[ 4-J ] 



VII. EfXtracf from a Memoir on the. Steeping of JVuol, and 

 on the Ivfiicnce of its differont States on Dj/eintr. BiJ 

 M. J. L. RoARD, Director cf the Dyeing .E.stab/)shmenf 

 in the Imperial Manvfactories. P.ead in ike French iVc- 

 iiojud Institute *. 



iNoTwiTHSTAN-DiNG the labours of Dufay, of Hellot, of 

 Macqucr, and the important investigations of Messrs. 

 Chaj)ial and BerthoHet, dyeing still presents a great num- 

 ber of problems, which are difficult to be resolved, owing 

 to the number and variety of its agents. Besides the effects- 

 produced by the nature of the primary substances, by the 

 action of water, of air, of caloric, and by the degree of at- 

 traction of the colourina; principles for vegetable and ani- 

 mal substances, di (Terences which exist in the state of the 

 substances to be dyed occasion Verv remarkable alterations, 

 M. Roard, who is charged with the superintendance of the 

 dye-houses belonging to the imperial manufactories, has 

 constantly observed that wools of various qualities, sub- 

 jected to the same experiments, were coloured in a manner 

 more or less intense, whenever he was desirous of forming 

 a comparison between them. These differences in the de- 

 gree of affinity for the colouring particles are owing to a 

 modification of the wool, of which he intends to treat in 

 anotlier memoir. 



The effects which particularly excited his astonishment 

 were those presented bv wools perfectly alike in tlieir ex- 

 ternal qualities, which assumed in the same vat very dif- 

 ferent colours. It was of the greater impDrtance to in^ 

 quire into the cause of this difference, as dyeing, wiiosc 

 influence over many of the arts is so powerful, is the basis 

 of the manufactories of tapestrv ; and as the slightest error 

 in the production of a colour reudcrs it totally useless and 

 unserviceable. This strictness in the choice of colours is 

 in an especial manner observed in the matmfaptory of the 

 Gobelins. The zeal and the exertions of M. Guillaumot, 

 and his indefatigable perseverance in destroying deep-rooted 

 prejudices, have brought that establishment to such a de- 

 gree of splendour and perfection, that the pictures of the 

 most celebrated painters are transferred to its productions 

 in a manner equally accurate and astonishing. The execu- 

 tion of the tints destined for that manulacture is at present 

 attended witli the greater difficulties, because, instead of 



• From the Annala dc Chlmi::, No. 15?. 



operating. 



