rich and fertile description, and constitutes a district, where it prevails, that is 

 marked by the luxuriance of its crops and the excellence of the cider it produces. 

 In the upper part, it contains beds of ferruginous, brown, calcareous sandstone, which 

 is used for building purposes in the neighbourhoods where it occurs. The sandstone 

 is always more or less of a ferruginous character, but in some instances the ferruginous 

 ingredient prevails to such a degree, as to constitute a valuable ore of iron, as in the 

 neighbourhood of Blenheim, to which attention has been directed by Mr. Edward Hull, 

 of the Geological Survey. 



Like the marlstone, the calcareous sands of the uppermost portion of the liassic 

 series also furnish a rich agricultural soil. Until recently, these sands were consi- 

 dered to form the base of the inferior oolite series, but the researches of Dr. Wright 

 render it highly probable that they should, with more propriety, be classed with the 

 underlying lias, rather than with the oolitic strata. 1 



The stone found at Gotham and other places in the neighbourhood of Bristol, and 

 which has in consequence received the name of Gotham marble, and has also been 

 called ruin, or landscape marble, from the curious delineations displayed upon polished 

 sections of it, resembling trees, landscapes, &c., is a limestone from the lower part of 

 the lias. H. W. B. 



ijlBAVlVS, FUMING LIQUOK OF, is the bichloride of tin, prepared by dissolving 

 that metal with the aid of heat in aqua regia, or by passing chlorine gas through a 

 solution of muriate of tin till no more gas be absorbed, evaporating the solution, and 

 setting it aside to crystallise. The anhydrous bichloride is best prepared by mixing 

 four parts of corrosive sublimate with one part of tin, previously amalgamated with 

 just so much mercury as to render it pulverisable ; and by distilling this mixture 

 with a gentle heat, a colourless fluid, the dry bichloride of tin, or the proper 

 fuming liquor of Libavius, comes over. When it is mixed with one-third of its weight 

 of water it becomes solid. The first bichloride of tin is used in calico-printing. See 

 CALICO-FEINTING. 



XiXBETHENTTE. A hydrous phosphate of copper, named from one of its localities 

 Libethen, near Neusohl, in Hungary. 



XiXCHETJ. A certain set of plants, composed chiefly of cellular tissue devoid of 

 spiral vessels, with the stems and leaves undistinguilhable, are termed Thallogens. 

 These are of two kinds, the first admitting of two divisions : 



1. Aquatic thallogens, or such as are nourished through their whole surface by 

 water, are ALG.E. Aerial thallogens nourished through their whole surface by air 

 are LICHENS. 



2. Thallogens nourished through their thallus (spawn or mycelium) by juices da- 

 rived from the matrix are FUNGI. 



Lichens are numerous, as Ground liverwort, Cup moss, and Tree lungwort, used in 

 Siberia as a substitute for hops in brewing ; Gyropkora, employed by the hunters irt 

 the arctic regions as an article of food, under the name of tripe de roche ; Eeindeer 

 moss, and Iceland moss, much used in this country as a remedy for coughs ; the 

 Common yellow wall lichen, and some others. 



The Tinctorial lichens are also numerous. They furnish four principal colourSj 

 brown, yellow, purple, and blue. 



Gyrophora pustuldta and Sticta pulmonaria yield brown colours. The latter, witli 

 mordants of tin and cream of tartar, produces On silk a diirable Carmelite coloui*. 

 ( Guibourt.) 



Parmelia pctrietina and Evernia vulpina produce yellows ; the yellow principle of 

 the former being called chrysophanic acid, that of the latter vulpinic acid, 



* The evidence btonght forward by Dr. Wright in favour of the Hassle origin of these saftds ia 

 purely of a palaeontological nature ; physically, the most natural arrangement is to cofluect thenl 

 rather with the inferior oolite than with the lias. H. W. B, 



