JUNE 28, 1872. THE BUILDING NEWS. 519
to ascertain the effects of lead placed, as was fre-
quently done, between the joints of cut stone
columns, &c., with the object of distributing the
stress uniformly over the beds of the stone. The
experiments were made upon circular blocks of
Bath stone (Box Ground and bottom bed Corsham
Down), 3ft. long by 10}in. and 15in. diameter, or
one set twice the area of the other, the lead being
cut 2in. less in diameter than the beds of the stones
themselves. “The results pointed to the conclusion
that lead so placed between the beds of the stones
reduced the bearing strength of a column to con-
siderably iess than that of a column of only half
its sectional areain which the stones were completely
bedded. On examining the sheets of lead used in
‘the joints, they seemed to have been under compression
at avery few points only, and not to have in any way
tended to equalise the pressure over the area of the
joints. These experiments also seemed to indicate
that raking out the joints of cut stonework, to save
‘the arrises in case of any compression of the joints,
when bedded in mortar, should not be carried too
far. Such questions were, at any rate, worth
‘investigation. In allexperiments upon stone it was
essential to know the exact description of the stone,
the quarry it came from, and, if possible, the parti-
cular bed in the quarry. The time the specimen
‘had been quarried should be stated, as some stones
when green would stand very little stress, but
hardened considerably, in a longer or shorter time,
when exposed to the air. If the specific gravity, or
weight per cubic foot, of the specimen were given, it
would afford some clue to the state of the specimens
experimented on.
CONCRETE.
Before leaving the subject of stone, the author
referred to what he regarded as an artificial stone,
widely used in the present day, viz., concrete. He
thought his hearers would agree with him that a
series of carefully-made experiments on the strength
of different kinds of concrete would be of great
value, under varying conditions, as to the nature of
the lime and cement used, the description of ballast,
proportion of large and small stuff, and mode of
mixing. With good Portland cement, well-burnt
and well-ground, he should use with confidence
for ordinary foundations 12 of ballast to 1 of
cement, provided he was sure of its being properly
mixed; but with ordinary workmen, not properly
drilled in mixing the materials, 10 to 1 would
probably be more advisable. It would be well to
know how much the strength of concrete was
affected by the different modes of mixing in vogue.
For his own part, he should insist upon the mixing
being performed as follows:—A yard measure to be
half filled with ballast, then the measure of cement
to be added, and the yard measure filled up to
the top with ballast. On removing the measure, the
ingredients get partly mixed, and the cement did
not get blown about so much as when placed at the
top of the heap; it should then be turned over twice
‘dry, and shovelled into a third heap, each shovelful
being sprinkled from the fine rose of a watering-can
as it was thrown on the heap, whence it may then
be removed to the trenches. Captain Seddon here
exhibited a block of concrete which had been broken
witha pick out of a newly-built dock wall, in which
12 to 1 Portland cement concrete, mixed in
‘the manner described, was employed, and he thought
it was strong enough for any foundations. In
making experiments the mixing should be done in
‘bulk, at least half a yard cube being mixed at a
time, and not in small quantities, which were more
carefully prepared than would be the case in prac-
tice, and the blocks should be at least 12in. cube.
MORTARS.
Passing from concrete to mortars, the results of
some experiments made for the Patent Selenitic
Mortar Company showed that in mortar made with
common stone lime—Burham or gray chalk lime,
similar to Dorking lime, was used—3 of sand
made a stronger mortar than only 2 of sand, and
stronger again than 4 of sand, which was
probably due to 3 to 1 being about the point
at which more sand would weaken the cohesive and
and adhesive properties of the mortar to a greater
extent than its setting or hardening would be pro-
moted by increasing its porosity. With selenitic
mortar, 5 of sand was the best mixture to resist
thrust; then 4, then 6 of sand; but for adhesion
and to resist tensile stress, 4, and then 6, and
then 5 of sand. From which it was to be
gathered that 3 to 1 was the best proportion of
sand to stone lime in common mortar, and 6 to
1 in selenitic mortar, since the latter gave a
mortar possessing double the strength of common
stone lime mortar. However, in using the selenitic
mortar at Chatham lately, 6 to 1 was not found
to 1, which was being now used. Although the
6 to 1 mortar set very hard, it was so ‘* short”
that it took longer to work, the loss of time out-
weighing the saving of sand. The proportions now
being used were 4 to 1 for exterior work, and
5 to 1 in the body of the walls. Mr. Street
had, the author believed, had some further experi-
ments made with the selenitic mortar in connection
with the new Law Courts.
THE BEST MEANS OF ADDING TO OUR KNOWLEDGE
OF BUILDING MATERIALS,
In concluding his paper, Captain Seddon proceeded
to consider the best means of adding to our know-
ledge of building materials, and the placing of such
knowledge on a firm and unassailable basis. He
said: I think it will be admitted that, in a matter
so important to all as the possession of accurate
information with regard to the strength and pro-
perties of building materials, all who have it in their
power should do their utmost to further the carrying
out of a carefully conducted series of experiments
on an exhaustive scale, in order, if possible, once
and for ever to clear away all doubts and doubtful
theories. It was because I felt that the members of
this Institute were, above all others, most deeply
interested in the prosecution of such experiments,
because I knew how much depended on their united
action in this matter, and that, were they each and
all to assist, the whole question would soon be put
upon avery different footing, that I undertook to
read this paper here to-night. Means for carrying
out a complete series of experiments are placed
within our reach, and of a description which I firmly
believe leaves nothing to be desired. Having often
had occasion to visit Mr. Kirkaldy’s testing works
at Southwark, I have been struck with the immense
advantage which a public—I might almost say a
national—testing apparatus, open to all, such as he
has provided, has over all private efforts, however
numerous. I am perfectly aware that attempts have
been made to detract from the merits of the machine
designed and erected by Mr. Kirkaldy. Prejudice
and self-interest are always to be found arrayed
against anything new, however successful it may
be, in addition to which a certain amount of opposi-
tion is always to be expected from the machine
refusing to give results consistent with the theories
or interests of those who are consulting the oracle.
Different experimenters with different objects in
view, different modes of conducting and recording
the experiments, different kinds of apparatus em-
ployed, often unscientifically constructed and erring
in opposite directions, must, perforce, give different
results, especially when recorded facts are read by
the light of preconceived theories. On the other
hand, we have a single observer of facts, with a
life-long training to the work, systematically re-
cording the results given by a machine of most
perfect construction, capable of testing materials in
large masses, far beyond anything previously at-
tempted. Such an experimenter, who has made it
the study of his life, is far more capable of recording
and comparing facts with accuracy than one who
has had no previous experience at such work, A
comparison of the results obtained by different ex-
perimenters with the same machine, even, is generally
a hopeless task, from the absence of any uniform
system of recording facts or conditions, such as the
temperature, dryness, or exact nature of the speci-
men; if wood, from what part of the tree, and
where grown; if iron, the alteration in form, &c.;
if stone, the quarry, part of quarry, time since
quarrying, Ge. I look upon Mr. Kirkaldy, silently
but powerfully working day by day ina special
field of knowledge, collecting and comparing facts,
as one of the great levers always at work to assist
the progress of scientific knowledge. It is by men
like him that the world at large is constantly being
benefited, though too often without acknowledging
their benefactors; by men who, perceiving a great
want, and the means of supplying it, devote the
whole of their energies to proving the truth of the
ideas they are impressed with, and persevere in
working them out to a successful issue. If all the
members of this Institute, especially those who have
large works on hand, were to cause but a few ex-
periments to be made, in a short time numberless
facts would be collected and compared. and the
range of our knowledge of building materials would
be rapidly extended.
The question naturally arises, who is to pay for
the experiments suggested—the builder, the archi-
tect, or his client? The answer is, neither of the
three, but the manufacturer or producer of the
material. For instance, let us take stone. On any
large work being projected, stone-merchants and
quarry-owners, without number, press the rival
claims of their different stones upon the architect.
to give such good practical results as 4 and 5 | Well, let all who wish to supply the material for the
work send in specimens to Mr. Kirkaldy’s works,
say three 6in. cubes, three blocks 6in. by 6in. by
12in., and three 6in. by 6in. by 18in. Here you
have the material at once to make experiments on,
the cost of which would be defrayed by the success-
ful competitor. Of course, in the case of stone, the
selection would not depend solely upon the results
of experiments on the strength of the material, since
its weathering properties, &c., would have also to be
considered. It may be said that only well-seasoned
and prepared blocks would be submitted. This
could either be met by the architect employing some
one at the quarry to select the stones out of which
to cut the specimens, or by seeing that the stone
supplied come up to the standard of the specimens
submitted for testing. Such a system as this could
be applied to all classes of materials, and the cost
of the experiments would fall on the proper
shoulders. It might possibly be as wellif a com-
mittee of this Institute were to lay down, in con-
sultation with Mr. Kirkaldy, the information which
ought, in each kind of material, to be recorded; and
if they were, as far as possible, to circulate amongst
the members instructions with regard to the number
and sizes most desirable for the specimens of various
kinds of materials to be experimented upon. If some
such course as that suggested were acted upon by
all the members of this Institute, and by the Civil
Engineers as well, before long a vast number of
experiments would place all disputed points beyond
the regions of doubt and uncertainty; we should
hear of fewer failures, and avoid endless little
troubles which are never heard of as failures,
though in strictness they should be so classed,
just as much as those which lead to serious
results. In conclusion, I can only say that if seeing
assists believing, any gentlemen who take an interest
in the subject I have been dealing with this evening,
and who have not seen Mr. Kirkaldy’s testing appa-
ratus, would, I am sure, be amply repaid by a morn-
ing or afternoon spent in watching it doing its
work ; and I feel convinced that they will come away,
unless they have a rival machine of their own,
satisfied that it is capable of supplying with accuracy
all the information they are likely to ask for. As I
have already stated, one of the most important
points tomy mind is, as it were, the public character
of the works, open to all comers and all materials,
and containing complete and accurate records of
experiments made with no aim or object but of
truthfully recording facts. I think that such an
institution ought hardly to be left to the unaided
enterprise of a single individual. I look upon its
success as a matter of national importance, greatly
affecting the safety as well as the pockets of the
public at large, whether sitting in their houses,
whirling along on railroads, or crossing the seas in
ships. Numberless lives are year after year lost,
lifelong miseries caused, and thousands upon
thousands of pounds wasted, from a want of proper
knowledge of the strength and properties of building
materials.
DISCUSSION.
The discussion upon the paper took place at the
meeting of the Institute on the 27th ult., the Pre-
sident, Mr. T. H. Wyatt, in the chair. With refer-
ence to selenitic mortar, Major-General Scorr said
that in dealing with limes and cements he had found
by experiment in the case of pure limes that they
were not dealing with a material like hydraulic
limes. The setting properties of pure limes were
due to the action of the carbonic acid gas, but in
hydraulic limes the converse of this was true.
While the pure limes owed their setting properties
to the action of the atmosphere, the hydraulic limes
owed theirs to the action of the water. Between
these extremes all varieties of lime were found,
owing their setting partly to the atmosphere and
partly to the water.—The Prestpenr said that he
had wished to try the selenitic process in connection
with concrete, but the builder had objected that
concrete so made would not set in the bottom of the
trench.—Major-General Scorr said that what the
builder might have regarded as “setting” was
really only the first slaking and warming of the lime.
If it had been examined after a month or so, the re-
sult would have been astonishing.—Professor Kerr
referred to a plan he had seen adopted, viz., the
mixing of lime and ground chalk in certain propor-
tions, and then adding a very large proportion of
sand—he thought four or five times the quantity of
the lime and chalk combined. It was considered
that the carbonic acid gas was communicated from
the chalk to the mortar, the induration and setting
being very quick. He had seen mortar produced
in this way which was equal in strength and appear-
ance to Portland stone.—Captain Srppon said, with
reference to selenitic mortar, he had found in works
at Chatham that notwithstanding the large admix-
ture of 6 parts sand to 1 of lime, the results
