roh. XLV.] PHILOSOPHICAL TRANSACTIONS. 5/5 



was very sharp and caustic; but the same quantity of birch afforded only 1 lb. of 

 salt, and that not so strong; and fir hardly yielded any at all. 



The way of making potash above described may be the more easily understood 

 by our people in America, for whom this is chiefly intended, as it is the same 

 with their way of making lime of shells, the only lime they use in most places. 

 These shells they burn to lime between the layers of a pile of wood, instead of 

 a kiln, till it is reduced to ashes, in the same manner as is here directed to be 

 done with ashes, to make potash. The lime thus made is reckoned very good; 

 but as it is impregnated with the ashes of the wood, and the marine salt that is 

 often in the shells, it is apt to make the houses that are built with it very damp 

 in moist weatlier, so that the water often runs down their walls in streams; which 

 cannot but be very unwholesome in an air that is naturally close and damp; the 

 only way to prevent which would be, to wash and dry their shells frequently, and 

 burn them in dry pine, that afford little or no lixivial salt. 



3. There is another way of making potash, practised chiefly in England, 

 where they make it in the following manner. 



With their ashes of fern, or wood of any kind, they make a lie, which they 

 reduce to what they call potash, by burning it with straw. To do this, they 

 place a tub full of this lie near a clean hearth of a chimney, in which they dip a 

 handful of loose straw, so as to take Up a quantity of Ke with it. The straw 

 thus impregnate;! with lie they carry as quickly as they ca% to hold it over a 

 blazing fire on their hearth, which consumes their straw to ashes, and at the 

 same time evaporates the water from the salts of the lie.. Over the blaze of the 

 the first parcel of straw they bum another dipped in lie in the same manner. 

 This they continue to do till their lie is all expended. By this means the coals 

 and ashes of the straw, and salts of the lie, are left on the hearth, and concrete 

 together into a hard solid cake of a greyish black colour, which they scrape off, 

 and sell for potash. 



This is an easy way of making potash, when in want of proper vessels to ex- 

 tract the salt of the lie by evaporation, or in want of wood to reduce the ashes 

 to potash in the way abovementioned, for which it seems to be contrived, and 

 for which it is only to be commended. For the potash made in this manner is 

 full of the coal of the straw, and its salt is not so strong, nor so sharp and cor- 

 rosive as the salt of the foreign potash, calcined in an open fire; besides other 

 differences hereafter mentioned, which makes this potash unfit for some pur- 

 poses, and not above half the value of the foreign. 



4. They have a very different way in the north of England of reducing their 

 kelp to potash, which they use for making alum. This is made of the different 

 kinds of fuci, or sea-weeds thrown up on the shore, or gathered on the rocks; 



(which they dry a little in the sun, and afterwards burn them in a kiln, built of 



