456 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



lately published by Mr. W. Boyd Dawkins, an English natu- 

 ralist of much eminence. 



The best material for the mould in which casts are to be 

 taken is said to be artists' modeling wax, a substance similar 

 to that used by dentists. When softened and applied to any 

 object it takes the most delicate markings with perfect ex- 

 actness. The object whose figure is to be taken is first coat- 

 ed with a thin powder of steatite, or French chalk, which pre- 

 vents the adhesion of the wax. After the wax lias become 

 softened, either by immersion in warm water, or from expo- 

 sure to the direct heat of the fire, it is to be applied to the 

 original, and carefully pressed into all the little cavities. The 

 edges of the wax are then to be carefully trimmed all around, 

 if the form of the object be such as to require the mould to 

 be in one or more additional pieces in order to complete its 

 contour. Powdered steatite is again to be used to prevent 

 the several portions of the mould from adhering to each oth- 

 er, and the original is to be taken out of the mould before 

 the latter becomes perfectly cold and rigid. After wetting 

 the moulds to prevent bubbles of air lurking in the small in- 

 terstices from appearing in the object, plaster is to be poured 

 in ; or, if the mould is in two pieces, it is generally better to 

 fill each with the plaster separately, and then put them to- 

 gether. In this way the weight of the material will be re- 

 duced, and the cast itself will form a shell of a greater or less 

 thickness. 



The plaster casts are next to be dried, wholly or partially, 

 and may be then painted of any desired color ; or the color 

 may be mixed with the plaster before it is introduced into 

 the mould. After the cast is thoroughly dried it is to bo 

 steeped in paraffine, the ordinary candles answering this pur- 

 pose very well. When the cast is cold it may be polished 

 by hand with steatite, and the result will be found to be 

 much superior to that ordinarily attained by the old-fashion- 

 ed methods. It is stated that flint implements, fossils, bones, 

 and teeth can be imitated in this way so that they can scarcely 

 be distinguished from the originals. 18^1, November 25, 221. 



METHOD OF RENDERING CRUCIBLES, ETC., INFUSIBLE. 



In the increasina: demand for infusible materials for the 

 construction of furnaces, hearths, crucibles for melting glass 



