June 21, 1918. .

THE COLLIERY GUARDIAN

1251

before the Royal Commission on Metalliferous Mines
and Quarries, established at once the danger attached
to the inhalation of certain dusts and the compara-
tively innocuous nature of other dusts. Dr. Haldane
had himself supplied the clue which through investiga-
tion of the mortality of flint knappers—the first
investigation of mortality associated with exposure to
a pure dust—demonstrated the particularly harmful
nature of the fine dust of crystalline silica. Follow-
ing up that clue, the mortality among those exposed
to inhalation was found to vary directly with (a) the
amount of pure silica in the dust, and (b) the amount
of exposure to that dust. Thus, granite dust, vhich
was composed of about one-third part of t’liea, was
found to be associated with a lower mortality rate
than that among sandstone masons and others asso-
ciated with exposure to sandstone dust; and further,
no proof could be obtained that fibroid phthisis
occurred among any persons exposed to the inhalation
of a dust which did not contain pure silica. For the
moment the problem then seemed clear, but subse-
quent enquiries had raised most interesting questions.
Thus, as Dr. Haldane had pointed out, Altofts shale,
with a much higher percentage of silica than granite
dust, was not associated with the phthisis mortality
rate of those exposed to its inhalation. The dust of
ganister, which was a pure form of silica, was found
to cause a fearful mortality among those inhaling it
either in the mines or in the brickyards, yet that
mortality was profoundly modified, at any rate among
the makers of bricks, if the ganister were mixed with
fireclay. In that industry there was no stepping-stone
between the terrible mortality among the men who
made ganister bricks which were bonded together with
lime, and the mortality, but little different from
the normal, among those men who made ganister bricks
bonded together with clay. Clay then seemed for the
moment to possess the power of inhibiting the influence
of silica. Further thought, however, showed that
potters exposed to flint dust suffered whether the flint
were mixed or unmixed with pottery clay, thus sug-
gesting that there must be some difference between
fireclay and pottery clay in the inhibitory effect. Dr.
Haldane had now put forward a suggestive explana-
tion which was in some ways on the same lines as one
which he (Dr. Collis) had in mind in 1915, when he
said, “ Certain investigations now being carried on
by Dr. H. C. Ross suggest that this action of clay in
modifying, the influence of silica dust, which appears
to be similar to that exerted by coal, depends on the
presence of certain organic constituents in these
materials.” However future work might show that
certain inhibitory influences could stay the action of
silica dust in producing fibroid phthisis, he felt him-
self at present unconvinced that the evidence before
them was sufficient to establish that any other dust
except that of fine silica had the power of causing
fibroid phthisis. He was of course aware of the work,
to which Dr. Haldane referred, which was being car-
ried on by exposing animals to the dust of emery and
carborundum. Those experiments undoubtedly showed
that the. lungs of the animals exposed were damaged,
but in actual practice there was no evidence that
men exposed to the inhalation of such dusts suffered
from fibroid phthisis or that the lungs of such men
showed the characteristic shadows when radiographed;
and the same thing applied to men exposed to fine
glass dust. He would therefore venture to submit that
the problem before them was a double one. First, how
was it that silica only among the dusts was associated
with a heavy mortality from fibroid phthisis ? Secondly,
how was it that that mortality was profoundly modi-
fied, if not entirely inhibited, when the silica was
combined with certain other materials, notably those
containing certain organic constituents?

Influence of Accelerative Force.

Mr. H. W. G. Halbaum (Cardiff) stated in a written
communication that this was apparently the first time
the theory of alloys considered as solid solutions had
been applied to the problem of the effects of the inhala-
tion of different varieties of dust. He thought that
Dr. Haldane was absolutely right in the position he
had taken up, and had made a distinct step forward
by showing that the principle of “ adsorption,” or the
principle of alloys as solid solutions, applied not only
to metals but to non-metals also. That step seemed
most natural and logical, but it started new trains of
thought for all that. For example, it suggested the
idea of saturation, and that it was possible to overdo
the stone-dust treatment. Would Dr. Haldane say
if that inference were justified? Or did the alloying
action as carried out in the lungs proceed between, say,
argillaceous and arenaceous shales, as well as between
coal dust and siliceous stone dust? The principle
enunciated by Dr. Haldane further suggested that if
the alloying process were to be assisted to the utmost,
the elements of the alloy should approach as nearly
as possible the liquid state. In other words, they
should be as finely divided as practicable in order that
the surfaces of contact per unit of weight should be
a maximum. He would like to know from the author
whether he agreed with that inference or not. Dr.
Haldane had also spoken of the protective action of
the nostrils, and had implied that that protective action
was due to the nostrils acting as a kind of filter or
sieve. But was there not another factor ? The inhala-
tion was simply an accelerative force which acted on
the atmosphere outside, putting the air in motion
and drawing it into the lungs. Now, f=ma where
m = the mass, a = the acceleration, and f = the force
producing the acceleration a in the mass m. Like every
force, /, the force of inspiration, would produce smaller
accelerations in larger masses. Hence it was reason-
able to suppose that, in drawing in air containing solid
matter in suspension, the lighter particles would be
drawn into the lungs more rapidly, owing to their
accelerations being greater than those of the heavier
particles of equal bulk. It would appear, therefore,
that cceteris paribus, in air containing solid particles
of different specific gravities, the nostrils had a selec-
tive capacity as well as a filtering action. Did the
author agree with that? If so, they must conclude

that in considering the suitability of any stone dust
one must take into account not only the specific gravity
of the substance in bulk but the difference of the
specific gravities of its various ingredients also. Dr.
Haldane’s paper went a long way towards proving
what he (Mr. Halbaum) had long believed, viz., that,
to be at once innocuous and efficient, the stone dust
must be as finely divided as possible, and not only
distributed, but also selected, by the air-current. In
other words, the air-current should sustain the same
relationship to the mine and perform the same office,
the same dual office, as the nostrils sustained and per-
formed for the individual.

Prof. W. Galloway wrote that Dr. Haldane’s ex-
planation of the reasons why certain dusts and mix-
tures of dust were removed from the lungs, whereas
flint or quartzite dust remained and tended to accumu-
late on the spot upon which it had first settled down,
was not only of surpassing interest but seemed to point
to a far-reaching conclusion which might ultimately
lead to an amelioration of the lot of miners who worked
in the presence of clouds of dust of the latter kind.
It was to be hoped therefore that the experiments to
which Dr. Haldane referred would soon be resumed
and carried on until definite and, as he hoped,
eminently satisfactory results had been attained.

Value of the Practical Man.

Col. W. C. Blackett said he was not going to utter
a word against the scientific or theoretical man, but he
wanted to put in a word for the practical men who
had worked on the dust theory. After all said and
done, what had emerged from all those dust questions
both with regard to mines and in regard to physio-
logical facts which a practical man had not pointed
out? It was a practical man in the first instance
who said that colliery explosions were mostly due to
coal dust. It was a practical man who noticed in the
mine itself that where the roads were stone-dusted
explosions did not follow. It was a practical man who
pointed out how the path of an explosion had to be
pioneered by the raising of clouds of dust. It was a
practical man—Sir William Gar forth, in fact—to
whom it occurred to say that if they had found out
that stone dust mixed with coal dust in the mines
had prevented that path being followed, then surely,
it was only common sense to put stone dust there.
The experiments which subsequently followed were use-
ful, because they demonstrated, to some of those who
did not want to believe more than they could help,
that the explosion was due to coal dust, and they also
dotted the i’s and crossed the t’s of all that practical
men had pointed out before them. One practical
fact which did emerge was that the mines should be
dusted with 50 per cent, of stone dust. Sir William
Garforth had already very strongly pointed out that,
but the result of the Eskmeals experiments was to give
a suggestion as to the amount. He passed over what
Sir Henry Hall said about its not being possible or
easy to do. Some people could not think of any dust
lying in a pit except upon the floor, where it would
be covered up. Their minds seemed to be entirely
incapable of grasping that the ledges round about
held dust. He would pass over that, and go to the
question of breathing stone dust. Again it was a
practical man who said, “ Look how healthy we are
in the pits; there is less phthisis there than anywhere
else.” Then Dr. Haldane in his paper pointed out
that miners were more free from phthisis, as the
result of all that dust menace, than were agricultural
labourers—Heaven knew what they were breathing!
It was a practical man who said, “ Even if there is
dangerous dust in the pits, it does not necessarily
follow that it is going to be raised always in such a
dangerous condition as to make breathing it a menace
to life.” They had never yet confessed that the clouds
of dust which naturally occurred in pits were dan-
gerous clouds from that point of view. But then they
had to come to what he supposed Sherlock Holmes
would call “ The Episode of the Gorged Guinea-Pig,”
and in order to make a guinea-pig die, he was fairly
stuffed with dust. But that was not what a practical
man would have done; he would have said, “No, do
not take your guinea-pigs and shut them up and gorge
them with dust; take them down the pits and leave
them there a month or two and see what they are like
then, if you are going to admit that guinea-pigs’ lungs
are like men’s lungs.” The moment the scientific
man said, “Look at our guinea-pigs: see how they
have been dying! ” it was seized upon as an excuse
there and then by men who did not want to .dust their
mines. They said, “Oh, well, we had better wait,”
and that helped to delay the matter. Then flue dust
—that was another little thing to help to overcome
objections to using dust. A manager who had not got
grinding machinery, who had not suitable shale, would
raise difficulties and delay about putting the remedy
into a pit. He had plenty of flue dust of the finest
kind; it did not take very much trouble to put the
flue dust in, and there were lots of collieries using
flue dust because it was easy and they were egged on
to do it. It was said, “ Oh, but the guinea-pigs again,
you know; they die”—or they were going to die—“ of
flue dust.” He did not think they actually died; they
were only going to die. So the difficulty was raised
again, and that quite regardless of the fact that prac-
tical men said, “Why, we have had men going in
week after week sweeping up this fine dust from the
hot flues in greater clouds almost than you can gorge
your guinea-pigs with; we have men doing that week
after week, month after month, and we have never
had a thing happen to them, though they were going
into clouds of pure flue dust raised in a way in which
it will never be raised in a mine under the worst
circumstances.” Now at last they found that Dr.
Haldane was getting a little salvation, and he came
and dotted the i’s and crossed the t’s, and said, “ You
were right after all, some of you practical men,” and
he clapped them on the back, and said, “ Now you can
go your way happy, and I hope you will.”

Active and Inert Dust.

Dr. W. F. Smeeth said that in the case of the Kolar
mines of Mysore they had a dust composed partly of

quartz and partly of various crystalline silicates—
probably 40 per cent, or more of the latter—and so
far as they knew, that dust had not proved injurious
nor given rise in any marked degree to miner’s
phthisis. That case appeared to bear out the author’s
contention that the large proportion of silicate dust
present was sufficient to render the quartz dust inno-
cuous by securing its removal from the lungs. Oh
the other hand, the author referred more than once
to the injurious effects of granite dust, and appeared
to suggest that they were comparable to the effects
produced by quartz dust. Granite, however, was by
no means mostly quartz and would contain as a rule
50 per cent, or so of silicates. Dust from granite
would contain as much silicates as the dust of the
Kolar mines, so that if it could be regarded as fairly
established that granite dust was highly injurious
while Kolar dust was innocuous, it would appear that
immunity was not dependent simply or solely on the
presence of a large proportion of silicates. Similarly
they had the dust of the Cripple Creek mines, which
was stated in the paper to contain 70 per cent, to
80 per cent, silica, by which he presumed that quartz
was meant, and to be without apparent injurious effect,
whereas granite containing much less quartz and some
silicates was said to be very injurious. Those were
points which he merely mentioned because he thought
they required some further consideration. With
regard to the question of granite, the author stated
that granite dust was very injurious, but he was not
very clear whether that dust was entirely granite dust
or not. Was it from granite quarries or mines or some-
thing else in which granite and nothing else but granite
was being worked, or was it a granite combined with
quartz, in which case, of course, one could get up
to any amount of silica one liked in the form of quartz.
But if it were granite dust, then, as he had said, they
had two very different cases of dust, both containing
about 50 per cent, of silicates, the granite on the one
hand and the Kolar stuff on the other, one bad and
the other not bad. He thought that that required
further work or explanation. Other factors besides
the character of the dust might enter into the pro-
blem, especially when comparing widely separated
localities, and it would be a difficult matter to take
account of all of them. It seemed, however, as though
the experimental methods described by the author
should be capable of deciding definitely whether the
silicates contained in the granite behaved so differently
from those contained in the Kolar rocks, as suggested
by the records of the health of miners. Was it true
that the silicates of the granite were so inert that
they did not excite the dust-collecting cells to wander
out and perform a scavenging function, whereas the
silicates of the more basic rocks of Kolar gave rise
to considerable mobility of the cells sufficient to effect
the removal of the silicate dust and the quartz asso-
ciated with it? In both cases the silicates were
crystalline minerals solidified from a state of fusion,
and it would be interesting to know if the clean dust,
that was to say freed from quartz for the purpose of
experiment, of one set of silicate really gave rise to
so much more physiological action than that from
the other set. If that difference were confirmed it
would probably be related to the marked difference in
chemical composition of the two classes of silicates
involved, and further experiment might show that
the active principle was associated largely with a
particular mineral or group of minerals; for example,
it might show that felspar dust was inactive com-
pared with dust of the ferro-magnesian minerals.
There might be other ingredients also. On the other
hand, it might be found that the dust in those two
cases after experiment did not yield very different
results, in which case the marked difference in the
physiological action and pathological results, which
had been noted, would have to be sought in other causes
or local conditions. The suggestion that the activity
of certain forms of dust was due to their power of
adsorption was extremely interesting, and that power
was no doubt affected largely by chemical composition.
It would depend also on the physical constitution of
the dust particles and particles which were porous or
heterogeneous, which might be expected to give better
results than solid, homogeneous particles on account
of the increased opportunities they would offer for
surface action in proportion to their masses. The
quartz particles would be solid and free from cleavage
cracks, and that, combined with the refractory
chemical character, might well render them very
inactive. Most silicates, and particularly the basic
silicates, would be less obdurate chemically, and would
tend to possess cleavages or to occur in flattened forms
giving rise to relatively greater surfaces. The dust
from shale, even though it was largely crystalline, was
likely to be extremely minute or composed of minutely
complex particles which would be relatively porous
or permeable by solutions or gases. Coal stood in a
different category from a chemical point of view, and
its powers of adsorption, which were referred to in
the paper, might be influenced by porosity and the
presence of relatively volatile constituents. He would
like to ask the author if any experiments had been
made with charcoal dust. Charcoal dust was extremely
porous and had great power of occlusion—and
probably of adsorption—and it would be interesting
to know if, in similar circumstances, it would be more
stimulating than coal dust. In view of the suggestion
that miners and others who had to inhale dangerous
forms of dust might be made to inhale a proportion of
highly active dust, with a view to promoting a scaveng-
ing action, the search for a still more active dust than
that produced from coal might be worth consideration.
He would like also to ask the author whether the
tubercle bacilli were taken into what he had called the
dust-collecting cells, in normal cases in which there
might be no absorption of mineral dust. If so, would
a course of dusting with a highly active form of dust,
such as coal dust or perhaps charcoal, tend to promote
the removal of cells containing bacilli and so reduce
or remove the opportunity for phthisis to develop?

Mr. John Gerrard said he was very pleased that
Dr. Haldane had found what he (Mr. Gerrard) and