270 Mr. Delaval on the Cauj'e of the 



undiluted, as a hlack fubftance. * The fame an* 

 thor informs us, that the fpecies of Tyrian dye, 

 •which was' moft efteemcd, was of a rofe colour 

 inclining to hlack; f and that the red was inferior 

 to that which was blacker. % He accurately dif- 

 tinguifhes the bright red colour, which is tranf- 

 mitted through the dyed clothes, from the dark 

 hue, which they exhibit when viewed by incident 

 light. II 



The inattention of later philofophers, and arti/ls, 

 to the refleflive, and tranfmiffive, qualities of the 

 conftituent parts of Coloured Subftances, has, 

 doubilefs, impeded theprogrefs and improvement 



* Plinil, L. XXXV. C. 6. Ah hoc maxima autoritas 

 Tndico. Ex India venit harundinum fpumx adhaerefcente 

 limo. Cum teritur nigrum. At in diluendo mixturam 

 purpura: csruleique mirabilem reddit. 



f lb. L. IX. C. 36. Purpura; florem ilium tingendis 

 veftibus expetitum, in mediis habent faucibu'. Liquoris 

 hie eft minimi in Candida vena, unde pretiofus ille bibitur 

 nigranth rofa; colore fublucens. 



X lb. L. IX. C. 38. Rubens color nigrante deterior. 



(I lb. L. IX. C. 38. Laus ei fumma, color fanguiiiis 

 concreti, nigricans affeRu, \Azm(\\.\t fujfedu refulgens. 



It appears from the following paflage, cited from Macro- 

 blus, that the dealers in dyed clothes were accuflomed to 

 confider the colours, which they yielded by tranfmiflion, as 

 well as thofe which they afforded, when viewed by inci- 

 dent light. " Cum de Tyria; purpura, quam emi jufferat, 

 obfcuritate quereretur (Auguftus) dicente venditore, crige 

 altius et fufpice, his falibus ufus eft: Quid? ergo ut me 

 populus Romanus dicat bene cultum, in folario ambula- 

 lurus fum ?" Macrob. Lib. II. Saturn. 



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