402 PHILOSOPHICAL TRANSACTIONS. ^ANNO I678. 



experience proves, that watering the stones, although with water prepared by 

 lying in the sun, and poured through very small holes of a watering-pot, only 

 retards the work. In time these stones turn into a kind of vitriolic earth, which 

 swells and ferments like leavened dough. — When the bed is come to perfection, 

 then once in 4 years they refresh it, by laying new stones on the top. — ^When 

 they make a new bed, they take a good quantity of the old fermented earth, 

 and mingle with new stones, whereby the work is hastened. Thus the old 

 earth never becomes useless. 



The cistern before mentioned is made of strong oaken boards, well joined 

 and chalked. That at Deptford will contain 100 tuns of liquor. Great care 

 is to be taken, that the liquor does not drain through the beds or out of the 

 cistern. The best way to prevent this, is to divide the cistern in the middle by 

 oaken boards, chalked as before, whereby any one of them may be mended in 

 case of a defect. The more rain falls, then the more, but the weaker, will be 

 the liquor. The goodness of it is tried by weights prepared for that purpose : 

 J 4 penny weight is rich: or an egg being put into the liquor, the higher it 

 swims above the liquor, the stronger it is : sometimes the egg will swim near 

 half above the liquor. Within one minute after an egg is put in, the ambient 

 liquor will boil and froth ; and in 3 minutes the shell will be quite worn off. 

 A drop of this liquor falling on the manufactures of hemp, flax, or cotton- 

 wool, will presently burn a hole through it ; as also in woollen and leather. 



The liquor is pumped out of the aforesaid cistern into a boiler of lead, about 

 8 feet square, containing about 12 tuns, which is thus ordered : first they lay 

 long pieces of cast iron, 12 inches square, as long as the breadth of the boiler, 

 about 12 inches from each other, and 24 inches above the surface of the fire. 

 Then crosswise they lay ordinary flat iron bars, as close as they can lie, the 

 sides being made up with brick-work. In the middle of the bottom of this 

 boiler is laid a trough of lead, wherein they put at first 100 pounds weight of 

 old iron. 



The fuel for boiling is Newcastle coal. By degrees in the boiling, they put 

 in more iron, amounting in all to 1500 pounds weight in a boiling; and as the 

 liquor wastes in boiling, they pump in fresh liquor into the boiler. Hence, and 

 by a defect in ordering the fire, they were formerly above 20 days before it was 

 finished. When done, they try by taking up a small quantity of liquor into a 

 shallow earthen pan, and observing how soon it vvill gather and crust about the 

 sides of it. But of late, by the ingenious contrivance of Sir Nicolas Crisp, the 

 work is much facilitated. For at his work at Deptford, they boil off 3 boilers 

 of ordinary liquor in one week. Which is done, first by ordering the furnace 

 so as that the heat is conveyed to all parts of the bottom and sides of the fur- 



