50 
MR. HORNER AND SIR DAVID BREWSTER ON 
of 38 lbs. of dry lime to 1000 lbs. of cloth. The cloth is boiled in this liquor from four 
to six hours, the lime acting' as an alkali ; and it is used only from being considerably 
cheaper than potash or soda. After this boiling, the cloth is taken to the dash-wheel 
to be thoroughly cleared of the lime, which is effected by its being tossed about for 
ten minutes in clear water in the interior of one of the compartments into which the 
wheel is divided. Here, then, is the source of the calcareous matter of the incrusta- 
tion ; and we have the lime dissolved or suspended in the water in a state of extremely 
minute division, and from which it is deposited, most probably, by a partial evapora- 
tion. It is difficult to say whether the deposit takes place while the wheel is revolving, 
by the water being broken into a kind of spray, and so presenting a greater surface 
for evaporation, or during the night, when the wheel is still: some of the properties, 
to be afterwards described, render the latter supposition the most probable. But in 
whatever way it takes place, the operation is an exceedingly gradual one ; for the 
wheel had been in constant use for ten years, and the coating in the interior did not 
exceed one tenth of an inch in thickness. It had been in operation about two years 
before any perceptible deposit showed itself in the inside ; but it had not been going 
half a year before an incrustation began to be formed on the outside of the wheel. I 
remarked that the deposit was in greatest quantity around the orifice where the cloth 
is put in and taken out. The deposit in the interior, and which coated the whole 
surface of the compartment, was of a darker brown colour, and was as smooth and 
splendent as a lining of highly polished bronze would have been. The high polish is 
no doubt partly produced by friction ; and I observed that it was highest on that part 
of the outside nearest the opening. 
So far we have calcareous , but no animal , matter ; but in going a little further back 
in the history of the process to which the cotton had been subjected, before it came 
to the bleach-field, I discovered that animal matter might be contained in the incrus- 
tation. I learned that the cloth had been woven in power-looms ; and on making in- 
quiry as to the composition of the dressing or paste used to smooth and stiffen the 
warp before it is put into the loom, I was told that in the factory from whence the 
cloth had come, it is the practice to mix glue with the wheaten flour, generally in 
equal proportions by weight. 
We have thus lime and gelatine, the same materials which are employed by the 
molluscous animal in the formation of its covering, and apparently in the same de- 
gree of minute division as that in which they are exuded from its mantle. 
Chemical examination of the Substance. 
] . The external deposit . — Exposed to the flame of a wax candle, it blackens, and 
gives out the usual smell of burning animal matter, the thin laminae of which it is 
composed separating and curling up like films of horn ; appearances similar to those 
exhibited by membranous shells when heated. When the flame is urged by the blow- 
pipe, the laminae separate still more, and are changed into an extremely light and 
