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, IV. Objervations on prefervlng Specimens of Platits. 

 By John Stackhoufe, Efq. F. L. S. 



Read OSlober 2, 1798." 



IN profecuting my refearches with a view to complete the hiflory 

 of the Britifli Fuci, I was defirous to difcover, if poflTible, a me- 

 thod of preventing the oUve-coloiued, coriaceous fpecies from turn- 

 ing black in drying. For this purpofe I tried the experiment of im- 

 merfing them in a flrong folution of akim. The refult of my ex- 

 periment did not anfwer my expeftation. They were prevented 

 indeed from turning black, but they acquired a greenifli hue. How- 

 ever, imagining this might arife from the mixture of aluminous 

 with muriatic falts, and being of opinion that the properties of alum 

 might be of great ufe in preferviug land plants on feveral accounts, 

 I fet on foot a courfe of experiments, and am happy to fay that the 

 refult has been favourable to my expedlations. After repeated trials,, 

 during which partial failures occurred, owing to the proportioning 

 the degrees of ftrength of the folution, and the admiffion of light 

 and air during the time of drying, I can fafely recommend to the' 

 public attention the procefs which follows, not doubting but that 

 many improvements will fuggefl themfelves to thofe who pofTefs a 

 chemical knowledge of the various fubftances made ufe of by dyers 

 in fixing their colours. 



Take a faturated folution of powdered alum in common water : 

 immcrfe carefully your fpecimen, flowers, leaves and ftalk, in this 



liquor. 



