90 Mr. Colqithoun on the Life and Writings [Feb. 



pound combination, refused to every other system. Green is a 

 colour which the dyer invariably produces by the mixture of 

 bhie and yellow; but the prussian blue has 7iu affinity Jor cloth, 

 and when this obstacle is overcome, it has no affinity for the 

 yelloio colouring matter; neither has the yellow any direct affi- 

 nity for the cloth ; yet there must be a combination of these 

 colours with each other and with the cloth,ox there can be no use made 

 of prussian blue in dyeing green. To effect this, the three con- 

 stituents of the green colour were applied separately. First, the 

 cloth was treated with oxide of iron, for which it has a great 

 affinity : the next step was to add to this a yellow dyestufl', 

 with which also the oxide has a tendency to combine ; and, 

 lastly, there was superinduced above all the prussic colouring 

 matter. The result was, that the oxide of iron, once combined 

 with the cloth, retained united to itself the yellow and the acid 

 colouring matters, forming as the product a beautiful and lasting 

 green. This process is now in universal practice among dyers 

 and calico-printers ; and however great the extent of its use, the 

 pleasure of seeing it universally diffused was here also the sole 

 return that ever was made to the author for his perseverance and 

 ingenuity. Men, like Berthollet, sometimes confer benefits too 

 great to be remunerated by any other than the rich reward of 

 their country's gratitude. 



We have now arrived at one of the most important and 

 instructive periods in the history of nations, the era of the 

 French revolution. It is true, that in tracing out the life of 

 Berthollet, we have heard nothing of those distractions which 

 had agitated the government of the country for years previously, 

 we have seen nothing of its financial distress, of its frequent 

 changes of ministry, of the assumption of supreme power by 

 little more than one house only of the States General, of the 

 violence offered to the King's family, of their restraint, imprison- 

 ment, and trial ; nor need we look upon the fearful sight of that 

 sun of royalty, which had so long been the vital principle of 

 France, sinking, as it seemed, for ever, in an ocean of blood. It 

 is unnecessary to give an account of these events, for important 

 as they were, they dragged not forth Berthollet from the bosom 

 of science, where he continued to prosecute his uninterrupted 

 researches. He was not, however, destined, even as a chemist 

 and man of science, long to remain unoccupied by, or unmingled 

 with, the busy ferment of the politics of the day. 



The circumstances that followed the erection of the revolu- 

 tionary government are of a kind not soon to be forgotten. It 

 will be remembered that France was then, by common consent, 

 put under the ban of every other civilized nation. To aid her, or 

 to hold intercourse with her, was ahke forbidden under the 

 severest penalties ; while ultimate success was held to be 



