C 424 J 



cording to the teftimony of the kamed Profeflbr Berg i us, 

 is not taken up till it is eleven or twelve years old, which 

 alone may perhaps be found fufficient to conftitute the 

 difference. This circumftance at leaft feems to deferve 

 future inquiry. In the interim, let us endeavour to afcer- 

 tain their comparative virtues. 



With refpeift to the fpecimens of Englifh rhubarb No. I. 

 and No. II. which were lately committed to my exami- 

 nation by our worthy Secretary, I have hitherto only had 

 opportunity of making the following trials. The (hrivelled 

 fcabrous appearance of thefe fpecimens feems to denote 

 fome material defeft to have taken place in the article of 

 drying and curing the roots, which can only be learnt by 

 experience. 



It may not be improper to hint, that all the larger roots 

 ought to be perforated through the centre, this part of the 

 plant being the moft liable to decay, and the procefs of dry- 

 ing ought to be performed with expedition. The proper 

 degree of heat may be afcertained by dint of obfervation, 

 and adjufted with accuracy by the thermometer. 



Experiment I. Four tlnftures were drawn by macerating 

 Turkey, Eaft-Indian, and the Englifh rhubarbs No. I. and II. 

 of each half a drachm in an ounce of proof fpirit, in four feparate 

 vials, for three days. The tinftures, being ftrained and filtered, 

 appeared nearly fimilar as to fmell and colour, only the two for- 

 mer feemed rather more aftringent and aromatic to the tafte. 



Exp. II. Tofixty drops of each of thefe tinftures, was added 

 a fingle drop of a folation of fait of fteel in a fmall glais. The 

 two tinctures of foreign rhubarb almofl inftantly aiTumed a dufky 

 green, inclining to black, while the tinflures of the Engliih rhu- 

 l)5trb only acquired a darkifli brown colour. 



Exp, IU. 



