797 



MESODESMA. 



METALS. 



788 



mwHJja*t 



[NATROLITE.] 

 IYX, Rafinesquc, 



a genus of Pulmoniferous Motttuca 



4-0, and its specific gravity 3'3 to 3'6. It includes much that is called 

 Rhomb-Spar, or Brown Spar, which becomes maty on exposure to the 

 atmosphere. (Dana.) 



MESODESMA. [CONCHACEA.] 



MESODESMA, M. Deshayes's name for a genus of Molluica (Erycina, 

 Lam.) [VENERID.E.] 



MESOLE. ' 



MESOMPH 

 separated from Helix. 



MESOPHLCEUM. [BARK.] 



MESOTYPE. [NATROLITE.] 



ME'SPILUS, a genus of Plants belonging to the natural order 

 Bosacete, and to the sub-order Pomea. It has the calyx 5-cleft, the 

 segments foliaceous ; the petals nearly orbicular ; the disc large, full 

 of honey ; the styles 2-5, glabrous ; the pome turbinate, open, 5-celled ; 

 the eudocarp bony. The species are trees, natives of Europe, and in 

 a wild state are furnished with spines, which all disappear on culti- 

 vation. The flowers are large, nearly sessile, and white. 



M. Oermanica, the Common Medlar, has lanceolate undivided leaves, 

 downy beneath, and solitary flowers. This plant is a native of 

 Europe and Siberia. It is found in Great Britain in hedges and 

 thickets, in Surrey, Sussex, and Cheshire. It is cultivated on account 

 of iU fruit, which is eaten in a state of decay. Its taste and flavour 

 are peculiar, and greatly esteemed by some persons. De Candolle 

 describes three wild varieties of this species of Medlar. The following 

 are the garden or cultivated varieties : 



1. Blake's Large Medlar. 



2. The Dutch, Common, Large Dutch, Broad-Leaved Dutch, or 

 Large German Medlar. It bears the largest fruit of any of the 

 cultivated medlars 



3. Stoneless, or French Medlar, has small obovate fruit, not much 

 esteemed. 



4. Nottingham, Common, Small-Fruited, or Narrow-Leaved Dutch 

 Medlar. It has an obovate middle-sized fruit, and is the best of all 

 the medlars. 



If. Smithii, Smith's Medlar, has oblong elliptic serrated leaves, 

 pubescent on the nerves beneath, the flowers usually solitary. The 

 native country of this plant is unknown, but it seems to have the 

 characters of a true species. It has white flowers, which are one-half 

 smaller than those of the common Medlar. The stipules of the sterile 

 branches are large and foliaceous. 



The Medlar may be propagated by seeds or by layers, or by grafting 

 upon seedling stocks of their own species or any kind of Pomacece. 

 Forsyth remarks that the kinds of MepUui do better by grafting on 

 their own stocks. The soil best adapted to the growth of the Medlar 

 is a loamy rich earth, rather moist than dry, but not on a moist 

 bottom. It may be grown either as a standard or an espalier. The 

 general horticultural treatment should be similar to that of the 

 apple-tree. For a further account of the pomaceous genera of Kotacece, 

 see POME.K. 



(Don, Dichlamydeout Plants; Babington, M carnal of Britith Botany ; 

 Loudon, A rboretum et Pruticctum Brit.) 



METALS are elementary bodies constituting the great bulk of 

 mineral substances on the surface of the earth. They are seldom 

 found as minerals in their pure form, but united with various other 

 elements. Different opinions are entertained as to their number, 

 which arises from the circumstance that a few substances are regarded 

 as metallic in their nature by some chemists, while by others their 

 claim to this title is either doubted or denied. Thus by Berzelius a 

 substance which he discovered and called ' selenium ' is regarded as 

 a metal, but it is not so ranked by other chemists ; again, the base of 

 silica is by some classed as a metal, under the term ' silicum ;' whereas 

 many consider it as more nearly allied in nature to boron, and call 

 it 'silicon.' 



Independently of these, the metals, including those which have 

 been longest known, as well as some whose claims are even yet some- 

 what doubtful, amount to 48 ; they are as fallows : 



Potassium 

 Sodium 

 Lithium 

 Barium 

 Strontium 

 Calcium 

 Magnesium 

 Lanthanum 

 Didynium 

 Cerium 

 Yttrium 

 Erbium 

 Terbium 

 Gluciutn 

 Aluminum 

 Thorinum 

 Zirconium 

 The two last are doubtful. 



Titanium 



Tantalium 



Niobium 



Pelopium 



Tungsten 



Molybdenum 



Vanadium 



Chromium 



Uranium 



Manganese 



Arsenic 



Antimony 



Tellurium 



Bismuth 



Zinc 



Cadmium 



Tin 



Lead 



Iron 



Cobalt 



Nickel 



Copper 



Mercury 



Silver 



Gold 



Platinum 



Palladium 



Rhodium 



Iridium 



Rutherium 



Osmium 



Ilmenium (?) 



Norium (?) 



The following are the general properties of the metals. With the 

 ingle exception of mercury, they are all solid at the usual temperature 



of the air, and the colour of most of them is grayish-white. Silver is 

 of a pure white; tin, cadmium, platina, palladium, mercury, and 

 iridium, are white, with a slight shade of gray ; antimony is white, 

 with a slight bluish tint ; cobalt, nickel, iron, manganese, and rhodium, 

 are more gray ; lead and zinc are of a bluish-gray ; chromium, 

 molybden, and tungsten, are of a pure gray colour ; uranium is brown ; 

 gold, yellow ; copper and tellurium, yellowish-red ; &o. 



The lustre of metals is great and peculiar, and is well known by 

 the name of the ' metallic lustre ;' they differ however very consider- 

 ably in the degree in which they possess this property. Professor 

 Leslie arranges them as follows, the first possessing the greatest 

 lustre : Platina, silver, mercury, gold, copper, tin, and lead. When 

 reduced to a state of minute division, as by filing, or by any other 

 means, the metallic lustre is lost, but the colour remains. The metals 

 are generally reckoned perfectly opaque, even when reduced to thin 

 leaves; but it is found that gold-leaf, which is l-200,000th part 

 of an inch thick, suffers light to pass through it, and it has a green 

 colour ; it is therefore extremely probable that all metals, if they 

 could be rendered equally thin, would also be translucent. There 

 are some metals, such as lead, tin, copper, and iron, which, when 

 rubbed, emit a peculiar and disagreeable smell. There are others 

 which yield a peculiar odour when heated and vaporised; this is 

 especially the case with arsenic, and it occurs also with antimony ; 

 the greater number of the metals are however inodorous ; a few of 

 them possess taste, but it is in all cases disagreeable. 



Formerly great density and a specific gravity superior to that of 

 other bodies were considered as among the principal characteristics of 

 metals. But the brilliant discoveries of Sir H. Davy have proved that 

 substances which are even lighter than water potassium and sodium 

 for example possess every property which belongs to metals. The 

 density of all the metals has not been ascertained. Beginning with 

 the lightest, their specific gravities are as follows : 

 Potassium . . . 0-865 Cadmium . . 



Sodium 

 Titanium 

 Columbium 

 Arsenic . 

 Chromium . 

 Tellurium 

 Antimony . 



Zinc 

 Iron 

 Cobalt 

 Nickel 



0-972 

 5-300 

 5-610 

 5-884 

 5-900 

 6-115 

 6-702 

 7-050 

 7-191 

 7-770 

 7-834 

 8-279 



Copper . 



Uranium 



Bismuth . 



Silver . 



Rhodium 



Lead . 



Palladium 



Mercury 



Tungsten 



Iridium 



Gold 



Platinum 



8-694 

 8-958 

 9-000 

 9-830 

 10-474 

 10-649 

 11-445 

 11-860 

 13-568 

 17-600 

 18-680 

 19-361 

 21-530 



ductile or malleable, arranged alpha- 



The following metals are 

 betically : 



Cadmium 



Copper 



Gold 



Iridium (?) 



Iron 



Lead 



The following metals are so brittle that the greater number of them 

 may be reduced to powder : 



Antimony 



Arsenic 



Bismuth 



Cerium 



Chromium 



Mercury 

 Nickel 

 Osmium (!) 

 Palladium 

 Platinum 



Cobalt 

 Columbium 



Manganese 



Molybden 



Bhodium 



Potassium 



Silver 



Sodium 



Tin 



Zinc 



Tellurium 

 Titanium 

 Tungsten 

 Uranium 



The degrees of ductility and malleability of those metals which 

 possess those properties are very different ; and some metals are so 

 totally devoid of them that they may be broken by the hammer, and 

 even reduced to powder. Ductility is that property by which metals 

 are susceptible of being drawn into wire, and malleability is that by 

 which their form is changed, so that they are beaten into thin leaves 

 under the hammer or extended by pressure. The annexed tables show 

 that the metals mentioned in them do not follow in the same order as 

 to those properties. 



Order of Ductility. 

 Gold 

 Silver 

 Platina 

 Iron 

 Copper 

 Zinc 

 Tin 

 Lead 



Order of Malleability. 

 Gold 

 Silver 

 Copper 

 Tin 



Platinum 

 Lead 

 Zinc 

 Iron 



The ductility and malleability of metals are in general considerably 

 increased by heat, but only to a certain extent. There are some metals 

 which are malleable only between two very near degrees of tempera- 

 ture ; such, for example, is the case with zinc. 



The degree of tenacity of metals is indicated by the powers of their 

 wires in supporting a given weight. The following weights are capable 

 of being sustained by wires of the annexed metals about 0'840 of a 

 line in diameter : 



