[Illustration:
SKETCH OF DRY ROT FUNGUS
_On basement floor joist in house, at Greenwich, near London Feb 1875._
END OF JOIST
_Crumbled into fine red powder, with slight rubbing._
TOP OF JOIST.
_Portion of fungus near the edge was torn away on removal of floor
boards, the undersides of which were covered with fungus, as well as the
sides of nearest joist 10ins. distant._
_Portion of fungus near the edge was torn away on removal of joist.
Fungus covered top and sides of sleeper joist._
_Colours of fungi. White, yellow, green, purple, and rusty red._]
A TREATISE
ON THE
ORIGIN, PROGRESS, PREVENTION, AND CURE
OF
DRY ROT IN TIMBER.
WITH REMARKS ON
THE MEANS OF PRESERVING WOOD FROM DESTRUCTION BY
SEA WORMS, BEETLES, ANTS, ETC.
BY
THOMAS ALLEN BRITTON,
LATE SURVEYOR TO THE METROPOLITAN BOARD OF WORKS, AND SILVER
MEDALLIST OF THE ROYAL INSTITUTE OF BRITISH ARCHITECTS IN 1854,
1856, AND 1870.
[Illustration]
LONDON:
E. & F. N. SPON, 48, CHARING CROSS.
NEW YORK: 446, BROOME STREET.
1875.
THIS VOLUME
IS
Dedicated to
GEORGE VULLIAMY, ESQ.,
VICE-PRESIDENT
OF THE
ROYAL INSTITUTE OF BRITISH ARCHITECTS;
AND
ARCHITECT
OF
THE METROPOLITAN BOARD OF WORKS;
AS A SLIGHT ACKNOWLEDGMENT
OF HIS
COUNSEL, SYMPATHY, AND FRIENDSHIP,
DURING MANY YEARS.
PREFACE.
In preparing this treatise on Dry Rot, the author has endeavoured
to place in as condensed a form as was consistent with the nature
of the subject, the knowledge and information dispersed through a
numerous collection of writers who have treated thereon; he has also
availed himself of the assistance of professional friends, builders,
timber-merchants, foremen and carpenters; and, by so doing, has been
enabled to record several instances of the progress and cure of dry
rot. He has consulted many valuable papers published during the last
thirty years, in the various professional journals in England, America,
France, and Germany, upon this important subject, and has also obtained
much useful information from the works of Evelyn, Nicholson, Tredgold
by Hurst, Papworth, Burnell, Blenkarn, and other English writers upon
timber; Silloway, of North America; Porcher, of South America; Du Hamel,
De Moray, and De Lapparent, of France; and several writers whose works
will be referred to.
It is many years since a separate and complete work on dry rot has been
published, and those who are desirous of inquiring into the matter are
frequently at a loss where to obtain any information. Existing works on
the subject are out of print, and although they can be seen at a few
professional institutes, they are beyond the reach of the general public.
It has been the aim of the author in preparing this treatise to give a
fair hearing to every patentee, and he has endeavoured to be as impartial
as possible in recording instances of failure and success. If he has
erred in any particular case, he will be happy, should this work reach a
second edition, to make any necessary correction.
The reader will probably find some things repeated in the course of the
work; this is in many cases unavoidable, and in some advisable; for if by
a little tautology important truths can be impressed upon the mind of the
reader, the author will feel that his labour in preparing this work has
not been altogether in vain.
Modern authorities have been relied upon in preference to ancient ones:
the following sentence, written by the late Sydney Smith, is quoted as a
reason for so doing:
“Those who come first (our ancestors) are the young people, and have the
least experience. We have added to their experience the experience of
many centuries; and, therefore, as far as experience goes, are wiser, and
more capable of forming an opinion than they were.”
20, LIMES GROVE, LEWISHAM,
_May 14th, 1875_.
CONTENTS.
CHAPTER I.
On the Nature and Properties of Timber Page 1
CHAPTER II.
On the Gradual Rise and Development of Dry Rot 14
CHAPTER III.
On Felling Timber 51
CHAPTER IV.
On Seasoning Timber by Natural Methods, viz. Hot and Cold Air;
Fresh and Salt Water; Vapour; Smoke; Steam; Boiling; Charring
and Scorching, &c. 63
CHAPTER V.
On Seasoning Timber by Patent Processes, &c. 105
CHAPTER VI.
On the Means of Preventing Dry Rot in Modern Houses 171
CHAPTER VII.
On the Means of Preservation of Wooden Bridges, Jetties, Piles,
Harbour Works, &c., from the Ravages of the _Teredo navalis_ and
other Sea-worms 203
CHAPTER VIII.
On the Destruction of Woodwork in Hot Climates by the _Termite_
or White Ant, Woodcutter, Carpenter Bee, &c.; and the Means of
Preventing the Same 240
CHAPTER IX.
On the Causes of Decay in Furniture, Wood Carvings, &c.; and the
Means of Preventing and Remedying the Effects of such Decay 262
CHAPTER X.
Summary of Curative Processes 283
CHAPTER XI.
General Remarks and Conclusion 288
INDEX 295
ILLUSTRATIONS.
DRY ROT ON FLOOR JOIST _Frontispiece_
_To face page_
TIMBER BEAMS--ROTTEN AT THE HEART 34
BALTIC MODES OF CUTTING DEALS 64
MR. KYAN’S TIMBER PRESERVING TANK 126
MESSRS. BETHELL AND CO.’S TIMBER PRESERVING APPARATUS 136
TIMBER PILES FROM BALACLAVA HARBOUR 208
DESTRUCTION OF TIMBER PILE BY TEREDO 212
SHELL AND CELL OF TEREDO NAVALIS 216
PILES, SOUTHEND PIER; LIMNORIA, &C. 220
CARPENTER BEES AT WORK 260
A TREATISE ON DRY ROT IN TIMBER.
CHAPTER I.
ON THE NATURE AND PROPERTIES OF TIMBER.
In considering the subject of Timber trees, we commence with their
Elementary Tissues, and first in order is the _Formative Fluid_, which
is the sole cause of production of every tissue found in trees. It
is semi-fluid, and semi-transparent, and in this condition is found
abundantly between the bark and the wood of all trees in early spring;
and thus separates those parts so as to permit the bundles of young wood
to pass down from the leaves, and thus enable the tree to grow. It is
under these conditions that the woodman strips the bark from trees which
are to be cut down, since then it does not adhere to the wood.
The first step in the formation of any tissue from the formative fluid
is the production of a solid structureless fabric called _Elementary
Membrane_, and a modification of that fabric termed _Elementary Fibre_.
The structures which are produced from the above-mentioned “raw
material” are very varied in appearance, and are called _Cellular
Tissues_, to signify that they are made up of hollow cells. The spaces
between the cells are called _Intercellular Spaces_, which are of vital
importance, as they contain air. _Woody fibre_ constitutes the mass of
the stems of our forest trees. Its peculiar characteristic is that of
great tenacity, and power of resistance, and for this its structure is
admirably adapted: it consists of bundles of very narrow fibres, with
tapering extremities, and is so placed from end to end, that the pointed
ends overlap each other. Each fibre is very short, and the partitions
which result from the apposition of the fibres, end to end, do not
interfere with the circulation through them. The tube is not composed
of simple thin membranes only; but in addition has a deposit within it,
which, without filling the tube, adds very greatly to the strength of
the fibre: an arrangement whereby the greatest strength and power of
resistance and elasticity shall be obtained; and, at the same time, the
functions of circulation uninterruptedly maintained. The strength is
mainly due to the shortness of each fibre, the connection by opposite
ends of many fibres, almost in one direct line, from the root upwards;
and lastly, to the deposit on the inner side of the membrane. The uses
of woody fibre are very varied and most important; it is the chief organ
of circulation in all wooded plants, and, for this purpose, pervades
the plant from the root to the branches. The current in this tissue
is directed upwards from the shoot, through the stem to the leaves,
and downwards from the leaves through the bark to the root. Thus, its
current has a twofold tendency; the ascending and chief one being for
the purpose of taking the raw, or what is called the _common sap_, from
the ground to be digested in the leaves, and the descending being devoted
to the removal from the leaves of the digested, or what is termed the
_proper sap_, to be applied to the purposes of the tree, and also of the
refuse matter to be carried to the roots, and thence thrown out into the
soil as a noxious material. The _proper sap_ differs considerably in
different trees; it is always less liquid, and contains a much greater
proportion of vegetable matter than the common sap. It is very probable
that trees of the same kind produce proper sap of different qualities in
different climates.
WOODY FIBRE may be considered the storehouse of the perfected secretions.
It is well known that as trees advance in life, the wood assumes a darker
colour, and more particularly that lying near to the centre of the stem.
This is due to the deposit of the perfected juices in the woody fibre at
that point; and where age has matured the tree, it is probable that the
woody fibre so employed is no longer fitted for the circulation of the
sap; and, also, that the perfected sap, when once deposited, does not
again join in the general circulation. The dark colour of the heart of
oak, as contrasted with oak of very recent growth, is an illustration
of this fact, as is also the deep colour which is met with in ebony and
rose-wood. Technically, the inner wood is called the heart-wood, and the
outer or younger wood the sap-wood. Of these, the former contains little
fluid, and no vegetable life, and, being the least liable to decay, is
therefore the most perfect wood; the latter is soft and perishable in
its nature, abounding in fermentable elements; thus affording the very
food for worms, whose destructive inroads hasten its natural tendency to
decay.
The proportion of sap-wood in different trees varies very much. Spanish
chestnut has a very small proportion of sap-wood, oak has more, and fir a
still larger proportion than oak; but the proportions vary according to
the situation and soil, and according to the age at which they have been
felled: for instance, the teak tree in Malabar, India, differs from teak
in Anamalai, South India. This subject has been very fully treated by Mr.
Patrick Williams, in his valuable work on Naval Timber.
WOODED STEMS are divided into two great and well-defined classes,
according to their internal conformation, viz. such as grow from without
(exogenous), and such as enlarge from within (endogenous). The former are
more common in cold, and the latter in hot climates.
EXOGENOUS STEMS.--On examining a section of a stem of an oak, or any
other of our forest trees, we observe the following parts: first, the
pith, or its remains in the centre; second, the bark on the outside;
third, a mass of wood between the two, broken up into portions by the
concentric deposition of the layers, and by a series of lines which
pass from the centre to the circumference. Thus, there are always pith,
bark, wood, and medullary rays. Each stem has two systems, the cellular
or horizontal, and the vascular or longitudinal, and the parts just
mentioned must belong to one or other of those systems. Thus, the pith,
medullary rays, and bark belong to the horizontal system; and the wood
constitutes the longitudinal system.
THE PITH occupies the centre of the stem, and remains throughout the
period of growth of some trees, as of the elder; or is abstracted after
a few years, as in the oak, and almost all large trees. In the latter
class of trees, there are some remains of the pith for many years after
the process of absorption has commenced, but at length no vestige can
be detected, and its position is known only by the central spot around
which the wood is placed in circles. In the old age of the tree the pith
frequently assumes a colour which it has obtained from the juices which
have been deposited. The connections of the pith are extremely important.
Firstly, it is in direct connection with every branch, and is the
structure which first conveys fluids to, and receives fluids from every
new leaf. It thence becomes the main organ of nutriment, and, at the same
time, the chief depository of the secretions. Secondly, it is in equally
direct and unbroken connection with the bark, through the medium of the
medullary rays; and so becomes the centre of all the movements of sap
which proceed in the horizontal system.
The mode in which the ultimate disappearance of the pith occurs has been
a matter of speculation. That the circulation in the heart-wood ceases
after a certain number of years, and that the connection between it and
the bark becomes broken, is proved by the fact that numbers of trees
may be found in tolerably vigorous growth within the bark, whereas at
the heart they are decayed and rotten. It appears clear that it is not
converted into wood, and there are facts against the opinion that it
is gradually compressed by the wood; but since it is known that in the
growth of the tree much compression of the previously formed wood must
occur, and since this compression is a likely theory by which to account
for the disappearance of the less resisting pith, it is now generally
considered to be one of the causes of this occurrence. As a general rule,
the pith, so long as it exists, is not mingled with other than cellular
structures; but, in certain instances, wooden fibre has been found with
it, and, in others, spiral vessels have been detected.
MEDULLARY SHEATH.--Immediately surrounding the pith of all exogenous
plants, there is a layer of longitudinal tissue, which has received
the name of medullary sheath. This sheath has no special walls, but is
bounded by the pith on the inner, and the wood on the outer side. It is
in this situation that ducts of various kinds and spiral vessels may be
found, and in all cases it conveys the longitudinal structure from the
root, direct to each leaf. The integrity of this structure is therefore
highly necessary to the life of the tree.
MEDULLARY RAYS.--These structures come next in order, and, as has been
previously intimated, belong to the horizontal cellular system of the
stem; they constitute the channel of communication between the bark and
the pith, and are composed of a series of walls of single cells resting
upon the root, and proceeding to the top of the tree, and radiating from
the centre. They lie between the wedge-like blocks of wood, and as they
have a lighter colour than the wood, they are evident on an oblique
section of any stem, and are called the silver grain. Their colour and
number suffice to enable anyone to distinguish various kinds of wood, and
greatly increase their beauty. They cannot, of course, exist before the
wood is formed, and are therefore not met with in very young trees. They
commence to exist with the first deposited layers of wood, and continue
to grow outwardly, or nearest to the bark, so long as the wood continues
to be deposited. In those woods which possess in abundance the silver
grain, another source of ornament exists, viz. a peculiar damask or
dappled effect, somewhat similar to that artificially produced on damask
linens, moreens, silks, and other fabrics, the patterns on which result
from certain masses of the threads on the face of the cloth running
lengthways, and other groups crossways. This effect is observable in a
remarkable degree in the more central planks of oak, especially in Dutch
wainscot.
THE BARK.--As the medullary rays terminate in the bark, on their outer
side, the consideration of that part next follows. It forms the sheath
of the tree, and its more immediate use is that of giving protection to
the wood. If bark did not exist, there would be no formative fluid, and
without formative fluid there could not be any deposit of woody fibre.
WOOD.--We find wood occupying nearly the whole body of the trunk of the
tree, and arranged, as a rule, in a very regular manner. On taking up
any piece of wood, but more particularly the entire section of a stem,
we first notice a series of circles, which increase in diameter and
separate by wider intervals as we approach the bark. In this manner the
trunk is composed of numerous zones enclosed within each other. Again,
in almost all trees, the medullary rays before mentioned may be observed
passing in straight lines from the centre to the circumference; and, as
the circle of the stem at the bark is much larger than any circle near to
the centre, it follows that the medullary rays will be wider apart at the
bark than at the pith. On this view of the subject it may be stated that
the stem is composed of a series of wedge-shaped blocks, which have their
edges meeting at the centre. The combination of these two views gives the
correct idea of the arrangement of the wood, viz. a series of wedges,
each divided into segments of unequal width by circular lines passing
across them. From this description it must not be imagined that these
various portions are detached from each other; for although the medullary
rays and the circular mode of deposition both tend to a less difficult
cleavage of the wood, they yet bind the parts very closely to each other.
The explanation of the occurrence of distinct zones of wood is, that each
zone is the produce of one year, and that in our climate, more so than in
tropical climates, the period of growth of wood ceases for many months
between the seasons, and this induces a distinction in appearance between
the last wood of a former, and the first wood of a succeeding year. This
distinction is maintained throughout each year, and throughout a long
series of years.
The enclosure of zone within zone, is owing to the mode in which the wood
is produced, and the position in which it is deposited. Wood is formed by
the leaves during the growing season, and passes down towards the root
between the bark and the wood of the previous year; and, as the leaves
more or less surround the whole stem, the new layer at length completes
a zone, and perfectly encloses the wood of all former years. This is
the explanation of the term exogenous, which is derived from two words
signifying to grow, outwardly, for the stem increases in thickness by
successive layers on the outer side of the previously formed wood.
The thickness of the zone for the year is rarely equal around the whole
circumference of the stem, and this is due to the lesser abundance
of leaves on the branches of one side than on the other, or to the
prevalence of winds, or some other physical cause, acting in that
direction in opposition to the growing process. It should be observed
that there is not in timber any appearance of a gradual change from
alburnum to perfect wood. On the contrary, in all cases the division is
most decided; one concentric layer being perfect wood, and the next in
succession sap-wood.
The age of trees has been inferred, when a section of the whole stem
could be examined, by counting the number of rings of wood which have
been deposited around the pith. In tropical countries, however, this
method cannot be always relied upon.
Woods are variable in quality according to the nature of the climate, and
of the soil, as also in a considerable degree to the aspect in which they
are situated. Trees grown slowly in open, dry, and exposed situations
are more fine and close in their annual rings, and more substantial
and durable, than those which are grown in close and shady forests, or
rapidly reared in moist or sappy places, the latter being soft and broad
in their rings, and very subject to decay; and their pith is not always
quite in the centre, for the layers are variable also.
The waggon maker takes care to combine toughness and durability by
selecting his wood from trees of second growth, or from trees of first
growth that from infancy have stood alone, or far apart. If the soft wood
trees have stood alone, and are very large (as is often the case with
some of the pines), and most of the branches are near the top, the wood
near the base of the trunk is sometimes found to be _shaky_. This defect
is produced by the action of heavy winds on the top of the tree, which
wrenches or twists the butt, and thus cleaves apart the fibres of the
wood. If the main-top (_couronnement_, of French writers) of a tree dies
while the tree is yet standing, it indicates that water has found its way
into the trunk, and that the tree is in a state of decay.
The fir which grows on very dry marl, forms very narrow yearly rings; if
on rich or damp marl, they are wide; and when on wet soil, they are again
smaller. The common fir on moor soil, has even smaller yearly rings than
if on dry sand or marl. From this it is evident that too wet or too dry a
soil is not suitable for this tree.
The alder and the willow grow best on wet soil, and thrive but poorly
when standing dry.
The weight of wood is of great importance, because its hardness,
resistance, and its heating power, as well as other valuable properties,
are all more or less depending upon it. In the first place, we must
consider that even wood which has been forested very light will become
heavy, when put for some time into water, but in such timbers the sap is
already given to dissolution. If the fibre were the only substance in
the wood, then the specific weight would depend upon the number of pores
contained in its body; the pores are, however, filled with a substance
such as resin, die, &c. Some years since, when the Indian railways
were being formed, the native wood-cutters were so well aware of the
above-mentioned fact, that they used to cut down the soft and inferior
woods in the forests; soak them in water for a certain time; and then
endeavour to pass them to the railway contractors as sound, heavy, and
good railway sleepers, and the latter, not being acquainted with the
Indian woods, were, at first, often deceived.
The hardest, and heaviest woods come from the hotter climates; the only
exception is the pine, which thrives considerably better, and furnishes
heavier timber, when it has grown in colder regions, or upon high
mountains.
Trees grown on northern slopes furnish lighter timber than if grown on
southern or western. The soil has great influence upon the width of the
yearly rings, and from this we are able to come to a conclusion in regard
to the specific weight. In the fir and larch trees the wood is heaviest
when their rings are smallest.
The difference in the strength of timber between the south and the
north side is attributable to the grain being closer on the north side,
as the sap does not rise in the same proportion as upon the south.
In forest-grown wood the difference is almost imperceptible, as the
sun cannot act upon the trunk of the tree; in open-grown timber, the
difference is really perceptible. It is well known that all woods do not
lose strength by being open grown, or, in other words, that the south
side is not always weaker than the north; that theory only applies to
the coniferæ species. In ash it is the opposite, as the south side is
the strongest. In soft-wooded trees, as the acer species, the difference
is not perceptible, as the annual rings, and the intervening cellular
tissues, are so close akin as to render the wood so compact in its grain
that there is no difference in its strength. The coniferæ species, or the
pines, are the only classes of woods that are stronger on the north side
than on the south: it is well known that the difference originates in the
wood being more open in the grain on the south side than on the north.
An influence upon the specific weight is exercised by the resin, and
the die, which are contained in the interior of the wood. On level dry
ground, or deep sandy soil, we find the fir beautifully red inside;
but when we look at it on lias soil, it shows broad yearly rings, and
hardly any colour at all. The larch tree, again, in such soil, develops
itself well with a rich colour. The cause for these appearances must
therefore rest with the chemical condition of the soil, and its effect
upon the individuality of the fir: it is probably the nature of the soil
that causes the difference of character between Honduras and Spanish
mahogany; Honduras being full of black specks, and Spanish of minute
white particles, as if it had been rubbed over with chalk. Oaks generally
furnish good timber when grown slowly in dry ground, whilst those from
wet soil appear comparatively spongy; similar results are obtained with
other trees.
Many persons constantly employed on wood are of opinion that it becomes
harder if it is worked or barked whilst green.
It is not safe to condemn timber, merely because long cracks are visible
on the surface. Such openings are frequently only superficial, and do not
penetrate deeply into the wood: in such cases it is very little weakened
thereby. It is difficult to obtain timber of large scantling without some
defects of this kind, but care should be taken to ascertain if they are
of a serious nature.
Trees arrive at an age when their wood becomes ripe, and then they are
fit for felling; but as upon the proper method and time for doing this,
the prevention of dry rot frequently hinges, a separate chapter is
devoted to this part of the subject.