Ashes
Aiton's Encyclopedia (1910)
the earthy, mineral substances left after burning. They are the part of an animal or plant that cannot be burnt. Ashes consist largely of lime, sand, soda, and potash, and may contain sulphur, phosphorus, zinc, copper, iron, and other elements. Different parts of a plant or animal yield ashes of different composition. It is quite possible for a chemist to determine the source of many ashes. He would have no difficulty, for instance, in distinguishing between the ashes of a cigar and those of a corncob; or between the ash of maple sugar and that of raw cane sugar. How plants, growing side by side in the same soil, can store up different solid materials in their tissue is an interesting problem. Certain seaweeds, growing wholly afloat in salt water, notably on the coast of Ireland, yield ashes rich in iodine, yet no trace of iodine can be found in the sea water. It would seem that each species has the ability to select the earthy food of its own desire. A plant accepts a substitute so far as it can, taking more magnesia, for instance, in case lime is scarce; but in general the farmer and gardener may accept the double lesson taught by ashes,--first, that the soil must supply what the plant needs or it will not grow, and secondly, that soil will best raise the kind of plants for which it has the requisite sort of food. Lye obtained by leaching or allowing water to trickle through an ash barrel or a hopper of ashes has long been used for soap making. Hardwood ashes, especially those of hickory and maple, are the best for this purpose. Wood ashes are also an excellent fertilizer for fields. They should be well scattered, however. The ashes of coniferous trees, as pine and fir, have little value for either purpose. It is incorrect to speak of a volcano as sending forth smoke and ashes. Volcanic "ashes" are only finely powdered pumice. In oriental countries it has been the custom from Bible times to sift ashes on the head, in token of extreme misery. Something of the sort among the early Christians gave the name of Ash Wednesday to the first day of Lent. See Alkali
What Has Changed in the Last Century
Aiton's chemistry of 1910 still holds: ash is the incombustible mineral residue, largely lime, potash, soda and silica, and hardwood ash remains a good source of potassium for gardens, though farm fertiliser now comes from mined potash rather than the ash hopper. Two claims have not aged well. Seawater does contain iodine ut at only about 60 micrograms per litre, far below what 1910 analysis could catch, so the Irish kelps were concentrating it rather than conjuring it; and the plant's "ability to select the earthy food of its own desire" is now traced to specific ion-transport proteins in root cell membranes. The warning that volcanoes send out no true ashes lost its battle with usage: "volcanic ash" is standard technical language for the fragmented glass and rock that closed most of European airspace after Iceland's Eyjafjallajokull erupted in April 2010.
Written for this edition, 2026.