or decay-blackened wood1 was detected. This, however, was the
solitary instance of such a discovery, and must be set down as very
exceptional. Examination of the substance of the black lines has
been made by more than one specialist with the microscope, but
the observations have failed to disclose much beyond the bare
fact of the organic character of the specimens. Mr. W. M.
Hutchings, of Newcastle, tested a number of samples most care-
fully, but was in no case able to detect anything like a structure.2
Another scientific observer came to conclusions not greatly
One very curious fact has gradually emerged from the sections.
It was observed that the dark line was often found next to and
resting on the stones of the base. Close attention to this point
established this as a normal circumstance in the sections. Why
this should be so the cespiticious theory would leave no doubt.
It is not only the present practice in sod building to lay the sod
with the grass downwards; it is an axiom4 of military sod work,
and it can be proved to be a rule of at least 17th century
standing/' The cespiticious theory would date back that rule
still further, and assign it to Roman antiquity. If our wall is a
wall of sods, what more natural than that the turf should have
been laid with its grassy side below ?
There are some phenomena in the sections not yet fully
1 It may be worth noting that Vitruvius, i. 5, recommends for stone walls
"through-bands" or binding courses of charred olive wood. "In crassitudine
perpetuae talcao oleagineae ustulatae quam creberrime instruantur uti utraeque
muri frontes inter se quemadmodum fibulis his taleis colligatae aeternam habeant
firmitatein." [It is often impossible, except by elaborate analysis, to distinguish
charred from decayed wood, and it is probable that in many cases observers have
included among Roman remains charred wood when the actual substance was
decay-blackened wood. Hence the statements that such and such a Roman house,
or fort, or town, was burnt, must be received with caution. F. H.]
2Mr. W. Maynard Hutchings, of Newcastle-on-Tyne, wrote on 31st May, 1891:—
•"I am not able to give you any information as to origin of the organic matter in
your specimens. I can make out nothing beyond the fact that it is organic."
:!After examining specimens of soils in the vallum, a friend of Mr. Jolly's
wrote :—" As a whole, there is fibre present in the material, but of a very fine
character. It is the remains of fine structures, and much of the original deposit
has doubtless by its decomposition aided in the impregnation of the soil with
4 " Sods are built . . . with the grass downwards." Philips, Article 199.
5 "Pour employer les gazons ... on les applique tout du long, l'herbe
tournee au dessoubz." 17th century manuscript " Traitte des Fortifications,"
penes Mr. Neilson. The practice is evidently, based on experience, and has
doubtless always obtained.