Mechanical Science. 135 



posed shape, is in a state to receive the drawing of the pattern ; this 

 being put in, a blunt steel tool, or burnisher, or die, is to be ap- 

 plied successively to all those parts of the pattern intended to be 

 in relief, and at the same time is to be driven very cautiously, 

 without breaking the grain of the wood, till the depth of the de- 

 pression is equal to the subsequent prominence of the figures. The 

 ground is then to be reduced by planing or filing to the level of 

 the depressed part ; after which the piece of wood being placed in 

 water either hot or cold, the parts previously depressed will rise 

 to their former height, and will thus form an embossed pattern, 

 which may be finished by the usual operation of carving. — Trans, 

 Soc. Arts. xlii. 52. 



4. Drawing of Iron Wire facilitated. — A manufacturer of iron and 

 steel wire observed that the wire which had been pickled (a pro- 

 cess requisite in the course of the drawing) in an acid liquor, the 

 temperature of which had been raised by ^;he immersion of some hot 

 ingots of brass, passed through the holes in the drawing plates with 

 remarkable facility, in consequence of the precipitation of a portion 

 of the copper in the liquor upon its surface ; it required to be an- 

 nealed much less frequently than before, the copper apparently 

 preventing the action of the plate so as to gall or fret the wire. 

 In consequence of this fact, the same person has constantly availed 

 himself since of the use of a weak solution of copper in iron and 

 steel wire- drawing. The thin coat of copper is entirely removed 

 in the last annealing process. — Tech. Rep. vii. 161. 



5. Hawkins* mode of preparing Emery. — Mr. Hawkins finding that 

 the emery sold in the shops was totally inefficient for the purpose 

 he had in view, namely,grindingtwoflat surfaces of hard cast steel 

 accurately, thought of applying a process he had seen for washing 

 over diamond dust., to emery ; and to be certain that his emery was 

 of good quality, he purchased of an emery-maker a quantity of those 

 small lumps, or grains, which had longest withstood the action of 

 the cast-iron runners and bed, and thus ensured the hardness of 

 the emery ; these pieces were reduced to powder in a cast-iron mor- 

 tar, and then separated into different portions by sieves. 



He then washed over the finest emery thus obtained, using oil 

 instead of water, as in the usual process, the former holding it in 

 suspension for a much longer time ; and in this way obtained a 

 series of emery which had floated one, five, ten, fifteen, twenty, 

 forty, and eighty minutes, amongst which Jte found every variety 

 necessary for his purpose ; and keeping them in boxes, which were 

 numbered according to the minutes they had floated, he could at 

 any time prepare more of any one kind. In this way Mr. Haw- 

 kins readily attained his object, and ultimately by selecting those 

 grains of emery which resisted longest the action of the pestle and 



