August 14, 1314.

THE COLLIERY GUARDIAN.



as the influence of the temperature, the conditions in
air being expressed by : n' —n'Q a t — b' with a' =
0-0036 and b' =0-27. It was in this way that the
values of n'o were calculated for the curves illustrated
above.

In practice the knowledge of a single curve enables
one to solve all the problems relating to the inflamma-
bility of firedamp mixtures, such as : analysis of these
mixtures by the method of the upper and lower limits
of inflammability; danger arising in pit fires by an influx
of air or outburst of firedamp; inflammability of mix-
tures heavier than air and resulting from certain
instantaneous outbursts, etc.

BOOK NOTICES.

Modern Practice in Mining. Vol. III. : “ Methods of Work-
ing Coal.” By R. A. S. Redmayne, K.C.B. London :

Longmans, Green and Company. Price, 6s. 6d. net.

Vols. I. II. and IV. of this work dealing with “ Coal
and Its Occurrence, Value and Methods of Boring,”
“ The Sinking of Shafts,” and “ The Ventilation of
Mines,” respectively, have already been issued, and
Vol. V., “ The Mechanical Engineering of Collieries,”
is in preparation.

Chapter I. of the present volume deals mainly with
the shaft pillar and the pit bottom. The size of shaft
pillars as affected by depth, nature of coal, inclination
and the effect of faults is well treated, and, though
from the nature of the case no very definite conclusions
are arrived at, good general guidance is given. The
most modern methods of support for shaft bottoms,
including reinforced concrete, are dealt with, and costs
are given for underground stables. Several examples
of pit bottom arrangements are given, but no very
modern arrangements for endless rope haulage and
large outputs seem to be included.

Chapter II. refers to main roads and their support.
A specially useful section deals with methods recently
introduced, in which reinforced concrete is utilised;
costs are given, and methods adopted in dealing with
heavy ground are well described. An error appears to
have crept in on p. 72, where W should be the total
breaking load, and not the stress per sq. in. as stated.

Chapters III. and IV. cover bord and pillar
methods of working, and Chapters V. and VI. with
longwall and its modifications. These chapters consist
mainly of the description of well chosen examples . of
the various modifications of the two systems, which
seems to be the best way of treating a rather difficult
subject. Perhaps a little more stress might have been
laid on the essential differences between the two main
systems of working coal and the factors which gener-
ally determine the success of one system or the other.

Chapter VII. deals with the support of the roof at the
working face, and consists mainly of extracts from the
reports of the Prussian Commission and the Committee
of the British Royal Commission on Mines on this
subject, and the provisions of the Act of 1911 are given
in long footnotes.

A good index adds to the value of the work. The
mechanics of roof movements are hardly touched upon,
and one cannot help feeling that this subject is capable
of some elementary treatment which would assist the
student in understanding the effects, both underground
and at the surface, of different systems of working pack-
ing and the setting and withdrawal of timber. A good
theoretical basis would help to co-ordinate and make
intelligible the varying experience which has been
accumulated on this subject under different practical
conditions.

The descriptions of the various methods of working
given in the book are clear and intelligible, and mining
students and others are greatly indebted to Sir Richard
Redmayne in that he has found time in an exceedingly
busy life to give them the benefit of his great knowledge
and experience in the work which he has published.

The illustrations and general arrangement of the work
leave nothing to be desired.

Wiring Calculations for Electric Light and Power Installa-
tions. By G. W. Lummis Paterson. London : Scott,
Greenwood and Son. Price, 5s.

This book of 96 pp. has been prepared for those who
are engaged in electrical installation work, and is there-
fore a work which appeals to mining engineers and elec-
tricians. The design of electric circuits in mines and
collieries is second in importance to no other
branch of colliery equipment, and when one remembers
that the interest upon the cables and the erection
thereof, together with the annual cost of the energy
wasted therein, is the price that has to be paid for the
transmission of energy electrically, it is apparent that
the subject matter of the book before us is of great
moment to all concerned with colliery management. At
the same time, it appears to us that books dealing with
“wiring calculations” do not, from the educational point
of view at least, go far enough. Taking as a reasonable
starting point the postulate that every problem in elec-
trical distribution must be considered according to. its
own merits, it is only right to expect that the electrical
engineer in charge of an electrical system at a colliery
should be able to design the distribution circuits accord-
ing to first principles. There is, however, a sphere of
usefulness in connection with books on wiring calcula-
tions, inasmuch as there is a demand for them. And
we wish to make it clear that these general remarks are
not intended to apply to the work under consideration.

Paterson’s “ AViring Calculations is essentially a
practical book, and has been prepared, for practical men.
The method of treatment, so far as it goes, is satisfac-
tory, and consists in explaining in a simple manner,
but somewhat briefly, the general principles of con-
tinuous and alternating currents, and the ordinary
systems of distribution. Formulae are then given in

connection with the calculations of conductors and asso-
ciated problems both for continuous and alternating
currents, and it would have been a valuable addition
if the methods of deducing these formulae had been
included. A very useful feature of the book is the
data connected with the working of continuous cur-
rent dynamos and motors, and also with alternating
current motors, and the large number of worked-out
examples included enhances the value of the book con-
siderably. Mention must also be made of the thirty-five
well arranged tables, which form the most impor-
tant part of the book, and have been prepared to
obviate waste of time in making calculations connected
with the determination of the various factors of elec-
trical distribution. The book appears to be free from
errors, but attention is drawn to a simple misprint in
line 15, p. 22, where a plus ( + ) sign is given instead of
the multiplication (x) sign. The book is cordially
recommended to those who require assistance in wiring
calculations.

Kurzer Leitfaden der Bergbaukunde. By F. Heise and F.

Herbst. Berlin : Julius Springer, 1914. Price, 6 inks.

The authors say that they approached the task of
writing this short guide to mining with some misgiving.
The result, however, shows that they have successfully
avoided the difficulties involved in dealing with so wide
a subject as mining in the compass of an introductory
text book. The subject is treated throughout in logical
sequence, beginning with preliminary geological consi-
derations, and the description of modes of occurrence of
mineral deposits in general. We do not propose here to
refer to more than that portion which particularly
concerns coal mining, although much of the information
applies both to coal and ore mining. Thus, the first
part of the second section treats of boring, and is
follow’ed closely by a chapter on blasting explosives and
the position of boreholes. Then we have shaft sinking
and methods of working, in which coal mining assumes
a prominent position. Mine gases and coal dust receive
special treatment, and these sections lead naturally to
the consideration of ventilation, which is thoroughly
well treated in considerable detail. A few pages are
then given to miners’ safety lamps. The next portion
of the book treats of mining methods in detail, and
discusses methods of support by timbering, walling and
concrete construction. Various methods of sinking in
difficult ground are described, and the most modern
methods are illustrated, including both the freezing end
the cementing process. The next section deals with haul-
age, pumping, and finally, we have a description of pit
fires and rescue apparatus. There is a vast amount of
concentration in this little book, and there are practically
no references to a wider range of reading. Mining
students who read German should certainly get it.

Coal, Mining. By T. C. Cantrill. Cambridge University .

Press, 1914. Price, Is. net.

This is another excellent addition to the Cambridge
Manuals of Science and Literature. Its object is rather
to instruct the general reader than to expound the theory
and practice of coal mining. For this purpose it is
essential that the reader should first be interested in the
subject, and Mr. Cantrill, therefore, wisely devotes
considerable space to an historical review of the subject
many of the particulars for which are reaped from
Mr. R. L. Galloway’s “Annals of Coal Mining.”
Chapters are devoted to the geology of coal and the
structure of British coalfields, prospecting and boring
and winning the coal. The technical portion of coal
mining is discussed in an interesting and not too
abstruse a style, and finally there is a brief account of
leases,, royalties, wages, accidents and State Regula-
tions. This part of the book will need some revision in
a future edition, for the text makes no reference to the
Coal Mines Act, 1911, and some of the statements
referred to are no longer quite correct. We can cordially
endorse the author’s views respecting the neglect of
borehole information by the State, as well as the
inaccuracy of many of the older mine plans.

Petrology of the Sedimentary Rocks. By F. H. Hatch and

R. H. Rastall. London : George Allen, 1914. Price,
7s. 6d. net.

Text Book of Petrology. Vol. 1 : The Igneous Rocks. By
F. H. Hatch. Seventh Edition Revised. London :
George Allen, 1914. Price, 7s. 6d. net.

A great service has been done for students of rocks
by the publication of a new volume on “ The Petrology
of Sedimentary Rocks,” as well as a new edition of
Dr. Hatch’s well known work on “ The Petrology of
Igneous Rocks.” These two books now form a set
covering the petrology of the whole series of rocks
entering into the composition of the earth’s crust. The
petrology of the sedimentary and metamorphic rocks has
not before been treated on so detailed and comprehen-
sive a plan. By the engineer working in limestone,
sandstone or slate, but little interest may be taken in
granites, basalts and other igneous materials, or vice
versa. Such engineers can, therefore, now secure a
guide to either or to both groups, according to their taste
or requirements. It is needless to say that these books
are thoroughly suitable for the purpose they are intended
to fulfil. ‘ They deal with rocks from a purely geological
point of view. Their object is to convey a theoretical
rather than a commercial knowledge of rocks, and their
study should form ‘ the preliminary foundation before
further reading upon economic lines. Many so-called
“ experts ” suffer from knowing too little of the
theoretical side of the question, which is frequently quite
wrongly despised as having no practical value. We
could, however, from our own limited experience alone,
fill several columns of this journal with examples of the
practical application of theoretical geology in engineer-
ing construction. Whether it is a question of the
petrography or petrology of rock masses, sound practice
•must always be based upon theoretical knowledge, and

we cordially recommend these two volumes to the
attention of all who wish to find an explanation of many
of the facts open daily to their observation in the course
of their daily routine.

MAGNIFYING THERMOMETERS.

It is frequently the case that thermometers are fixed
in inaccessible positions, with the result that tempera-
tures are not checked as regularly as should be the case,
due to the inconvenience of reaching the instruments.

Messrs. T. Sugden Limited, of 180, Fleet-street,
London, E.C., have been supplying lately magnifying
thermometers which enable the temperatures to be read
with ease from a considerable distance, due to the scale
and mercury column being magnified. The illustration
shows a comparison between one of the many types of
magnifying thermometers supplied by this firm and an
ordinary thermometer such as are frequently adopted.
The placing of a lamp (electrical, gas, or any other

THERMOMETER
SOCKET

Usual Pattern. Magnifying Type.

Comparative Illustrations of an Ordinary
Thermometer and of Various Types
of Magnifying Thermometers.

illuminant) behind the scale facilitates still further the
reading of the thermometer, but the daylight falling
upon the back of the scale is found as a rule ample to
make easy the reading of the thermometer from quite a
distance.

The magnifying thermometers, in addition to the
above-mentioned vital advantages, it must be pointed
out, are of robust construction, accurate, and constant.

The magnifying thermometers are supplied by
Messrs. T. Sugden Limited in a great variety, with
ranges of scales up to 1000 degs. Fahr., with straight
or right angle stems, with steel or brass pockets, or
flanges for screwing on pipes, tanks, etc.; in fact, they
can be modified to suit practically all purposes.

Timber, etc., for Collieries and Important Industries.—
The English Forestry Association wish it to be known that
they will do everything possible to organise supplies of
native timber and forest produce from the various districts
in the British Isles, and assist collieries and industries where
necessary, to obtain timber which they require. The
association has been for some time taking steps to organise
the native supplies for collieries and other purposes, and
they possess special facilities for pointing to the most likely
sources of supplies. They willingly place all facilities and
information free of cost for the benefit of consumers or of
the timber and other trades, and wTill act as a centre for all
enquiries as to native timber. They invite all those
interested in the production, sale, conversion, or consumption
of timber to co-operate with them in the present crisis, and
send particulars as to timber or goods which they wish to
purchase or to sell, or stocks of converted or unconverted
timber which they hold. They will then place buyer and
seller in touch with each other, and leave all negotiations
to be conducted direct between the parties interested. They
wish to emphasise that they are not a trading association,
and do not buy or sell timber or goods, or charge commis-
sion or fees. Their work has been always to encourage the
use and demand, and to organise supplies of the native
timber, and assist home industries, but leaving it to recog-
nised channels to negotiate and supply the demand. They
would point out that there are large supplies of nearly all
kinds of foreign and native timber at present available.
They hope that there is no cause for alarm in any quarter,
and they wish to help as far as they can where any diffi-
culty is experienced. All communications should be
addressed to the Hon. Secretary, English Forestry Associa-
tion, Farnham Common, Slough, Bucks.