STONE, ARTIFICIAL 913 



efflorescence or crystallisation, for example. Sulphate of soda, or Glauber's salt, 

 answers the purpose perfectly, and it is applied as follows : 



Average samples of the stones in their sound state, free from shakes, should be 

 sawed into pieces 2 or 3 inches cube, and numbered wilh China-ink or a graving 

 tool. A large quantity of Glauber's salt should be dissolved in hot water, and the 

 solution should be left to cool. The clear saturated solution being heated to the boil- 

 ing point in a saucepan, the several pieces of stone are to be suspended by a thread in 

 the liquid for exactly one half-hour. They are then removed and hung up each by 

 itself over a vessel containing some of the above cold saturated solution. In the 

 course of 24 hours, if the air be not very damp or cold, a white efflorescence will 

 appear upon the stones. Each piece must be then immersed in the liquor in the sub- 

 jacent vessel, so as to cause the crystals to disappear, be once more hung up, and 

 dipped again whenever the dry efflorescence forms. The temperature of the apart- 

 ment should be kept as uniform as possible during the progress of the trials. 

 According to their tendency to exfoliate by frost, the several stones will show, even 

 in the course of the first day, alterations on the edges and angles of the cubes ; and 

 in five days after efflorescence begins, the results will be manifest, and may be estimated 

 by the weight of disintegrated fragments, compared to the known weight of the piece 

 in its original state, both taken equally dry. In opposition to this, Mr. C. H. Smith, 

 one of the commissioners for selecting the stone for the Houses of Parliament, 

 states ' Such treatment, compared with that of nature, will be found to vary 

 materially, both in detail and result. If Glauber's salt expands in changing from a 

 fluid to a crystalline state, it is so little as to be inappreciable ; whereas water in- 

 creases considerably in bulk while freezing.' Many experiments selected from the 

 Eeport on Stone for the New Houses of Parliament (March 1839), show that in M. 

 Brard's treatment the effect is in most instances opposite to that of the action of the 

 weather on stones which have been exposed to its influence many years. Some of 

 the specimens well known to decay rapidly in a building disintegrated least of all 

 by Brard's process ; others of the most durable quality disintegrated more than all 

 the rest, under similar treatment ; consequently Brard's method of testing is not to 

 be depended upon, and is liable to lead to erroneous conclusions. 



The most important building-stones of the United Kingdom are the following : 



GRANITES produced chiefly in Cornwall, Devonshire, Leicestershire, Aberdeen- 

 shire, and in Wicklow and Carlow. 



PORPHYRIES, SYENITES, ELVANS obtained from Cornwall, Devonshire, Leicester- 

 shire, and many parts of Scotland and Ireland. 



SANDSTONES the chief quarries of which are in Yorkshire, Derbyshire, Shrop- 

 shire, Surrey, &c., and in several of the Scottish counties. The Darley Dale, Crag- 

 leith, and other celebrated stones, belong to this class. 



MILLSTONE GRIT is found largely in Derbyshire, in Yorkshire, and indeed in most 

 of the coal -producing districts. 



DOLOMITES, or MAGNESIAN LIMESTONES Yorkshire, Durham, Northumberland, 

 Derbyshire, and Nottinghamshire, produce these stones abundantly. 



OOLITES. The Bath Stone and Portland Stone are well-known examples of this 

 stone ; the stone from the quarries of Ancaster and of Ketton are also fine specimens 

 of the class. 



LIMESTONES. These are very varied ; the Purbeck marble, the Derbyshire marbles, 

 the Lias beds, the Devonian Limestone, and the well-known Mountain Limestone 

 being examples. 



SLATES. These are obtained in very great abundance in North Wales, in Devon- 

 shire, and in Cornwall ; in some parts of Scotland and of Ireland. 



Such are the principal varieties, although many others exist which are exceedingly 

 useful. Most of the above will be found described under their respective heads.. 



STONE, ARTIFICIAL, for statuary and other decorations of architecture, has 

 been made for several years with singular success at Berlin, by Mr. Feilner. His 

 materials are nearly the same with those of English pottery ; and the plastic mass 

 is fashioned either in moulds or by hand, being in fact a TERRA-COTTA, which see. 

 His kilns were peculiar in form, and economical in fuel, but they were in but few 

 respects different from the pottery-kilns already described. See KILN. 



Many ingenious arrangements have been made for the construction of artificial 

 stone. We might, of course, group under this head many varieties of clay-wares and 

 cements. 



Amongst all the numerous plans which have been devised, few of them have 

 altogether succeeded ; they have either proved too expensive in the manufacture, or 

 they have not endured the test of time. 



Mr. Buckwell proposed the following : Taking fragments of stone sufficiently large 

 to go freely into his mould, he fills up the interstices with stones of various sizes, and 



VOL. Ill, 3 N 



