March 7, 1913

THE COLLIERY GUARDIAN.

487

again to its former position and is ready to start the
pump afresh should occasion arise. In connection with
the sprinkler installation there is provided a simple and
efficient fire alarm, which immediately gives warning in
case of even a small escape of water inside the building,
whether the cause of the escape be a leaky joint, a faulty
pipe, or the operation of a sprinkler. The alarm con-
tinues to be sounded as long as the escape takes place.
This device is operated by a valve connected with a
small water wheel having revolving hammers which
beat against a gong.

THE BOARD OF EDUCATION EXAMINATIONS
IN COALMINING.

The Board of Education has just issued in a Buff
volume a collection of the Lower and Higher Examina-
tion Papers set at the General Examination in Science
and Technology held during the year 1912, these being
the first examinations held under the reorganised
system introduced' in 1911. The volume also contains
the reports of the examining committees upon these
examinations. In a prefatory note it is observed
that the general standard of the work done at the
examinations has doubtless been affected to some extent
by the decrease in the proportion of candidates coming
from the larger technical schools, while teachers
are exercising more freely the opportunity now given
them by the regulations to adapt their syllabuses to
local requirements and to provide their own tests of the
work done by their students.

The examining committee in the coalmining and
metallurgy group consisted of Professors Henry Louis,
D.Sc. (chairman) and J. O. Arnold, D.Met., F.R.S.,
Mr. T. T. Rankin, C.E., B.Sc., M.Inst.M.M., M.I.M.E.,
principal of the Wigan Technical and Mining School,
and Mr. G. H. Winstanley, M.Sc., Tech. H.M. Inspector
of Schools. The papers set to candidates in coalmining
are given below. The examination, it may be added,
lasted three hours, only one of the two papers to be
attempted. The value attached to each question is
shown in brackets after the question. In the Lower
Examination only eight questions were to be answered,
and in the Higher not more than six, including Nos. 23
and 26.

Lower Examination.

1.	Explain what you understand by normal and reversed
faults, and show how they affect a seam of coal traversed
by them. (25)

2.	State exactly what you mean by the strike and dip of
a coalseam, and how you would determine in the mine their
directions and the amount of the latter. (25)

3.	Describe a form of diamond drill suitable for proving
a coalseam, supposed to exist at a depth of about
1,000 ft. (25)

4.	Describe a percussive coal-cutter, suitable for kirving
or holing in a thin seam of hard coal. (25)

5.	Describe in detail how you would put in a wedging
crib and foundation ring for tubbing in fairly strong ground
at a depth of 500 ft. below the surface. (25)

6.	Give a full account of the Welsh system of stall-
working. (25)

7.	Describe the lay-out of a self-acting incline, and show
what conditions must be fulfilled in order that any given
incline can be thus arranged. (25)

8.	Make a drawing of a two-decked cage, capable of taking
eight ordinary tubs; indicate the principal dimensions. (25)

9.	Describe any form of underground electric pump,
capable of raising 1,000 gallons per minute against a head
of 1,000 ft. (25)

10.	Describe any form of regulator, and explain fully
where regulators are placed in a ventilating system, and
with what object. (25)

Higher Examination.

21.	Give a brief description of any one of the following
coalfields:—South Wales, Lancashire, Northumberland and
Durham. (55)

22.	How would you ascertain whether, to what extent,
and in which direction a deep borehole had deviated from
the perpendicular ? (55)

23.	It is proposed to work a thin seam of coal, dipping
2 in. to the yard, by longwall, using coal-cutters and faca-
conveyors; the roof and the floor are good. Show by
drawings how you would lay out a district for the above
mode of working, and describe the machines you would
employ. (65)

24.	Compare the advantages and drawbacks of main-and-
tail and endless-rope haulage. (55)

25.	Describe in detail the process of sinking a shaft
through weak, wet ground by the use of underhanging
tubbing. (55)

26.	A mine is ventilated by a furnace, which produces a

current of 200,000 cubic feet of air per minute with a 2| in.
water-gauge; you are required to replace the furnace by a
fan to produce a current of 300,000 cubic feet per minute.
Show how you would arrange the work, and draw up a
specification of the fan and fan-engine that you would
employ. (65)	I

27.	State the principle of the safety lamp, explain how it
may be used for the detection of firedamp in the pit, and
describe in detail any one form of lamp suitable for this
purpose. (55)

28.	Describe the construction and mode of action of a
multiple-stage centrifugal pump, direct-coupled to an electric
motor, suitable for pumping 1,000 gallons per minute
against a head of 1,000 ft. (55)

The report of the examiners is not enthusiastic. In
regard to the Lower Examination they state that,
generally speaking, the exercises, taken as a whole, were
very disappointing, and they impress upon teachers that
this examination is of a decidedly higher standard
than the old Stage 1, and that it is intended for
candidates who, after a suitable preliminary course,
have studied the subject of coalmining for two
or three years in evening classes. The sketches, as
a whole, were poor, and evidently sufficient time is not
devoted to practice in hand sketching. Many students
are obviously “deficient in lack (sic) of descriptive
power and should be given considerable practice in the
art of expressing themselves intelligently, and be shown
that a knowledge of the subject, without power to put
such knowledge on paper, is imperfect training for an
examination like this.”

No doubt, say the examiners, the low standard attained
is to some extent due to the fact that teachers have
attempted to work through the whole syllabus in the
course of one year, and this difficulty would be to a great
extent met by extending the course of teaching in
mining over two or three years.

Dealing with the individual questions, the examiners
remark that many students attempted to cover their
ignorance by describing something not asked for; this
occurred frequently in the answers to Questions 4 and 6.
In their observations on Question 7, the examiners say
“ very few of the candidates appeared to have the least
idea of the mechanical or arithmetical principles
involved in making the requisite calculations,” a lack of
arithmetical teaching which was also very strongly
marked in the answers to Question 9. In regard to
Question 10, they say “it is rather a serious reflection that
so few candidates appeared to appreciate the object of a
regulator, as this is a matter of considerable importance
from the point of view of the practical worker.”

In reference to the Higher Examination, the
general conclusion of the examiners is as follows:—
“ It is evident that the wide range of this subject is one
of the serious difficulties for both teachers and students,
and it may be suggested that two years should be given
to the study of the subject-matter of this higher stage,
and that candidates should not attempt the Higher
Examination until two years after the Lower Examina-
tion has been passed, some local test being, if thought
desirable, applied at the end of the first of these two
years of study.”

An observation arising from the answers to Question
21 is that “ it would seem that the subject of the general
structure of the British coalfields is not as widely, or
as well taught as it should be.” As to Question 22, the
examiners believe that no single candidate who attempted
it had even seen the operation put into practice,
suggesting that this part of the subject is carefully
crammed, possibly to the detriment of more practically
important sections ; “ teachers do not sufficiently study
the balance of the subject of coalmining as a whole, paying
perhaps undue attention to those portions which come
earlier in the syllabus and slurring over those which
come nearer to the end.” Question 25 was extremely
badly answered, no less than 155 answers out of 220
receiving no marks at all, owing to the candidates
describing other methods of shaft sinking than that
called for; “ many teachers evidently do not take care to
keep their advanced work sufficiently up to date.” The
answers to Question 26 were very poor, and showed in
many cases that the elementary principles of ventilation
were not understood. Question 28 was attempted by
very few, and rarely with much success.

Rescue Work in the United States.—The executive com-
mittee of the American Mine Safety Association have sent
out letters to those eligible for membership, all over the
country, setting forth the plan and scope of the association
and outlining the permanent organisation. The association
will fix the standards of practice in mine safety, in mine
rescue methods and in rendering first aid to the injured.
It is also to set the standards for construction and use of
devices and appliances for mine rescue and first aid work.
The annual meeting of the association is to be held in
September, and will probably come to Pittsburg. Mr.
H. M. Wilson, engineer in charge of the Arsenal station of
the Bureau of Mines, is chairman of the executive com-
mittee. The association is to be a combination of private
and Government enterprise, and will, of course, have the
sanction.of the Bureau of Mines.

EXPLOSION-PROOF MOTORS.

At the United States Bureau of Mines an investiga-
tion of explosion-proof motors has just been completed,
and the results are contained in a report by H. H. Clark
(Bulletin 46). The term “ explosion-proof ” is here
used to refer to motors so constructed that an explosion
I within the casing will not ignite external explosive
mixtures, and the tests were carried out on five motors
supplied by manufacturers in response to a circular
from the Bureau.

Without entering into a detailed description of the
test conditions, it may incidentally be of interest to
refer to a gas percentage indicator which was specially
devised in order to obtain accurate mixtures by com-
bining proportionate volumes of gas and air. In this
instrument, which is shown in the accompanying figure
(fig. 1), a small quantity of the gaseous mixture is
burned in close proximity to a thermo-couple connected
to a delicate millivoltmeter. The device was connected

Fig. 1.—Details of Gas-percentage Indicator.

a, point at which gas is burned—b, spark-point—c,
water-gauge connection—d, vent for burned gas—
e, control valve—thermo-couple—g, gas intake—
h, water-jacket discharge—i, water-jacket inlet—
fc, uptake tube—I, ignition wire—m, millivoltmeter
n,thermo-couple terminal—o, double layer of gauze.

O

e

a
f'
b
a-

■FREE AIR
INTAKE

MOTOR UNDER
TEST

Fig. 2.—Plan of Testing Apparatus.

a, gas-percentage indicator—b, millivoltmeter—c,
6 in. quick-closing gate valves—d, gas-meter—e, gas-
control valves—/, air-controlled valve—g, recording
pressure-indicator—h, release magnet for pressure
indicator—i, 1| in. quick-closing gate valves—k,
spark plug for igniting mixture within casing.

to the fan discharge so as to indicate the percentage of
gas in the mixture that was being circulated through
the gallery. By setting the valves in the piping system
so that the fan took the mixture from the motor casing
only, it was possible to determine immediately and
accurately when the casing had become filled with the
correct mixture. A plan of the testing apparatus is
shown in fig. 2.

The protective devices tested have been classified
under various types. Thus Type A consisted of three
layers of gauze protected by a poppet value (fig. 3).
Type B consisted of two unprotected layers of gauze
having an exposed area of approximately 4 by 5J inches.
Type 0 consisted of five brass baffle plates, Type D
of two sets of plates, one of which was located at each
end of the motor casing (fig. 4), and Type E of two sets
of gauze and baffle plates, one of which was placed at
each side of the motor casing at the commutator end
(figs. 5 and 6).

In the case of Type A devices 191 tests in all were
made under 45 different conditions, each condition
being tested at least twice. Flames were discharged