STARCH. 443 



the skin, together with the greater part of the resinous 

 matter. The remaining portion is next mixed with 

 water, in the proportion of one pound to two gallons 

 of water, and put into copper vessels, in which the 

 mixture is boiled for four or five hours ; half an ounce 

 of soda, or a proportionate quantity of pearlash, is 

 then added to every pound of the vegetable matter 

 which is under process : the ebullition is continued 

 till the liquid acquires a tenacious consistence like 

 that of a strong solution of gum. It is then strained 

 through hair sieves, and the residuum is^expressed in 

 hair-cloth bags, by means of presses similar to those 

 used by tallow-melters, that none of the mucilaginous 

 matter may be wasted. The extract thus obtained is 

 suffered to remain undisturbed for ten or twelve hours ; 

 after which it is filtered and evaporated in lead or tin 

 vessels, placed over stoves moderately heated, either 

 by steam or fuel, until it becomes of a proper con- 

 sistence for block-printing. 



If this gum is made with the intention of employing 

 it in the manufacture of ink or paper, or in the stif- 

 fening of silks, crapes, or gauzes, no alkaline salt 

 should then be employed in extracting the mucila- 

 ginous parts ; but the evaporation should be pro- 

 longed with a moderate degree of heat, the gummy 

 extract will thus be nearly colourless, and may be 

 used in the most delicate works. 



The late Lord Dundonald, in a circular letter ad- 

 dressed to the calico-printers of Scotland, greatly 

 enlarged on the advantages accruing from this dis- 

 covery, considering it to be a national benefit. It is 

 said, indeed, to answer extremely well, and to be very 

 economical in its use ; while the collection and pre- 

 paration of the lichen afford an easy and profitable 

 employment for women and children. 



