As for the trees themselves, the one that bears the acorn of largest size is known as the “hemeris;”[2245] a small tree with a thick bushy foliage all around it, and often hollowed at the place where the branch is joined to the trunk. The quercus has a stronger wood, and less susceptible of decay: this also is a very branchy tree, but is much taller than the last, while the trunk is considerably thicker. The ægilops,[2246] however, is the highest of them all, and is much attached to wild, uncultivated spots. Next to this in height is the latifolia, but its wood is far from being so useful either for building purposes or for charcoal. When rough-hewn it is very apt to spoil, hence it is that it is generally used in an unhewn state. As charcoal, it is considered only economical in smelting copper; for the moment the workman ceases to blow, the fire dies out, and hence it requires to be repeatedly rekindled; while at the same time it gives out great quantities of sparks. The best charcoal is that obtained from the wood of young trees.[2247] Square billets of wood, newly cut, are piled compactly together with clay, and built up in the form of a chimney; the pile is then set fire to, and incisions are made in the coat of clay as it gradually hardens, by the aid of long poles, for the purpose of letting the moisture of the wood evaporate. The worst kind of all, however, both for timber and for making charcoal, is the oak known as the “haliphlœos,”[2248] the bark of which is remarkably thick, and the trunk of considerable size, but mostly hollow and spongy: it is the only one of this species that rots while the tree is still alive. In addition to this, it is very frequently struck by lightning, although it is not so remarkably lofty in height: for this reason it is not considered lawful to employ its wood for the purposes of sacrifice. It is but rarely that it bears any acorns, and when it does they are bitter: no animal will touch them, with the sole exception of swine, and not even they, if they can get any other food. An additional reason also for its exclusion from all religious ceremonials, is the circumstance that the fire is very apt to go out in the middle of the sacrifice when the wood of it is used for fuel.