1264

THE COLLIERY GUARDIAm

December 29, 1916.

This last is the same as the 3 ft. 10 in. stream struck in
the borehole half a mile to the east.

Samples from these seams gave the following results
on analysis:—

Between

A challowa

Achallowa. &Amandim. Oba River.

2 ft. seam. 1 ft. 2 in. seam. 3 ft. 2 in. sm.

	Per cent.	Per cent.	Per cent.
Fixed carbon 		’ 24'73	...	37'18	..	4S'84
Volatile carbon 		28-38	...	34'52	..	35'26
Ash 		42'56	20'10	7'86
Moisture 		4'33	8'20	804
	100'00	100'00	100'00
Sulphur			0'81	1'54	3'44
Calorific value (cal.)	3,982	5,598	..	6,795
Specific gravity 		1'6-1'8	... 1'35-1'75 .	.. 1'32-1'46

Outcrop Area of the Udi-Okwoga Coal Field.

The line of outcrops in the vicinity of the eastern
escarpment extends northward from near the source of
the Mamu River, south of Udi, to Otukpa, north-west of
Okwoga, a distance of about 72 miles in a direct line.
Coal is found outcropping almost continuously between
these two localities. The westerly limit of the area runs
northward from the Mamu River through the Oji River,
via Oha Obenagu and Amandim in the Udi district,
and thence within a few miles of Ogrugru to Angba in
the Idah district.

In the Udi district, the width of the area, in an east-
to-west direction, over which outcrops have been
observed, is about 10 miles. The area widens north-
ward, until at the northerly limit, as at present known
in the Okwoga and Idah districts, its width is about
40 miles. Taking the average width from east to west
as about 25 miles, the area over which known outcrops
occur amounts to about 1,800 square miles.

Recent Developments.

The Udi Colliery is situated in the vicinity of Enugu
Ng wo where an adit has been driven in the Obweti
Valley. Work is proceeding by the bord-and-pillar
system. The roof requires careful timbering. Local
timber has been used, but this is becoming scarce,
and supplies are now being obtained from Lagos.
The timber loses its strength rapidly, partly through
dry rot, and partly through the activity of the borer
beetle.

There is a fairly plentiful supply of labour. The
local bush natives are good colliers, and are working on
the piece system. In November 1915 between 600 ^id
700 men were employed at the mines. The output of
coal up to December 31,1915, was 7,182 tons.

REORGANISING STATISTICS.

At a meeting of the Royal Statistical Society, on
Tuesday, December 19, Mr. Geoffrey Drage (vice-
president) read a paper, entitled “ The Reorganisation
of Official Statistics and a Central Statistical Office,”
on the grave deficiencies in our national statistics and
the urgent need of a central statistical office, (1) for the
much-talked-of economic reconstruction in the United
Kingdom, (2) for the closer economic union with the
oversea dominions, and (3) to solve the economic
problems which confront the Allies in consequence of
the resolutions passed at the Paris conference.

Economic reconstruction must in the long run be
founded on statistics, and Mr. Drage showed how
defective is the statistical information now available on
such vital subjects as (a) the number of trained British
seamen, (5) the trade of the United Kingdom, the
dominions, and foreign countries, (c) expenditure on
national health insurance, and housing reform.

The remedy proposed (a central statistical office) had
been recommended in vain by experts for many years
past. As long ago as 1871 Mr. Purdy read a paper before
the society suggesting a central department and enum-
erating its duties. A committee, which sat from 1877 to
1879, and included Mr. Childers, Mr. Balfour, Lord
Welby, and others, recommended a central board above
the departments to obviate official rivalries and secure
uniformity. Fresh criticisms were passed on the existing
chaos in 1907-09 by Sir Charles Dilke, president of the
society, Prof. Bowley, and others, and a central depart-
ment was again recommended. Sir Charles Dilke said
that the industry and experience of a Giffen were
necessary to detect even one-tenth of existing defects.
Mr. Drage gave a summary of these, laying stress on
the lack of co-operation between the Departments and
the absence of any central or general supervision, and
adding that to the present confusion was due, in some
measure at any rate, the distrust which official figures
inspired in those who had to deal with them. He
suggested, inter alia, that the Statistical Abstract for
the United Kingdom should be provided with intro-
ductory memoranda, maps and diagrams like the
volume of London Statistics. He proposed that the
new central authority should be above the depart-
ments and directly under the Prime Minister; in fact,
form a civil intelligence bureau which would do for civil
matters the work done in defence matters by the staff
of the Imperial Defence Committee. Such a department
would give the Prime Minister what he alone of
European Premiers lacks, namely, an adequate perma-
nent personal staff. Such a staff would assist him to
keep in touch with and control the departments which
sadly lack such supervision.

An examination of imperial statistics showed similar
evils. There is no common statistical method for the
Empire. There is not even a common statistical year.
Mr. Drage set out the divergencies existing between the
self-governing dominions and the United Kingdom in
the forms of returns and their statistical content, and
mentioned the action taken in recent years. He showed
how such an office as that contemplated would facilitate

the work of the Imperial Conference, and how the
Colonial Abstract might be improved.

Turning to our relations with foreign countries, he
touched on the work of the Institut International de
Statistique and the International Conference of 1910 at
Brussels, which was called to discuss a uniform classifi-
cation of imports and exports, and gave the model form
of classification recommended by the Conference. He
discussed possible reforms in the Foreign Abstract
at present published.

He recommended that the Premier’s office, or the new
Department of Civil Intelligence for the United King-
dom, should be expanded for the Empire under the
Premier as President of the Imperial Conference. The
Department would then consist of three sections, (1) for
the United Kingdom, (2) for the Empire, (3) foreign
and miscellaneous, each of which would publish an
annual statistical abstract.

Mr. Drage showed that, even when national statistics
had been thus centralised and reformed, there would
still be left ample statistical work, not only for munici-
palities such as that undertaken by the London County
Council, but also for learned societies, as well as for
individual expert criticism. Eternal criticism was, he
said, the price of truth.

THE STRESSES IN CAST IRON
TUBBING SEGMENTS.

When a coll’ery shaft, or some part of it, is lined with
successive rings of cast iron segments (see fig. 1) the
outside pressure from the surrounding material gives
rise to f< -rces which act on the segments in a circum-
ferential direction. In order to see how and to what
extent these forces are a cause of stresses in the material
of each segment, the following case has been worked
out. This example is purely imaginary and actual
figures have been used instead of symbols.

The finished inside diameter is assumed to be 18 ft.;
the length of each segment on the s raight, between the
centres of its ends, is 3 ft 9 in. ; and there are . 15
segments, each having a radial width of 4§ in. and a
vertical height of 21 in.

\

\

\

\

\

\

\

\

Fig. 1.—Section of a Lined Shaft.

0-10

0088.

'0529

-910

-FOR P'U

148
___________DEPTH OF 5ECTI0N-

Uj ....-------------

I
g

g 0302 xforP>

ZERO

STRESS

'uJ

CO
z

Fig. 2.—Plan, Elevation and Section
op a Segment.

Fig. 2 shows a plan, elevation and cross-section of a
segment, the fillet used for purposes of connection
being left out. The segment considered in the present
case is the one shown at the top of the plan (fig. 1),
and is supposed to be under the worst conditions by
having little or no external support from the ground,
thus being reduced to the case of a short pillar loaded
eccentrically.

The forces will act in directions parallel to the
tangents at the joints. Call these tangential forces W.
Then the endwise forces on a segment will be P = W
cos 6, where 0 is the angle between the tangent and
chord.

Three cases are taken, two of these being extreme,
and the actual points of application of the forces being
dependent on the manner of forming the joint. Let
these three cases of loading be represented by P', P", P'".
Of these loads, P' is supposed to pass through lines
on the ends of the segment which are near the outer
edge; P" passes through lines half-way between the
outside and the inside, and P'" through lines which are

near the inside edge. Referring now to the section on
fig. 2, the following calculation gives the distance of
the neutral axis from the inner edge of the section, B C,
y =	*21x31) =

where the area

A' = 21 x 4— 15J x 2J = 512 sq in.

The moment of inertia about the neutral axis N A,

I _ pj5_x_(|;5)» + 5.25 x 4.5 x (0.74)2J

+ p-75 X^IW + 15 75 x 1 75 x (0.635)* | = 71m.
From fig. 2 the distance of tbe load lines of P', P", and
P'" from tbe neutral axis are

a' = |

a" - H

a" - 31

In the cases of any of the three loadings P', P", P'"
the stress at E F due to the bending action is

where y’ = 2'99 in.

iz*	a' y” P

= —— where y' — 1'51 in.

6	1

From these the bending stresses at tbe top and bottom
edges respectively are calculated as for positions P'.

J' =	=	= 0-010.5 P'..(+)

and

j' =	= I x _x..p/ - 0 0053P'...........(_)

Similarly, f" _ 0.0526

Jb

f" = 00266 P".......( + )

J b

and	f'" = 0'1345 P'"....(-)

Jb

C" = 00690 P"......(q-)

Jb

All stresses are in tons per sq. in. where the
loads are tons. The (-{-) sign denotes a compressive
and (—) sign a tensile stress.

The uniform compressive stress I which is always
Jc

acting as well as is

Jb

f == 512 = 9’9196 P ............(+)

Jc

The stresses may now be added to find the effective
stress.

ForP'atEF ( = f -f- f' = 00302P' ...........(f)

Je	Jc	Jb

at BO [ = f - f = 00144P' ............(+)

J e	J c	J b

ForP"atEF f = P- f = 0 0329 P" .............(—)

Je	J b Jc

at B C f = I + f"= 0 0463 P" .........(+)

J e	J c	, b

ForP'"atEF f = f -01148P'"..................(-)

Je	Jb	Jc

at BO f = f +	= O-OO87P"'.......(4-)

Je	Jc	Jb

The largest compressive stress is attained with P'"
when i at B C is 0 0463 P", or putting [* =35 tons

J e	J e

per sq. in.

Now take J = 10 tons per sq. in.,

P" = q7q^29 = 394 tons where I is assumed to be 10,

and P"' =	= ^7'5 tons with same value for

J e.

All this means that, assuming the ultimate compres-
sive strength of the material to be 35 tons per sq. in.,
and the ultimate tensile strength to be 10 tons per
sq. in. for tension caused by bending, the values
for tbe loads likely to cause fracture can be calculated.
The figure of 35 for the compressive strength of cast
iron is, perhaps, somewhat low, but unless something
very definite is known about the material in question, it
is not safe to assume it to be higher. The tensile
strength, in bending, of 80 tons per sq. in. may
also be considered to be on the low side, but it has been
found that in tests of heavy castings of this nature the
calculated tensile stress at fracture may be as low as
8 tons per sq. in. As a rule, it is found that in
cases like P'", where the tensile stress predominates, the
calculated value for this is relatively low and the

» e

actual fracture is complete and instantaneous. On the