8 THE MICROSCOPICAL NEWS. 
substance of the fibre instead of being a precipitate upon or within 
It. 
We may accept this as one type of perfect dyeing upon cotton 
fibre. 
But some fast dyes are not thus incorporated into the tissue, and 
we will take a genuine red yarn of this class, and, soaking it as 
before, note the results. Along the centre of the fibre runs a deep 
red band which, on examination with a high power, shows a 
granular appearance. ‘The body of the fibre is but slightly tinted, 
and some fine granular deposits are found here and there on the 
outside of the fibre, but they adhere so closely they cannot be 
washed off without considerable frictiori. As the dyeing is prin- 
cipally effected by the central or internal deposit, and’ no dust 
comes off in the fluid, nor does any colour dissolve away to tint 
the latter,—this is clearly a perfect dye of its kind. . 
Marks of Imperfect Dyeing.—If, on the other hand, we take up 
one of the cheaper red yarns, named in imitation of the last, and 
soak and examine it as before, we will find the following results :— 
The central line of red, instead of being continuous, is broken 
up into coarse patches, while the outside of the fibre is covered 
with small grains of colour. ‘These last fall off rapidly in the fluid, 
which is soon filled with them, and the colour also dissolves and 
tinges the fluid. This, evidently, is not well mordanted. 
Again, we take one of the even body dyed cotton yarns of the 
new processes, and, steeping it a short time in our fluid, examine 
as we have done the others. There is no deposit on the outside, 
and no granular deposit in the centre of the fibre, but the tint, 
which is at first brilliant and clear, begins to grow paler rapidly, 
and in a short while tints the glycerine mixture, at first faintly, but 
soon deeper and deeper, until the colour has in great part left the 
fibre and become diffused through the glycerine. Evidently not 
well mordanted. 
The Location of Defects.—But, supposing a defect to be found, 
in what way can the microscope aid us in remedying it? If it did 
no more than locate it, or show us just in what the defect consists, 
it would be a great gain. If we found, for example, that a tin- 
mordant, with a certain dye, should throw down a pure tint in the 
fibre, uniform and clear, and our fibre shows with this mordant 
and dye irregular and uneven granular deposits of colour not pure 
in tint, there is a mistake to be rectified. If our alum should give 
us, with a certain dye, an even fine-grained deposit, and we find a 
coarse, uneven one, we see a defect to be overcome. But it does 
more than this. It gives an opportunity, by using the warm stage 
and the compressor, to perform each operation of our dyeing, from 
first to last, under the microscope, We may watch appearances 
and temperatures, and note the point at which any special defect 
