PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 889 



of jiotash) than when given through the exceedingly unscientific, 

 clunis}', and oftinies repulsive expedient of serving out lemon juice 

 to the men. It might also be worth while to ascertain whether the 

 desired end could not be secured by letting chloride of potassium 

 partially replace chloride of sodium (common salt) in the pre- 

 servative process to which the provisions are subjected. 



Mr. J. H. Gray exhibited a model, and gave the following des- 

 cription of his ingenious 



Mill Stone Dressing Machine. 



The purpose of this invention is to assist millers in performing 

 the difficult and la1)orious task of dressing or picking flour mill 

 stones. The operation of dressing mill stones consists in cutting 

 fine parallel lines in the operative surface of the stones, some 

 millers claiming to make as many as from thirty to forty lines in 

 the space of an inch ; even the fine lines made with a diamond 

 have been used for this purpose. 



This operation has to be repeated al)out once a week, and to 

 perform it in the ordinary way is a very difiicult and laborious 

 task. In fact, it may be considered a fine art, for none except 

 those "who have become skilled by long and patient practice can 

 execute it properl3\ 



Few millers possess the ability to perform this work satisfiicto- 

 rily, and as the quantity and quality of the flour produced depends 

 much on the accurate manner in which the stones are dressed, con- 

 sequently it is evident that by the old process an immense loss is 

 occasioned by the lack of skill on the part of millers. 



By the aid of this machine the work can be executed by an 

 mi&killful miller in an easier, quicker and more accurate manner 

 than it is possible for the most skillful with the handpick. 



The following difference was found in favor of using the machine 

 over the old process, by a test made at Messrs. Wright & Ton's 

 mill, North Leominster, Mass. A quantitj^ of wheat was weighed 

 and ground with the stones dressed by the old process, and the 

 results noticed. Then the stones were dressed with the machine, 

 after which the same quantity and quality of wheat was ground, 

 the result of which was an increase in the quantity of flour pro- 

 duced, of four and three-tenths per cent, in favor of using this 

 machine. 



Samples of the flour were inspected by superior judges, who 

 pronounced that which was produced after using the machine as 

 worth one dollar most per barrel. 



