REMARKS ON THE NATURAL HISTORY OP COTTON. 177 
exposed to the same dyeing agents, do not present the same 
colours, and these are again very different from the colours 
received by animal substances. This probably depends on the 
action of the colouring substance on the materials of which the 
fabrics dyed are composed. In the cotton it has been observed 
that the dye is not diffused through the wall of the cell forming 
the hair, but that it passes through the cellulose envelope, and 
is deposited in the interior. It would be interesting to know 
more on this subject, as it is probable that some kinds of cotton, 
whose structure might easily be made out by the -.aid * of the 
microscope, receive into their interior with greater facility than 
do others the colouring matters which constitute their value after 
having been submitted to the calico-printer. 
One of the most remarkable applications of a know- 
ledge of the action of chemical substances on cotton is 
the process invented by Mr. Mercer for modifying its fibre. 
This process consists in the steeping the cotton-hair in a solu- 
tion of caustic soda. The effect of this is, to alter not only 
the microscopical appearance of the cotton-hair, but also to 
change the chemical character of the cellulose. The cotton, 
when placed under the microscope, after having been submitted 
to the soda, assumes a tubular appearance, losing its flat, 
ribbon-like, and twisted character. The cotton thus affected is 
also found to have its relation changed to the various dyes to 
which it is submitted. Under these circumstances, it is much 
more easily dyed, and exhibits brighter colours than when in 
its unchanged state. This process is extensively employed in 
the manufacture of cotton stockings, more especially for foreign 
markets. The stockings are first made loose, and after sub- 
mersion, they contract, and assume a much smaller and more 
elegant form. This process does not appear in any manner to 
interfere with the strength and durability of the manufactured 
article. 
Another point of some interest is the chemical composition of 
the ashes of the various kinds of cotton-hair. It is well known 
to the vegetable physiologist, that certain salts or mineral sub- 
stances enter into the composition of the tissues of plants, and, 
unless these substances are supplied to the soil, the plants will 
not flourish. It is on this principle that the farmer now applies 
phosphate of lime to his land, because his cereal crops will not grow 
so well without it. This constituent is present in the grains of 
wheat, and is conveyed to the bones of man from the flour ofwheat, 
which he eats in the form of bread. The sugarcane requires 
silex, or flint, in its stems, and the sugar-cultivator has found it 
of advantage to manure his crops with powdered glass, which 
contains the silex needed by the sugarcane. I throw out this 
suggestion because circumstances might occur to render it of im- 
