On the Preparation of Crayons for Drazvhig, &c. 299 



tions alfo a difeafe which affefts the neck and head of cats, 

 bv which the greater part of thefe animals in Weftphaha 

 died; and refers to a palTage in Sauvage's No/ologia*, which 

 however, in an extra6l of that work in three large volumes 

 o£lavo t, now before me, I have not been able to find. 



XIV. On the Preparation of Crayons nfed for Drawings 

 from the Pajle of Reddle. By C. F. LoMET J. 



I 



N mofi: drawing-fchools, and particularly thofo at a dif- 

 tance from the capital, many difficulties are experienced for 

 want of good crayons. Thofe fawed from red chalk, which 

 are in common ufe, are almoft always hard, gritty, and 

 often of an unequal confiftency ; fo that the touches in the 

 drawings for which they are ufed can never have the ftrcnslh 

 or corrc6lnefs neceflary to produce the defired effoft. The 

 only good crayons ufed in France are manufoftured exclu- 

 (ively at Paris, where they are fold very dear : the heft fort 

 have been long known by the name of the pafte- crayons of 

 DcfmaretSy who apparently was the inventor. As no author 

 who has written on the compofition of thefe crayons has 

 pointed out the proportions of the ingredients neceffar)'' to 

 be ufed, I made many trials with every combination of the 

 fubftances that appeared to me proper for making thera. 

 I rdjefted thofe products which did not anfwer the objects 

 of my refearch ; and I here fubjoin thofe mixtures that 

 gave me fatisfaftory refults. 



Thefe pencils are compofed of the foftcr kind of reddle, 

 which is an oxyde of iron mixed with earth of an argilla- 

 ceous nature, and called hematites^ or bog-ore. It muft be 

 incorporated with fome agglutinating fubftance, fuch as 

 gum, fize, or rtfm ; to which fometimes foap is added, tu 



* NoCul. cl. X. art. 30. 8, 



t Amft. 1763. 



} From the Annates de Chimie, No. 90. an. 7. 



foften 



