Lampblack.—­Hold a piece of metal, or even a stone, over a flaring wick in a cup of oil, and plenty of soot will collect.

Sympathetic Ink.—­Nothing is better or handier than milk.  The writing is invisible until the paper is almost toasted in the fire, when it turns a rich brown.  The juice of lemons and many other fruits may also be used.  (See “Substitutes for Paper.”)

Gall of Animals, or Ox-gall to purify.—­To make ink or paint take upon greasy paper, a very little ox-gall should be mixed with it.  It is very important to know this simple remedy, and I therefore extract the following information from Ure’s ‘Dictionary.’  I have often practised it.  “Take it from the newly-killed animal, let it settle for 12 or 15 hours in a basin, pour the liquid off the sediment into an earthenware pot, and set the pot into a pan of water kept boiling until the gall-liquid becomes somewhat thick.  Then spread it on a dish and place it before the fire till nearly dry.  In this state it may be kept, without any looking after, for years.  When wanted, a piece the size of a pea should be dissolved in water.  Ox-gall removes all grease-spots from clothes, etc.”

Wafers, Paste, and Gum.—­Wafers.—­The common wafers are punched out of a sheet made of a paste of flour and water that has suddenly been baked hard.  Gum wafers are punched out of a sheet made of thick gum and water poured on a slightly-greased surface (a looking-glass for example), another greased glass having been put on the top of the gum to make it dry even.

Paste should be made like arrowroot, by mixing the flour in a minimum of cold water, and then pouring a flush of absolutely boiling water upon it.  It is made a trifle thicker and more secure from insects by the addition of alum.  Corrosive sublimate is a more powerful protection against insects, but is by no means an absolute safeguard, and it is dangerous to use.

Gum.—­The white of eggs forms a substitute for gum.  Some sea-weeds yield gum. (See also “Glue,” “Isinglass,” and “Sealing-wax Varnish.”)

Signets.—­Many excellent and worthy bushmen have the misfortune of not knowing how to write:  should any such be placed in a post of confidence by an explorer, it might be well that he should cut for himself a signet out of soft stone—­such as the europeans of bygone generations, and the Turks of the last one, very generally employed.  A device is cut on the seal; before using it, the paper is moistened with a wet finger, and the ink is dabbed over the ring with another; the impression is then made, using the ball of the thumb for a pad.

Sealing-wax Varnish.—­Black or red sealing-wax, dissolved in spirits of wine, makes a very effective stiff and waterproof varnish, especially for boxes of paper or cardboard.  It might be useful in keeping some iron things from rust:  it is the same material that is used to cover toy magnets.  When made stiff it is an excellent cement for small articles.  Opticians employ it for many of these purposes.  I have also used it as a paint for marking initials on luggage, cutting out the letters in paper and dabbing the red stuff through.