In repairing the modern road just outside the south entrance to the tunnel, a stratum of carbonized corn, beans, &c., and a quantity of burnt wood, stones, tiles, pottery, &c., was found under and above the modern road, for a distance of some Soo yds.
It has been found useful in some cases to examine microscopically the thin film of coal that often covers the pinnae of fossil fronds, in order to determine the form of the epidermal cells which may be preserved in the carbonized cuticle; rectilinear epidermal cell-walls are usually considered characteristic of Cycads, while cells with undulating walls are more likely to belong to Ferns.
In the stairs; while the objects found in them - household pottery, &c. - and near them (in some cases silos containing carbonized grain and dolia) point to the same conclusion.
It reacts most energetically with many organic compounds, removing the elements of water in many cases and leaving a carbonized mass.
The disadvantage in this process is that the by-products, such as pyroligneous acid, acetone, wood spirit, &c., are lost; as an alternative method, wood is frequently carbonized in ovens or retorts and the volatile products are condensed and utilized.
A later method consists in boiling the weed with sodium carbonate; the liquid is filtered and hydrochloric acid added to the filtrate, when alginic acid is precipitated; this is also filtered off, the filtrate neutralized by caustic soda, and the whole evaporated to dryness and carbonized, the residue obtained being known as kelp substitute.
This purified oxide, mixed with sodium chloride and coal tar, was carbonized at a red heat, and ignited in a current of dry chlorine as long as vapours of the double chloride were given off, these being condensed in suitable chambers.
Heated till the starch is carbonized, and filtered after the oil has cooled.
They are usually preserved as branching or unbranching carbonized bodies, tree-like, leaf-like or rod-like in shape, their edges regularly toothed or denticulated.
The retorts in which the coal is carbonized are almostluniversally made of fire-clay, and in all but small country works the old singleended retort, which was about 9 ft.
This method of firing results in the saving of about one-third the weight of coke used in the old form of furnace per ton of coal carbonized, and enables higher temperatures to be obtained, the heat being also more equally distributed.
As much as one-third on each ton of coal carbonized is saved by the use of machinery in the retort-house.
Here it need only be said that the masses of vegetable substance, more or less carbonized and chemically altered, of which coal is composed, frequently contain cells and fragments of tissue in a condition recognizable under the microscope, as for example spores (sometimes present in great quantities), elements of the wood, fibres of the bark, &c. These remnants, however, though interesting as revealing something of the sources of coal, are too fragmentary and imperfect to be of any botanical importance.
The skeleton as preserved is carbonized, and indicates an eelshaped animal from 3 to 5 cm., in length.