June 12, 1914.

THE COLLIERY GUARDIAN.

1301

on-Tyne in 1887. In 1888, Mr. Strzelecki was appointed
chief assistant to the honorary secretaries of the New-
castle-on-Tyne meeting of the British Association for the
Advancement of Science. After assisting the late Mr.
John Daglish, mining engineer, of Marsen Hall, South
Shields, for a few months, Mr. Strzelecki entered the
service of the Institution of Mining Engineers in 1891,
being the first permanent official engaged by the institution
after the appointment of the late Mr. M. Walton Brown as
secretary in the April of the same year. The affairs of
the institution were at that time in a very involved and
unorganised condition, so that much important work fell
to Mr. Strzelecki’s share. In 1898, he was appointed
cashier in addition to being chief assistant, and up to
the time of Mr. Brown’s death in 1907, relieved Mr.
Brown of all the routine work of the institution. Mr.
Strzelecki also assisted Mr. Brown in that gentleman’s
capacity as secretary of the North of England Institute
of Mining and Mechanical Engineers, secretary of the
Joint Committee of the Northumberland and Durham
Coal Owners’ Associations, secretary of the Board of
Examinations for the Mining district of Newcastle, etc.
On the death of Mr. Walton Brown on November 22,
1907, Mr. Strzelecki was appointed secretary pro tem.,
and editor of the Transactions, and continued in that
capacity until September 1, 1908, when he was appointed
assistant secretary, with charge of the office, which it
was then decided should be removed from Newcastle to
London, with Prof. L. T. O’Shea, of Sheffield University,
as hon. secretary.

It will be seen from the above brief sketch that Mr.
'Strzelecki has during the past 28 years been constantly
■engaged in work of an administrative character, 23 of
which has been devoted to the interests of the Institution
of Mining Engineers. The decision of the council that
Mr. Strzelecki shall in future be designated secretary
instead of assistant secretary is evidence of the high
appreciation in which he is held by them, and is a fitting
recognition of the services rendered to the institution by
that gentleman during so many years.

We might mention, in conclusion, that prior to the
death of Mr. Walton Brown in 1907, Mr. Strzelecki was
for many years a frequent contributor to the columns of
this journal.

OBITUARY.

We regret to record the death of Mr. J. Coulthard Walton,
of Huish House, .near Radstock, which took place with
painful suddenness at Wallsend-on-Tyne on Saturday, May
30, the cause of death being heart seizure. The deceased
was 56 years of age, and was about to start on a holiday.
Mr. Walton was born at Alston, in Cumberland, in 1858. He
served his apprenticeship as a mining engineer at the
Heworth Colliery, near Newcastle, under Mr. John Simpson.
On obtaining his first-class certificate he was appointed
manager to the Benwell Colliery Company, under Mr.
Cochran Carr. In March 1883 he was appointed manager
of the Writhlington and Kilmersdon Collieries, at the time
when the late Mr. John Batey was agent. On the death of
Mr. Batey the deceased was appointed agent, and held the
dual positions up to the time of his death. Throughout his
31 years’ connection with the Somerset coalfield, Mr. Walton
has been held in the highest esteem and respect by all classes.
The funeral took place on the 3rd inst. He wTas a member
of the Somerset Coal Trade Conciliation Board, chairman of
the managers’ section of the Coal Owners’ Association,
chairman of the Coal Mines Rescue and Aid Committee, a
member of the Somerset County Council Mining Instruction
Committee, the representative for the parish of Kilmersdon
on the Erome Board of Guardians and Rural District
Council, and parish warden for Writhlington.

The death took place on Monday of Mr. Edward Bindon
Marten, of Stourbridge, who was well known as an engi-
neer, having carried out many important works in the Mid-
lands. In 1865 Mr. Marten systematically investigated the
subject of the drainage of mines in South Staffordshire, and
in 1871 he became the engineer to the Commissioners under
the South Staffordshire Mines Drainage and Improvement
Act of 1873. On resigning that position in 1908 he was
appointed consulting engineer. This position he held only
for a short time, and in the following year resigned owing
to failing health. He became a member of the Institution
of Mechanical Engineers in 1859, was a member of the
council from 1886 to 1891, and was vice-president in 1892.
He was also a member of the Institution of Civil Engineers.

North of England Institute of Mining and Mechanical
Engineers.—A general meeting will be held in the Wood
Memorial Hall, Newcastle-upon-Tyne, at two o’clock
to-morrow (Saturday). The following papers will be open
for discussion :—‘ ‘ Stone Dusting at Bentley Colliery : Report
to the Doncaster Coal Owners’ (Gob Eires) Committee,” by
Mr. Robert Clive; “The Automatic Distribution of Stone
Dust by the Air Current,” by Mr. H. W. G. Halbaum;
“ Notes on Gob Eires and Blackdamp, etc.,” by Mr. John
Morris. The following paper will be read or taken as read :
“ The Killingworth Colliery (New South Wales) Explosion,”
by Mr. James Ashworth. A mine signalling apparatus and
mechanical bells will be exhibited, described, and demon-
strated by Messrs. E. C. Theedam Limited. The council
have arranged an excursion meeting to the Home Office
Experimental Station at Eskmeals, to take place upon
Saturday, June 27, provided a sufficient number of members
signify their intention of taking part as will justify the
expense. The North-Eastern Railway Company will run
a special train, leaving Newcastle-upon-Tyne Central Rail-
way Station about 9 a.m., arriving at Eskmeals Railway
Station about 12.30. The return train will leave Eskmeals
Railway Station about 5 p.m., arriving at Newcastle-upon-
Tyne Central Railway Station about 8.30 p.m. The follow-
ing, amongst other experiments, will be carried out :—(1)
An attempt to ignite a one to one mixture of coal and incom-
bustible dust; (2) a coal dust explosion; (3) a demonstration
of the safety lamp tests; and (4) experiments regarding the
initiation and propagation of firedamp explosions.

On the Electrification Produced during the Raising of a Cloud
of Dust.

By W. A. DOUGLAS RUDGE, M.A.

Abstracted from the Proceedings of the Royal Society.

In a paper published in the Philosophical Magazine
of May 1913 an account is given of some experiments
which show that the raising of a cloud of dust is accom-
panied by the production of a large amount of elec-
tricity. The dust was usually blown away from the
surface of a flat piece of material or from the end of a
tube. Large quantities of electricity were produced by
this means, and the sign of the charge seemed to
depend upon the nature of the material used to form the
dust cloud. Basic bodies generally acquired a negative
charge, and acidic bodies a positive charge. It might
be suggested that the origin of the charges lay in the
friction of the particles of material against the surface
from which they were blown, but this, however, is not
altogether the case, as the following experiment will
show.

An insulated brass tube, 25 cm. in length and 1'5 cm.
in diameter, was connected to an electroscope. Tubes
of different materials and of a slightly smaller diameter
were provided to fit inside it, so that the nature of the
surface from which the dust was blown could be varied.
Under these circumstances it might be expected that
the charge carried away by the dust, and also that
retained by the tube, would vary with the nature of the
surface, but this was not the case, for with the same
substance for creating the dust, the electrification was
always the same, no matter what was the nature of the
surface from which it was blown. Again, the nature of
the surface against which the dust was projected was
also without influence upon the charge acquired. It
has been shown that the charge upon the dust is appa-
rently accompanied by one of opposite sign upon the air.
The dust raised by blowing air is projected against the
wire gauze screen, and the greater portion is caught,
but the air accompanying the dust is carried on. At
some distance (50-100 cm.) behind the gauze a small
radium-coated plate served to collect any charge present
upon the air. Electroscopes indicate the charges
acquired. The electrification first indicated is not due
to the friction of the dust against the wire gauze, for a
charge of the same kind is shown by spraying the dust
directly into the air.

Up to this point the work had been carried on at the
University College, Bloemfontein, and in the open air,
but since then the experiments as detailed in the
original paper have been repeated under different
climatic conditions, and also within a room in the
Cavendish Laboratory. The result has been to confirm
the previous experiments, and although some variations
do occur, the general laws appear to be well substan-
tiated. In the earlier experiments there was a more or
less free motion of air and dust permitted, but it was
thought advisable to conduct the experiment in a con-
fined space. A number of experiments were made,
which showed practically the same results as those
obtained by spraying in the open air.

This arrangement was very sensitive as a means of
detecting the charge upon the air, and some attempts
were made to get quantitative results, that is, to find
some relation between the charge of electricity upon the
air and the quantity of material sprayed. Mercury
sulphide was the substance used-, as this was found to
be the most efficient dust for producing electrification,
but the efficiency depended upon the fineness of the
powder. It was found that one puff was sufficient to
charge the radium collector up to a potential of from six
to eight volts. Molybdic acid was also very efficient.
This small amount of dust, 5 xlO-9 grammes per cubic
centimetre, gave a charge which raises the potential of
the exploring electrode to several volts, so that the
actual amount of dust which would produce a detect-
able charge might well be 1/1000 of this amount.

Blowing a few centigrammes of cornflour into a large
room* charged the air to such an extent that a radium-
coated collector rapidly indicated a potential of 200
volts, and the charge persisted for some time.

On several occasions it had been noted that a reversed
charge was given to the wire gauze used to collect the
dust, and this appeared to be due to the rate at which
the cloud of dust was raised, as well as to the influence
of the opposite charge upon the air. The box used for
the last series of experiments was employed to carry out
another series in which the .dust was ‘ ‘ rained ’ ’ into the
box instead of being sprayed. In this case the curious
result was obtained of a negative charge being nearly
always given up to the insulated vessel, and the air as
tested by a radium-coated conductor was also negative.
Only very small amounts of material passed through the
close meshes of the sieve; a milligramme or so of most
substances would raise the potential of the insulated
conductor to three or four volts. Varying the distance
of fall from 10 to 30 centimetres had no influence on
the nature of the charge, but merely dropping the
powder in a mass produced no charge, it being neces-
sary apparently for the particles to be spread apart or
rubbed together if a charge was to be obtained.

The experiments described so far had been carried out
with air, and it seemed of interest to repeat them with
the gases which can be obtained in cylinders, the pres-
sure under which these gases escape furnishing a con-
venient method of raising the dust. The gases avail-
able were oxygen, hydrogen, carbonic acid, sulphur

* The room had a volume of about 250 cubic metres.

dioxide, nitrogen, and ammonia. Generally the same
charges as with air were obtained.

A considerable amount of time was expended in
endeavouring to measure the current which could be
sent through air when dust was present, but the results
were very unsatisfactory on account of the large charges
initially present upon the dust. If ions are present,
they most probably are of a large size, and hence would
have a small velocity in a field of moderate strength,
and under any circumstances a certain number of
charged dust particles would reach conductors con-
nected to the electrometer, but the current through the
dust-laden air was very small. The general trend of
the experiments seems to indicate that the air does
become slightly ionised, but not to an extent comparable
with that produced by a trace of a radium preparation.

Up to the present no satisfactory explanation as to the
origin of the charges had presented itself, save the one
that these charges might be due in some way to the
enormous increase of surface of contact between the
air, and the dust which must occur when a small amount
of powder is blown into a dust cloud, somewhat in the
same manner as a strong charge is produced by break-
ing up a liquid into a fine spray as shown by Lenard
and others, and some experiments were made to test
whether this was the case. When a tube was packed
with powder and the ends closed with plugs of cotton
wool no charge was carried away by the air driven
through the apparatus unless some powder managed to
escape through the plugs. If the charge had been due
to an effect of contact of air and dust some charge
should have been obtained by this method. It must
therefore be concluded that the charges are not due to
mere increase of surface of contact between the air and
the dust.

It seems quite clear that the electrification must be
due to some mutual action amongst the dust particles,
such as repeated contact or the rubbing of one particle
upon another. Small charges only would be produced
upon the individual particles, but, as there are so many,
the collective effect might well be great. It is, of
course, well known that, by rubbing together two pieces
of the same material, two charges of electricity can be
obtained, it being presumed that there exists natur-
ally some slight difference between the two surfaces
which are being rubbed, and no doubt many observa-
tions have been made upon the matter, but the cases
recorded are few.

Some experiments were made to ascertain to what
extent naturally occurring ordinary bodies gave rise to
measurable charges of electricity when rubbed together;
it appears ■ that practically every material is found to
become charged when rubbed on another piece of the
same material, the two pieces becoming oppositely
charged.* The charges produced are comparatively
large, so that no difficulty is experienced in detecting
them with an ordinary electroscope, and very small
pieces of material suffice to give measurable charges.
The sign of the charge upon each piece of material is
apparently fortuitous, for, given two pieces, A and B,
of the same material, then A may be positive at one
time and B at another; probably there is some slight
surface difference, which is not permanent. Amongst
the substances examined, and which readily gave the
two charges when two pieces are rubbed together, are
quartz, cinnabar, Iceland spar, arragonite, tourmaline,
barytes, felspar, mica, fluor spar, sulphur, potassium
nitrate, potassium bichromate, and oxalic acid. This
list is representative, but not exhaustive, and in each
case opposite charges are obtained from two pieces of
the same substance. Of course, rubbing two pieces of
dissimilar substance also gives rise to two charges.

It is very surprising what small amounts of material
will acquire measurable charges. Pieces of cinnabar
not more than 0' 1 sq. cm. in area give very definite
charges.

In addition to the charges upon the materials, some
charge is also given to the air surrounding the material,
and the sign of this charge depends upon the nature of
the material. Thus, by rubbing two rhombs of calcite
together inside a box in which was present an insulated
wire coated with radium and connected to an electro-
meter, the latter indicated that a positive charge had
been gained by the wire, but if two crystals of quartz
were used, then the charge was found to be negative.
This agrees with the signs of the charges given to air
during the raising of a dust cloud of these materials.
These charges upon the air were not very strong, but
quite definite, especially in the case .of calcite, when the
sign was always positive. It is most probable that
small particles are abraded during the rubbing, and
these may give a charge to the air, and it is possible
that in all cases the charge upon the air is really due to
very fine particles which do not readily settle, or which
move with such velocity that they escape capture by
the charged electrodes used in certain of the experi-
ments.

The facts as revealed by the experiments are very
difficult to interpret. At present it seems quite definite
that the charges originate in the powder itself; that is,
there must be friction or contact between the various
particles, which differ in size or surface condition in

*Hesehus, Journ. de la Soc. Busse Phys.-Chim., 1901,
states that when pieces of similar material are rubbed
together they become charged with the same kind of elec-
tricity, and the dust abraded has a charge of opposite sign.