374 PHILOSOPHICAL TRANSACTIONS. [aNNO J 748. 



was communicated to Dr. M. by Dr. Linneus, professor of botany at Upsal, as 

 a genuine account of this art; which he thinks has hitherto been little 

 known. 



This author tells us, " They have many large woods of beech in Smoland, 

 and other parts of Sweden, in want of which they take alder; of these they 

 are allowed to use only the old and decaying trees for this purpose, which they 

 cut to pieces, and pile in a heap, to burn them to ashes, on the ground, by a 

 slow fire. They carefully separate these ashes from the dirt or coals in them, 

 which they call raking them ; after which they collect them in baskets of bark, 

 to carry them to a hut built in the woods for this purpose. This they continue 

 to do till they have a sufficient quantity of the ashes. Then their whole art 

 follows: for which they choose a convenient place, and make a paste of these 

 ashes with water, by a little at a time, in the same manner, and with the same 

 instruments, as mortar is commonly made of clay or lime. When this is done, 

 they lay a row of green pine or fir-logs on the ground, which they plaster over 

 with this paste of ashes; over this they lay another layer of the same straight 

 logs of wood, transversely or across the others, which they plaster over with the 

 ashes in the same manner; thus they continue to erect a pile of these logs of 

 wood, by layer over layer, and plastering each with their paste of ashes, till they 

 are all expended ; when their pile is often as high as a house. This pile they set 

 on fire with dry wood, and burn it as vehemently as they can ; increasing the fire 

 from time to time, till the ashes begin to be red-hot and run in the fire. Then 

 they overset their pile with poles, as quickly as they can ; and while the ashes are 

 still hot and melting, they beat and clap them, with large round flexible sticks 

 made on purpose, so as to incrust the logs of wood with the ashes; by which the 

 ashes concrete into a solid mass, as hard as stone, when the operation has been 

 rightly performed. This operation they call walla, i. e. dressing. At last they 

 scrape off the salt thus prepared, with iron instruments, and sell it for potash; 

 which is of a bluish dark colour, not unlike the scoriae of iron, with a pure 

 greenish white salt appearing here and there in it." 



All the potash we have from Russia, Sweden, and Dantzic, is exactly like 

 what our author here describes, and seems to be made in this manner. It is 

 however generally observed, that the Russian is the best of these, on account of 

 the greater quantity of salt in it. Now if, in the preceding process, we make 

 our paste of the ashes with lie, instead of water, it is plain the potash will be 

 impregnated with more salt, and make all the difference found so between these 

 sorts of potash. This then is likely to be the practice in Russia; where their 

 wood may also be better for this purpose, and afford more salt. This is well 

 known to be the case of different kinds of wood; thus, our author abovemen- 

 tioned tells us, he obtained 2^ lb. of salt out of 8 cubic ells of poplar, which 



