106 ANNUAL OF SCIENTIFIC DISCOVERY. 



must be formed, to hold them firmly, by pouring a sufficient quantity 

 of mixed plaster to produce it. With these for a nucleus, the statue 

 is then commenced to be built up with cores and mortar. The cores 

 are made by pouring a quantity of plaster on a piece of oil cloth, and 

 as it begins to harden, scoring it deeply with a knife or chisel, so that 

 when quite hard it may be easily broken into fragments of a desirable 

 size. Courses of these cores are built up around the irons, and above 

 them, until finally the entire body is finished in this rough manner, 

 the layers being cemented together by plaster mortar. The chisels 

 are then brought into play for the purpose of roughing the figure 

 (consisting of legs, body, and head) into the general human shape. 

 A long core is then dipped in fluid plaster and the end applied to the 

 shoulder. It soon adheres and forms the nucleus of the upper arm. 

 To it another core is attached to form the fore-arm. When these are 

 filled out with plaster, the whole body is covered with a coating of the 

 same, and the files brought into use, which soon produces an even sur- 

 face, taking off all irregularities. 



The advantages of these models over the ordinary clay models 



^j i/ / 



which are generally constructed, are, first, a clay model cannot be 

 changed materially after it has once been commenced, for the iron 

 skeleton which sustains every part of it is a fixture ; but in the plaster 

 work the iron frame is only in the legs, and all the rest can at any 

 time be cut apart and varied from the original design in accordance 

 with any after-thought of the artist. The plastering neither shrinks 

 nor swells from exposure, and does not require wetting or covering 

 with cloth to keep it in order. The process is less tedious than clay 

 modelling, for by means of the open files more can be accomplished 

 in a day than with clay in several days. And again, no moulding is 

 necessary to transform the form from clay to plaster ; the plaster fig- 

 ure, as it came from the artist's hands, is itself the model. Mr. Powers 

 says modelling in plaster is not new ; he only claims his way of doing 

 it as new. He considers the chief merit of his contrivance to consist 

 of the open file, which is an instrument of his own invention, and by 

 aid of which a high perfection of finish can be easily attained. 



ENCAUSTIC TILES AND CLAY MOSAICS. 



AMONG the collections of porcelain and pottery exhibited at the 

 Great New York Exhibition, were samples of encaustic tiles, and 

 mosaics of clay, intended for flooring, and exhibited by Minton & Co., 

 Stoke-upon-Trent, England. These tiles, now extensively used for 

 the flooring of churches and other buildings, are made in the follow- 



ing manner : 



The encaustic tiles are made from the wet or slip clay, pressed into 

 blocks, and faced with a finer clay, colored to the desired tint. The 

 whole is then put in a box-press, and a plaster slab, containing the 

 pattern in relief, brought down with force upon the face of the tile : 

 upon this deeply indented surface, clay, in a semifluid state, is poured. 

 This clay is generally of a deep color, and after lying twenty-four 



