Ink (Marking). Lunar caustic, two drachms; gum-arabic, half a drachm ; distilled water, two drachms. To be well mixed, and kept in a small stopper-bottle, and in a dark place, as the lunar caustic loses its virtue by being exposed to the light. The linen to be marked must be previously prepared with the following mixture : sub-carbonate of soda, half an ounce ; gum-arabic, one scruple; dissolved in one ounce of rain-water. With this mixture wet as much of the Linen as is to be written on. Let it become perfectly dry; then write upon it, and dry the writing in the sunshine as rapidly as possible.