for pointing Needles. 263 



which it enters, and carries with it the fine particles of steel 

 and sand, which it deposits on the lower part of the inside 

 of the wet cloth, which forms the connection between the 

 sides of the case, by these means rendering the operation of 

 pointing needles less pernicious to the health of the opera- 

 tor. The stone may be worked by hand, by water, or ma- 

 chinery. 



I am, sir, most respectfully, 



GieatBerkhampitead, Heits, jaauary25, 1811. ThOMAS VVoOD. 



To a Taylor, M.D. Sec. 



Description of the Engraving of Mr. Thomas Wood's 

 hnprovement in the Grindstones for Pointing Needles. 

 Plate VL fig. 1. 



The grindstone A is inclosed in a box or case, formed of 

 two circles ofwo(Kl, one marked B, and another on the 

 opposite side, which cannot be seen in this view; a a are 

 two thir* iron plates placed so near to the stone, as to be as 

 close to it as possible without touching it ; two other plates 

 b, support a pane ot glass at c, which at the same time that 

 it prevents the dust from being thrown over the stone into 

 the air, admits light to that part of the stone where the 

 needles are applied ; the remaining space between the edges 

 of the two circular boards B, is filled up by a coarse ploth 

 D, which encompasses about f of the edge of the stone, 

 and is then l)_ooked up to the iron plates a, by means of two 

 bent pieces of plate iron, to which the cloth is sewed, one 

 of which is seen at d ; and these are hooked upon other bent 

 pieces, which form part of the plate aa; the cloth is wetted 

 when put on, and will then catch the dust which is pro- 

 duced by the grinding, and when it has accumulated much, 

 by unhooking the cloth it may be sliook out, and the cloth 

 being wetted is hooked on again ; as the stone wears down 

 the piece of plate iron e, situated in a groove formed by 

 the edges of the plate a, is slided forwards to follow up the 

 reduced edge of the stone, and other plates are put into tlie 

 groove after e, when they are required ; the case B is sup- 

 ported by a cross-bar of the frame in which the stone re- 

 volves, and which n)ay be made in this or in any other 

 form; the stone is turned in the usual manner of grnuiinii- 

 mills for needles, hv a strap passintr round a rigger, fixed on 

 llie end of its spindle ; but this caimot be seen ui this view. 



it being hidden behind the stone. 



XXXIX. De- 



