Mechanical Science. 425 



bones), well rubbed into its surface by means of a coil of list, or 

 woollen cloth, the excess being gently wiped off by a cloth. 



11. Composition for ilfoi/W.?.— Moulds, formed from a compo- 

 sition of sulphur and iron scales, have been successfully employed 

 in America in place of those usually made of brass, endurmg the 

 necessary pressure without injury. They are formed by dissolv- 

 ing the pulverised iron scales from a smith's forge in a melted sul- 

 phur: the proper proportions may be readily found by expe- 

 riment. The compound is easily fusible, and takes very sharp 

 and accurate casts from the originals. — Tech. Rep. i. 446. 



12. Cement.— The following is a very excellent cement for the 

 use of turners and artisans in general. The receipt is due to Mr. 

 S. Varley: 1 6 parts of whiting are to be finely powdered and 

 heated to redness, to drive off all the water. When cold, it is to 

 be mixed with l6 parts of black resin, and 1 part of bees-wax ; 

 the latter having been previously melted together, and the whole 

 stirred till of an uniform consistence.— Tcc/f. Rep. i. 4l6. 



13. Hyalograph.—U. de Clinchamp, teacher of the youth in- 

 tended for the marine service at Toulon, in France, has invented 

 an instrument called a Hyalograph, which takes off, with extreme 

 correctness, the appearances of natural objects. A particular 

 sort of ink serves to impress on paper designs taken on the glass of 

 the instrument ; and as the first impression cannot be erased, many 

 proofs may be taken off, by inking it over again. The hyalograph 

 serves also for many mathematical applications. The works exe- 

 cuted with hyalographic ink have the appearance of lithographic 

 designs. 



14. Blaek Lead PencjVi.— Hard black lead drawing pencils are 

 made by Mr. Varley and Mr. Banks, by melting together fine 

 Cumberland black lead in powder and shell lac. 'I his compound 

 is repeatedly powdered and re-melted, until of uniform composi- 

 tion ; is then sawn into slips, and mounted as usual. Pencils thus 

 made arc uniform, and of great strength, and there is no waste of 

 material.— TecA. Rep. i. 286. 



