Wood Spirit.—­Wood spirit, the pure form of which is methyl alcohol, is one of the products of the destructive distillation of wood.  The wood is distilled in large iron retorts connected to apparatus for condensing the distillation products.  The heating is conducted slowly at first, so that the maximum yield of the valuable products—­wood acid (acetic acid) and wood spirit—­which distil at a low temperature, is obtained.  When the condensed products are allowed to settle, they separate into two distinct layers, the lower one consisting of a thick, very dark tar, whilst the upper one, much larger in quantity, is the crude wood acid (containing also the wood spirit), and is reddish-yellow or reddish-brown in colour.  This crude wood acid is distilled, and the wood spirit which distils off first is collected separately from the acetic acid which afterwards comes over.  The acid is used for the preparation of alumina and iron mordants (see next lecture), or is neutralised with lime, forming grey acetate of lime, from which, subsequently, pure acetic acid or acetone is prepared.  The crude wood spirit is mixed with milk of lime, and after standing for several hours is distilled in a rectifying still.  The distillate is diluted with water, run off from any oily impurities which are separated, and re-distilled once or twice after treatment with quicklime.

Stiffening and Proofing Process.—­Before proceeding to discuss the stiffening and proofing of hat forms or “bodies,” it will be well to point out that it was in thoroughly grasping the importance of a rational and scientific method of carrying out this process that Continental hat manufacturers had been able to steal a march upon their English rivals in competition as to a special kind of hat which sold well on the Continent.  There are, or ought to be, three aims in the process of proofing and stiffening, all the three being of equal importance.  These are:  first, to waterproof the hat-forms; second, to stiffen them at the same time and by the same process; and the third, the one the importance of which I think English hat manufacturers have frequently overlooked, at least in the past, is to so proof and stiffen the hat-forms as to leave them in a suitable condition for the subsequent dyeing process.  In proofing the felt, the fibres become varnished over with a kind of glaze which is insoluble in water, and this varnish or proof is but imperfectly removed from the ends of the fibres on the upper surface of the felt.  The consequence is a too slight penetration of the dyestuff into the inner pores of the fibres; indeed, in the logwood black dyeing of such proofed felt a great deal of the colour becomes precipitated on the outside of the fibres—­a kind of process of “smudging-on” of a black pigment taking place.  The subsequent “greening” of the black hats after a short period of wear is simply due to the ease with which such badly fixed dye rubs off, washes off, or wears off, the brownish or yellowish