a is better to let it stand four or six montfe, removiirg {he 

 mother that forms on the top novr and then, and ffnaKj se- 

 parating by filtration both this and tbetannio that has faWen 

 to the bottom. In this dissolre 32 gr, [a troy oumrej of 

 powdered gam arable ; then add the same weight of finefjr 

 powdered snlpbate of iron, snpepoxigenized by calcining it 

 iitl it grows reddish ;-aDd continoe shaking the mixture til! 

 this is completely dissolved. The ink thus made }s fine, 

 light, and of a purple tinge, but black when dried on the pa- 

 per. It is nearly, if not precbely, the composition of Gayof^s 

 ink. 



Dr. Tarry next proceeds to his indelibfe ink, the compo- lacJeTible iak» 

 sition of which howerer be does not dis^close. He says 

 .only, that it contains neither galls, nor Jog^f ood, nor bra- 

 zil, nor gum, nor arty preparation of iron ; that it is en- 

 tirely Tegetable ; and that it resists the action of the rao&t 

 powerful acids, of alkaline solutions in their most eoncew- 

 trated state, and of all solvents. He sells it in a solid form ; 

 and for use it is to be mixed accurately in a mortar with 

 eight parts of water, and then put into a bottle left at least 

 one third empty, for the purpose of shaking it, which is to 

 be done every six or eight hours for a couple of days. It 

 soon soften quills, but metallic j>ens are well adapted to it, 

 as it contain^ no acid. There is no danger from putting the 

 pen into the mouth, as it cootains nothing deleterious. . 



Nitric acid has very little action on this ink. Oximu- Action of ad& 

 riatic acid only changes it to the colour of goose dung. 

 After it has been acted on by this acid, caustic alkaline 

 solutions give it the colour of carburet of iron. The letters 

 however still remain unchanged in form, and these effects 

 require a long maceration for their production. 



From the i^eport of the committee it appears, that the Report of the 

 ink of Dr. Tarry possesses the properties he ascribes to it ; commUtte. 

 but they add, it has one of th& faults common to all 

 the indelible inks proposed, that of pretty quickly forming 

 a considerable sediment, which deprives the supernatant 

 fluid ofits properties, so that it requires to be shaken erery 

 time it is used. 



VI. a» 



and alkalis 

 oa It. 



