manifest.  This is simply because the colour or dye only penetrates a very little way down into the substance of the felt, until, in fact, it meets the proofing, which, being as it ought to be, a waterproofing, cannot be dyed.  It cannot be dyed either by English or German methods; neither logwood black nor coal-tar blacks can make any really good impression on it.  Cases have often been described to me illustrating the difficulty in preventing hats which have been dyed black with logwood, and which are at first a handsome deep black, becoming rather too soon of a rusty or brownish shade.  Now my belief is that two causes may be found for this deterioration.  One is the unscientific method adopted in many works of using the same bath practically for about a month together without complete renewal.  During this time a large quantity of a muddy precipitate accumulates, rich in hydrated oxide of iron or basic iron salts of an insoluble kind.  This mud amounts to no less than 25 per cent. of the weight of the copperas used.  From time to time carbonate of ammonia is added to the bath, as it is said to throw up “dirt.”  The stuff or “dirt,” chiefly an ochre-like mass stained black with the dye, and rich in iron and carbonate of iron, is skimmed off, and fresh verdigris and copperas added with another lot of hat-forms.  No doubt on adding fresh copperas further precipitation of iron will take place, and so this ochre-like precipitate will accumulate, and will eventually come upon the hats like a kind of thin black mud.  Now the effect of this will be that the dyestuff, partly in the fibre as a proper dye, and not a little on the fibre as if “smudged” on or painted on, will, on exposure to the weather, moisture, air, and so on, gradually oxidise, the great preponderance of iron on the fibre changing to a kind of iron-rust, corroding the fibres in the process, and thus at once accounting for the change to the ugly brownish shade, and to the rubbing off and rapid wearing away of the already too thin superficial coating of dyed felt fibre.  In the final spells of dyeing in the dye-beck already referred to, tolerably thick with black precipitate or mud, the application of black to the hat-forms begins, I fear, to assume at length a too close analogy to another blacking process closely associated with a pair of brushes and the time-honoured name of Day & Martin.  With that logwood black fibre, anyone could argue as to a considerable proportion of the dye rubbing, wearing, or washing off.  Thus, then, we have the second cause of the deterioration of the black, for the colour could not go into the fibre, and so it was chiefly laid or plastered on.  You can also see that a logwood black hat dyer may well make the boast, and with considerable appearance of truth, that for the purposes of the English hat manufacturers, logwood black dyeing is the most appropriate, i.e. for the dyeing of highly proofed and stiff goods, but as to the permanent character of the black colour on those stiff hats, there you have quite another question.  I firmly believe that in order to get the best results either with logwood black or “aniline blacks,” it is absolutely necessary to have in possession a more scientific and manageable process of proofing.  Such a process is that invented by F.W.  Cheetham (see Lecture VII. p. 66).