DOI Page / Citation link:
https://doi.org/10.11588/diglit.1312#0029
16 THE GREAT EXHIBITION
decayed, and substituting sound timber in its place. Various plans have, from time to
time, been adopted with the view of preventing the great loss thus sustained. Some
of these processes we will mention, inasmuch as they were practically illustrated by spe-
cimens exhibited; but, before doing so, it may be as well to say a few words on the
cause of this rotting and decay of wood, and the principle on which the remedy is founded.
All wood contains what is called albumen, an essential ingredient in vegetable bodies,
entering largely into the composition of the sap, or what we may term the life-blood
of the tree, which circulates through the system. As long as this albumen is supplied,
with sufficient moisture to retain it in a soluble condition, so long will it be liable to en-
ter into a kind of fermentation, especially if placed in damp or ill-ventilated situations, and
often even where the ventilation is perfect, and. the atmosphere in its ordinary state of
humidity. If a piece of green timber—that is, timber recently felled, and therefore con-
taining this albumen in a perfect state of solution, in the moisture of the wood—be em-
ployed in the construction of a house, the albumen undergoes fermentation, and the rot
and decay of the wood speedily follows. The fermented albumen affords a food highly
relished by a certain class of microscopic insects, whose keen perception soon leads them
to find out its presence. These penetrate the wood in all directions, in search of this
food ; and, in so doing, make innumerable small crevices in the wood, through which air
and moisture enter. These combine with the nitrogen of the fermenting albumen, and
cause a formation of an ammonia and its compounds, which, favours the growth of the
seeds of numerous microscopic plants, which are ever floating in the air, seeking a
suitable resting-place where they may fulfil the functions assigned them of continued
increase. The minute plants which spring up from these seeds, in their endeavours to
reach the light, push their way through the fibres of the softened wood, until at last, by
the combined agency of animal and vegetable life, the timber rots, crumbles away, ana*
becomes unfit for further use either in buildings or utensils.
How is this waste and destruction of wood to be prevented ? To a certain extent
by thoroughly drying the timber in a current of air. This, however, takes considerable
time to effect: for instance, a large piece of oak requires exposure for eight or ten years
to dry it completely. This is demonstrated by the fact that it continues to lose weight
for that period. We may apply heat to hasten the process of drying; but the wood,
when exposed to the ordinary temperature of the atmosphere, absorbs moisture in quantity
varying with the compactness of the wood. In a dry room, without a fire, the quantity
of water re-absorbed by wood amounts, on an average, to ten per cent. As long as the
albumen of the wood is supplied with sufficient moisture to render it soluble, so long will
there be danger of dry-rot. The best plan, therefore, to adopt is, to render this albumen
permanently insoluble, so that, however much moisture shall be absorbed, it cannot be
brought into an active state again. For this purpose, Sir H. Davy recommended that
the wood should be steeped in a solution of corrosive sublimate, a salt called bichloride
of mercury by chemists, which has the property of forming an insoluble compound with
the albumen, and thus preventing its further action. This process was commercially
applied by Mr. Ryan; but from the expensiveness of the preparation, and the fear that
the use of this poisonous salt might prove deleterious to the health of sailors inclosed
within their wooden walls, as well as to persons residing in houses filled up with this
prepared timber, the employment of corrosive sublimate has been abandoned. In
Class IV., Mr. Bethell exhibited some specimens of timber, saturated with the creosote
oil, obtained from wood and coal-tar. This is a very powerful preservative; but possesses
the disadvantage of imparting a disagreeable odour, and increased inflammability to the
wood. Mr. Payne exhibited specimens, prepared first by injecting a soluble salt of baryta
into the pores of the wood, and then adding solution of sulphate of iron; by this means a
decayed, and substituting sound timber in its place. Various plans have, from time to
time, been adopted with the view of preventing the great loss thus sustained. Some
of these processes we will mention, inasmuch as they were practically illustrated by spe-
cimens exhibited; but, before doing so, it may be as well to say a few words on the
cause of this rotting and decay of wood, and the principle on which the remedy is founded.
All wood contains what is called albumen, an essential ingredient in vegetable bodies,
entering largely into the composition of the sap, or what we may term the life-blood
of the tree, which circulates through the system. As long as this albumen is supplied,
with sufficient moisture to retain it in a soluble condition, so long will it be liable to en-
ter into a kind of fermentation, especially if placed in damp or ill-ventilated situations, and
often even where the ventilation is perfect, and. the atmosphere in its ordinary state of
humidity. If a piece of green timber—that is, timber recently felled, and therefore con-
taining this albumen in a perfect state of solution, in the moisture of the wood—be em-
ployed in the construction of a house, the albumen undergoes fermentation, and the rot
and decay of the wood speedily follows. The fermented albumen affords a food highly
relished by a certain class of microscopic insects, whose keen perception soon leads them
to find out its presence. These penetrate the wood in all directions, in search of this
food ; and, in so doing, make innumerable small crevices in the wood, through which air
and moisture enter. These combine with the nitrogen of the fermenting albumen, and
cause a formation of an ammonia and its compounds, which, favours the growth of the
seeds of numerous microscopic plants, which are ever floating in the air, seeking a
suitable resting-place where they may fulfil the functions assigned them of continued
increase. The minute plants which spring up from these seeds, in their endeavours to
reach the light, push their way through the fibres of the softened wood, until at last, by
the combined agency of animal and vegetable life, the timber rots, crumbles away, ana*
becomes unfit for further use either in buildings or utensils.
How is this waste and destruction of wood to be prevented ? To a certain extent
by thoroughly drying the timber in a current of air. This, however, takes considerable
time to effect: for instance, a large piece of oak requires exposure for eight or ten years
to dry it completely. This is demonstrated by the fact that it continues to lose weight
for that period. We may apply heat to hasten the process of drying; but the wood,
when exposed to the ordinary temperature of the atmosphere, absorbs moisture in quantity
varying with the compactness of the wood. In a dry room, without a fire, the quantity
of water re-absorbed by wood amounts, on an average, to ten per cent. As long as the
albumen of the wood is supplied with sufficient moisture to render it soluble, so long will
there be danger of dry-rot. The best plan, therefore, to adopt is, to render this albumen
permanently insoluble, so that, however much moisture shall be absorbed, it cannot be
brought into an active state again. For this purpose, Sir H. Davy recommended that
the wood should be steeped in a solution of corrosive sublimate, a salt called bichloride
of mercury by chemists, which has the property of forming an insoluble compound with
the albumen, and thus preventing its further action. This process was commercially
applied by Mr. Ryan; but from the expensiveness of the preparation, and the fear that
the use of this poisonous salt might prove deleterious to the health of sailors inclosed
within their wooden walls, as well as to persons residing in houses filled up with this
prepared timber, the employment of corrosive sublimate has been abandoned. In
Class IV., Mr. Bethell exhibited some specimens of timber, saturated with the creosote
oil, obtained from wood and coal-tar. This is a very powerful preservative; but possesses
the disadvantage of imparting a disagreeable odour, and increased inflammability to the
wood. Mr. Payne exhibited specimens, prepared first by injecting a soluble salt of baryta
into the pores of the wood, and then adding solution of sulphate of iron; by this means a