758 Transactions of the American Institute. 



water of a disturbed spring well will become clear in the face of the 

 descending muddy water, and that almost before he has ceased to 

 stir it; and, moreover, that all such ascending waters (no matter 

 what compose the strata through which they ascend), become per- 

 fectly defecated from all particles, though not purified or freed 

 from the impregnated properties of the mineral strata, through 

 which they have been leaching in their upward passage, whether 

 they have been thus impregnated with salt, sulphur, or combined 

 chemicals. 



And we find this principle of leaching recognized and adopted 

 by the experienced chemist, who scientifically leaches upwards 

 through a suitable glass vessel, provided with a filling of sponge, 

 or such other filtering substance as may be required by the pecu- 

 liar properties of the material under operation, or the purposes for 

 which the operator needs the solution; this system of leaching 

 being essentially requisite in instances where the material is too 

 gummy to admit of being leached downwards, or that a liquid well 

 defecated from all foreign particles is needed; and when perfect 

 defecation is not necessary, and that the nature of the ingredient 

 will admit of a downward leaching, while a concentration of the 

 virtues is alone wanted, then the operator having placed his ingre- 

 dients in a suitable position for percolation, performs his operation 

 with a wMm'mww amount of ^i«tZ, supplying it through a percolating 

 diaphragm of paper in a gentle sprinkling or trickling on to the 

 surface of the ingredient, from whence it passes through each par- 

 ticle of the mass, and is constantly returned to the surface, till as 

 much of the valuable properties of the ingredient as are readily dis- 

 solved in water, wine or alcohol, are impregnated with or carried 

 down by the liquids to the provided receiver beneath the mass 

 operated on. 



I will now advert to a few more familiar facts, and examine them 

 in their narrower and more direct bearing on dissolving and remov- 

 ing the astringent salts or tannic acid from bark by " steaming it in 

 a damp condition," the retention of the tannic acid by every sepa- 

 rate particle of the tan, and its removal: 



1. Water will be found to enter but a short distance into a barrel 

 of flour, immersed in it for weeks. 



2. Starch, meal and flour boiled in water, after it has been care- 

 lessly thrown in, will form into lumps, dry in the inside, the water 

 having never penetrated to the center of the lumps. 



3. A nutshell, which requires great force to break it by an 



