456 Mr. Rawlinson’s Colour Mill . 
thicker than usual, admitting the roller to give way to 
it, and thereby preventing any injury to the machinery. 
H, a notch in one side of the wooden vessel, serv- 
ing to regulate the depth of the water on the riddles 
DDD. 
The foregoing description is accompanied by two cer- 
tificates; one from Mr. Samuel Walker Parker, stating 
that many tons of white lead have been made, in the man- 
ner above described, at the manufactory at Islington be- 
longing to Walker, Ward, and Co. and that, since Mr. 
Ward’s plan was adopted, no other method has been 
used. The other certificate is from Mr. H. Browne, of 
Irongate, Derby ; who says that he thinks the foregoing 
invention a very valuable improvement in preparing white 
lead, and that the quality of the lead is not in the least 
injured by it. 
No. 88. 
Description of an improved Mill for levigating Pain- 
ters 9 Colours . By Mr. James Rawlins on.* 
(With an engraving.) 
THE hitherto very unmechanical, inconvenient, and 
highly injurious method of grinding poisonous and 
noxious colours, led me first to imagine a better might 
easily be contrived for that purpose. It must be obvious 
to every person, that the method hitherto adopted of 
grinding colours on an horizontal marble slab, with a 
small pebble muller, requires the body of the person 
who grinds to bend over that slab, and consequently his 
* Nicholson, vol. 11, p. 119. From the Memoirs of the Society of Arts for 
1804, — The Society awarded him the silver medaL 
