TIL 



[437] 



TIN 



shale, and the decomposition of the 

 mass uniformly produces a red soil, 

 by which character alone the out- 

 line of the division is easily defined ; 

 being always clearly separable from 

 the upper beds of the Silurian 

 system, which decompose into a 

 grey surface. Organic remains are 

 abundant, and indicate clearly the 

 lines of deposit. The fossils consist 

 of unpublished species of the fol- 

 lowing genera : Area, Avicula, 

 Bellerophon, Cucullcea, Lingula, 

 Orthoceras, Terebratula, Turbo, 

 Turritella, Trochus. This assem- 

 blage furnishes convincing proof 

 that certain genera of molluscs, 

 which have hitherto been supposed 

 to be confined to the tertiary and 

 secondary deposits, have co- existed 

 with the genera Orthoceras, Tere- 

 bratula, and Bellerophon, which 

 peculiarly characterize the older 

 strata. 



The fact may now be regarded 

 as established, that the Tilestones 

 of England belong to a deposit 

 contemporaneous with the ichthy- 

 olite beds of Caithness and Cro- 

 marty. Hugh Miller. 



The tilestones of England com- 

 pose the least of the three divisions 

 of the Old Red Sandstone system ; 

 their representative in Scotland 

 forms by much the greatest of the 

 three, and there seems to be zoo- 

 logical as well as lithological 

 evidence that its formation must 

 have occupied no brief period. 

 The same genera occur in its upper 

 as in its lower bed, but the species 

 appear to be different. Hugh 

 Miller. 



TIL'GATE BEDS, OR STRATA OF TILGATE 

 FOREST. These form the central mem- 

 bers of the Hastings beds, one of 

 the three divisions of the "VVealden 

 formation. The Tilgate strata or 

 beds consist of sand and friable 

 sandstone, of various colours ; of a 

 compact bluish or greenish grey 

 grit, in lenticular masses, its 



surface often covered with mamil- 

 lary concretions, the lower beds 

 frequently conglomeritic, and con- 

 taining large quartz pebbles ; and 

 clay or marl, of a bluish grey 

 colour, alternating with sand, 

 sandstone, and shale. Its organic 

 remains consist of bones and shells, 

 rarely occurring, ferns and stems 

 of vegetables. The Tilgate beds 

 are met with in Sussex and Kent. 

 TIN. (zinn. Germ.) A metal of a 

 white brilliant colour, slightly 

 tinged with grey, being one of the 

 simple or elementary bodies. Its 

 specific gravity is 7'0 to 7'9. It 

 fuses at a temperature of 442 

 Fahrenheit. It is of greater hard- 

 ness than lead, but not so hard as 

 gold. It is very malleable, and 

 may be beaten out into leaves 

 one two- thousandth of an inch in 

 thickness. It is more tenacious 

 than lead, and a wire of tin one- 

 tenth of an inch diameter will 

 sustain a weight of forty-seven 

 pounds. It is very flexible, and, 

 while being bent, it causes a crack- 

 ling noise. Tin unites with many 

 metals, forming valuable alloys. 

 Its symbol Sn, from its Latin name 

 Stannum. The bronze of the 

 ancients consisted of 88 or 90 parts 

 of copper, with 10 or 12 parts of 

 tin. Bell metal consists generally 

 of one-fifth of tin to four- fifths of 

 copper. The gongs of the Chinese 

 are formed of one-fifth of tin and 

 four-fifths of copper. 



Tin is mentioned repeatedly in 

 the Pentateuch. It is generally 

 believed that the Phoenicians came 

 to Britain for tin, and, from the 

 importance of the trade, that they 

 concealed the situation whence it 

 was obtained; it is certain that 

 before the time of Herodotus tin 

 was obtained from Cornwall. The 

 period at which Cornish tin was 

 first worked and exported would 

 appear to be lost in the obscurity 

 of past ages. Mr. Hawkins con- 



