Cheniicai Furnace for Jirong Fijfions, 345 



fires are not fufliciently ftrong for thofe operations and fufions which I have defcribed in 

 that book, I meant to comprize in that aflertion, not only the furnaces of the medical chemifts, 

 but even thofe of the manufadlurers of glafs and porcelain. For in thofe furnaces, though the 

 fire be kept up feveral days, fevera! fubftances can never be fufed, which in my furnace I 

 could bring into the ftate of fufion by a fire maintained for 'twi hours only : fucb' as the Orien- 

 tal and Bohemian garnets.) and even hyacinths. 



My furnace is nearly of thi fame conftrudtion as that which Becher has defcribed in his 

 Tripode Hermetico, page.32. The body of the furnace, A, fig. 3, plate XV. is made of ftronj 

 fheet-iron, that it may better refill: the ad ion of the fire. Its- infide is coated with crude 

 white clay, which is worked up, by means- of bullocks' blood, with an equalportion of baked 

 clay. 



B is likewife conftrudted of fheet-iron, and internally coated in the fame manner as A, 

 upon which it is placed. Through the fmall door D the coal is- put in. Into the iron 

 tube G, ferving as a flue, another, H, of the fame material is inferted, which at leafl fhoald 

 be fix feet long. The longer this pipe is, the ftronger is the. acSion of the fire ; and it 

 fhould be faftened in the chimney by means of an. iron chain, to prevent.it from overturn-: 

 ing the furnace by its weight. 



If it be defired to increafe the force of the fire, another pipe, C,mufl' be joined to the doOj 

 of the afh-pit, E, in fuch a manner, that the other extremity of C, ending in the form of as 

 funnel, may reach beyond the window, in order that the cold air maybe conveyed to the 

 furnace from a confiderablc diflance. 



The charcoal, to be employed in this furnace,' fhould be ofthe fize of a hen's or goofe's 

 egg : larger or fmaller pieces are improper, and may be ufed for other "purpof-s. The fur- 

 nace muft be filled with the fuel nearly to its top) in order that the crucible be furrounded on 

 all fides by burning coals, and that the fireimay thus exert its whole power. Nor muft it be 

 forgotten to fupply frefh coals at leafl every eight minutes, or oftener, and to fhut the 

 door every time quickly and exadUy, In this manner, any fubflance wbofe nature is fufcep- 

 tible of fufion, may be fufed within the time of two hours. 



v.. 



Brocefs ufed to feparaii the Mucilage from Linfeed Oil; Methods of diffahing Copal for Var- 

 nijh, Ufc. By Mr. TiMOTHY Sheldrake, * 



I 



HAD read in fome book, the title of which I do not recoiled, that linfeed^oil might be 

 purified by fhaking it with water, which would imbibe the impurities, and leave the oil more 

 purified. I tried this experiment by fhaking linfeed-oil with warm water, and was fur- 

 prized to find they did not feparate, but remained united in the form of emerfion. I then 

 boikd them together, and found their tendency tofeparate diminilh. As it is the known pro^ 



• Society of Arts, 1799, page 183. 



.pertjt. 



