THE AMERICAN NATURALIST [Vol. LII 



them in his descriptions of the processes of tanning. 

 Other more recent writers on tanning materials have also 

 listed oak galls, 



Dyeing.— In the history of the art of dyeing, the Aleppo 

 gall figures largely from the earliest mention of the art 

 in literature up to the very present. According to Theo- 

 phrastus it was used by the Greeks in dyeing wool and 

 woolen goods and Pliny mentioned it as being used to 

 stain the hair black and as the best adapted for the prep- 

 aration of leather and the dyeing of skins. As the an- 

 cients could not conceive of a scholar's taking an active 

 interest in the technical arts there is no record of how 

 these galls were used, merely the statements that they 

 were so used ; and it was not until the end of the eighteenth 

 century that any definite knowledge of these galls was 

 sought. 



It was at that time, when science invaded nearly every 

 field of endeavor, that the chemists made an earnest effort 

 to determine the chemical contents and action of gall- 

 nuts, so as to place the arts of dyeing and tanning on a 

 firmer and more scientific basis. Deyeux in 1793 was the 

 first to separate the tannin in the gall-nuts and his ex- 

 periments were followed up by Scheele, to whom is ac- 

 credited the discovery of gallic acid. Berthollet and 

 Fourcroy made more detailed analyses of the gall-nuts 

 and gave more positive knowledge of the various proper- 

 ties and their chemical value. 



Berthollet in "The Elements of the Art of Dyeing" 

 gave perhaps the first scientific account of the art of dye- 

 ing with full explanations of methods and materials. Ac- 

 cording to his idea the great value of the Aleppo gall lay 

 in its astringency and as it is most astringent before the 

 insect escapes, the immature galls, or as they are called, 

 the blue galls, are of the most value and are the ones used 

 in dyeing black, while the white galls, or those from which 

 the insect has escaped, are used in dyeing light linens. 

 For the dyeing of black Berthollet considered that no 



