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THE COLLIERY GUARDIAN.

April 13, 1917.

CURRENT SCIENCE

A Specific Gravity Balance for Gases.

Mr. J. D. Edwards describes an apparatus designed
by the United States Bureau of Standards for the
accurate determination of gas densities, especially for
the use of the natural gas industry where the measure-
ment of gas by means of orifice meters requires a
knowledge of the density of the gas. (See Technologic
Paper No. 89, United States Bureau of Standards.)
An investigation by this Bureau of the effusion type of
apparatus, which has been generally used for this pur-
pose, but which has proven unreliable in practice, has
shown the need of more precise methods. To supply
this need, the present method was adopted, and suit-
able apparatus designed. The principle of the method
employed is based upon the laws of the compressibility
(Boyle’s law) and the buoyant effect of gas. The
balance contains a beam which carries on one end a
relatively large globe and on the other a small counter-
weight; the beam is enclosed in a gastight chamber.
The buoyant force exerted upon the globe is propor-
tional to the density of the gas, and therefore to its
pressure. Therefore, if the buoyant force exerted
upon the globe is made the same as shown by its posi-
tion of equilibrium when it is suspended successively
in two different gases, then the densities of the two
gases must be the same at these pressures, or the
specific gravity is the inverse ratio of the pressures.
In operation, the balance case is filled with air and
the pressure adjusted until the beam balances. It is
then filled with gas, and the pressure required to
secure a balance is determined in the same way. The
apparatus described provides a quick, accurate means
of determining gas density. The balance beam is sup-
ported on two needle points, which give high sensi-
bility. The needles are easily adjustable and in cdn-
trast with the metal or quartz knife edge usually used,
can be obtained almost anywhere, are inexpensive, and
can be replaced as often as necessary. The success
obtained in the use of this apparatus is mainly due to
the high sensibility afforded by this means of support.
It is necessary to remove the beam from the case only
when it is desired to transport it. No levelling bottle
is necessary in adjusting the gas pressure within the
balance, this being accomplished by means of a needle
valve which affords precise control. A portable outfit
is described, which combines lightness of weight, con-
venience in use, and durability, without any great
sacrifice of accuracy. No preliminary calibration of
the apparatus is necessary. The results obtained with
this balance were compared with those obtained by a
direct weighing method, and it was shown that an
accuracy of 1 or 2 parts per 1,000 could be obtained
quickly and without elaborate precautions.

Development of the Optical Glass Industry.

According to an article in the British Journal of
Photography (vol. Ixii., No. 2949, p. 607), the all-
important distinction between optical and other ordi-
nary glass is not merely one of composition, but one
of quality as well; it must be homogeneous and free
from striae. The method of producing such glass was
discovered about 1807, and its successful manufacture
accomplished about 1814, Guinand, a Swiss, being
credited with the first conception of the method, and
Fraunhofer, a Bavarian, with the development of its
application. Through Guinand’s sons the secret of
the method of manufacture found its way into France,
and eventually into England. The manufacture of
optical glass in the former country began to be
imported about 1829, and in England (by Chance
Brothers) about 1848, and those two countries rapidly
obtained the lead in the industry. Prior to the dis-
covery. of the right method of making optical glass,
opticians had to be content with merely selecting the
best samples of glass they could find from material
made in the ordinary fashion, in consequence of which
only small lenses could be produced. The discovery
of the right method of manufacture enabled Fraun-
hofer to produce lenses of nearly 10 in. in diameter,
whereas the further improvements made by Chance
Brothers, in England, led to the production of 29 in.
lenses in 1855. Just about the time when Fraunhofer
succeeded in mastering the mechanical details of
optical glass making, he discovered a method of test-
ing the optical qualities of glasses of different compo-
sition, and of expressing these qualities in figures. In
1804 Wollaston discovered the black lines in the colour
spectrum, which were afterwards called Fraunhofer
lines. In 1814 Fraunhofer applied the spectroscopic
method to the testing of the optical qualities of glass,
and promptly applied the results to' the production and
examination of new varieties. Up to that time only
two varieties of glass were in use for optical purposes
—crown and flint. With regard to the discovery that
a combination of crown and flint lenses could be
achromatic, Dolland is generally assumed to have been
the originator in 1757, though Chester Morse Hall
produced the first achromatic telescope in 1733, and
there is evidence that the credit properly belongs to
Hall. Out of this discovery eventually grew a demand
for more varieties of glass, for with the simple crown
and flint only a limited correction was possible. At
first only the visible rays needed correction, and with
the advent of photography the invisible rays required
correction to secure a sharp photographic result.
Colour work has made further demands, and practi-
cally requires that the lens be corrected for the whole
of the visible spectrum. Fraunhofer having found
means to test glass, set about this task, but his early
death stopped further progress.

The deficiencies of flint and crown achromatic com-
binations were recognised, and numerous attempts
were made to produce suitable glasses, but the diffi-

AND TECHNOLOGY.

culties and expense of the work handicapped and dis-
couraged all experimenters on a small scale, and little
real progress was made. When Abbe and Schott, how-
ever, showed their willingness to undertake the work,
at Jena, a liberal Government enabled them to carry
the matter through, and, as the result of a vast number
of trials and tests, they produced glasses well adapted
to the manufacture of achromatised lenses. The
example of Schott was followed closely by Chance in
England and Mantois in Paris, and at the present day
optical glasses of great variety are obtainable. It
should be noted that Fraunhofer should fairly receive
the lion’s share of credit due to those who have helped
to develop optical glass. His early demise only, in
all probability, prevented him from completing the
results later achieved by others with virtually the
same materials as were used by him in his early work.

Formation of Clinkers in Boiler Furnaces.

Mr. A. A. Cary, writing in the Electrical. World
(vol. Ixix., No. 6, p. 267, February 10, 1917), says that
during many years’ experience in designing, testing,
improving, and operating furnaces, used for many
purposes, he has found no branch of this subject that
requires more consideration than the troublesome for-
mation of clinkers in the furnace and the formation
and growth of clinkers on furnace linings. In most
cases this trouble can be either greatly reduced or
avoided, for clinkers are formed by the fusion of the
ash and refuse which remain after the combustion of
the coal in the furnace. Ash is really a very useful
material in the furnace when it is properly, taken care
of there; since, with proper thickness of ash covering
the top surface of the grate, the burning and warping
of the bars are prevented. Where properly designed
shaking bars are used, the thickness of the ash bed on
the top surface of the bars can be easily regulated, and
it is very necessary that this be properly accomplished
with this type of bar, as most of the shaking grates are
designed with thin, delicate edges, which are easily
burned or warped when brought into contact with a
hot fire bed. It is quite essential that the thickness
of the ash bed should always be reduced before any
attempt is made to break up the fire bed above, other-
wise the ash will be thrown up into the bed of fuel and
fused into clinker. The shaking grate, improperly
used, may be productive of more clinker in the furnace
than would occur with the plain stationary grate in
use. The thickness and conditions of the fire bed have
much to do with this grate and clinker trouble, how-
ever. The density of the fuel bed is really of more
importance than its thickness. A comparatively thin
fire bed that is dense and compact will hold the ash
within its hot body, instead of allowing it to precipi-
tate to the grate bars, just as much as a thicker bed
when it is more open and porous. When any fire bed
is more or less solid or compact, the air for its com-
bustion will not pass uniformly throughout its mass,
but, on the contrary, this air will search out its
easiest paths of passage, and flow through the irregu-
larly scattered openings formed by cracks or holes in
the fire bed, and, with the ash held up in this densely-
packed bed, the air, rushing through these selected
positions, will cause intense combustion to occur at
such places, which rapidly fuses the surrounding ash
into clinker, and at the same time causes the soft,
pasty mass to attach itself to a considerable amount
of solid combustible fuel. Too thin fires carried on
the grates should be avoided, especially with shaking
grates, as every fire bed should be of sufficient depth
of ash to be carried on the bars to protect them from
the intense heat of the burning fuel above them.
Excepting these very thin fire beds, it may be said
that the intensity of draught required to operate a
furnace is, generally speaking, a measure of its clinker
making properties, which is another way of saying that
the intensity of the draught required is a measure of
the density of the fire bed.

Manganese Steel Castings.

Mr. W. S. McKee, writing in the Iron Trade Review
(vol. lx., No. 7, p. 413, February 15, 1917), says that
manganese steel was developed originally in England,
largely through the efforts of Sir Robert Hadfield. It
has been manufactured on a commercial scale for
nearly 26 years. The first manganese steel castings
made in the United States were turned out in 1892.
Originally it was considered impossible to make man-
ganese steel castings successfully weighing over a few
hundred pounds, but at the present time large rolling
mill pinions, crusher heads, and similar castings weigh-
ing up to 30,000 lb. each are being produced regularly,
and it does not appear that the limit of weight has
been reached by a considerable margin. As manufac-
tured at present, manganese steel is similar in analysis
to ordinary converter metal, except that it is high'in
carbon and unusually high in manganese. In ordi-
nary commercial castings the proportions of the latter
metal range from 11 to 13J per cent. This combina-
tion of constituents gives the finished castings certain
distinctive physical properties. Heat treatment is a
very essential part of the process. The necessity for
heat treatment limits the thickness of section which it
is possible to cast successfully. Originally the castings
were made with comparatively thin sections, but
researches during the past few years have made it pos-
sible to increase the thickness of section, so that at
present castings with walls up to 5| in. in thickness
are handled satisfactorily. Manganese steel made by
Robert W. Hunt and Company, Chicago, has an elastic
limit of 53,4001b., tensile strength of 108,4001b. per
sq. in., an elongation of 33-7 per cent, in 2 in., and a
reduction in area of 38-6 per cent. This steel does not
owe its wear-resisting qualities to its hardness. When

subjected to the Brinell test, it shows an average hard-
ness number of 200. The electrical resistance of man-
ganese steel is about 3-4 times that of ordinary
Bessemer steel. It is non-magnetic, and advantage is
taken of this property in the use of this material for
shields or bottom plates of lifting magnets. If the
castings require finishing, special equipment is neces-
sary. Ordinary machining methods are unsuccessful,
and grinding must be employed. Holes more than
| in. in diameter are cored and ground to size. • When
it is necessary to drill smaller holes or to cut threads,
soft steel or wrought iron inserts are set in the moulds
at desired points like chaplets, and the metal is cast
around them.

New Method of Charging Storage Batteries.

In a recent United States patent (No. 1205620),
Varian M. Harris, Chicago, Illinois, the inventor,
gives an interesting theory of the apparent inefficiency
observed when charging storage batteries from rectified
or pulsating circuits. In the charging of a storage
battery, an appreciable time element is necessary for
the chemical reactions to take place within the battery,
and for that reason if a phase wave is cut at the points
which correspond in voltage to the voltage of the
battery, the latter will not be charged, since it does
not respond instantaneously to the current which passes
into it, and sparking will result.

In order to overcome this difficulty, the phase waves
should be cut at appropriate points, so that the
rectified current passes to the battery at a voltage con-
siderably below the normal voltage of the battery. The
chemical changes immediately begin to take place in
the battery, and by thus allowing the current to flow
to the battery at a decreased voltage, the chemical
changes have become sufficiently started so that when
the voltage of rectified current reaches the normal
voltage of the battery, the rectified current is allowed
to flow to the battery. This result is accomplished by
constructing the segments of the mechanical rectifier
of such a width that the phase waves of the rectified
current are cut at a voltage sufficiently below the
normal voltage of the battery that the time during
which the rectified current is increasing up to the
voltage of the battery is sufficient to overcome the
electrolytic lag of the latter.

THE LATE LORD ALLERTON.

As briefly reported in our last issue, Lord Allerton
(Kight Hon. \V. Lawies Jackson), chairman of the
Great Northern Railway Company, died in London on
April 4, at the age of 77. At the age of 17, the death
of his father left Lord Allerton in control of a bank-
rupt tanning business, and he at once set himself to
revolutionise the methods employed, and in a few
years had created a flourishing commercial concern.
His thoroughness in that respect was characteristic of
his manifold activities in private and public work.

He was member of Parliament for North Leeds from
1880 to 1902, when he was raised to the peerage. He
was Financial Secretary to the Treasury in 1885-86,
and again occupied tha.t position from 1886 to 1891,
when he became Chief Secretary for Ireland. But it
was as chairman of the Great Northern Railway Com-
pany that he was best known. It was while occupying
the position of Mayor of Leeds in 1895 that he was
invited to the chairmanship, as successor to the late
Lord Colville of Culross. Lord Allerton was on the
boards of the East Lincolnshire Railway, the Eastern
Telegraph Company, and the Forth Bridge Railway,
being also trustee of the Submarine Cables Trust. He
presided oyer a number of Commissions, of which we
may specify particularly the Royal Commission on Coal
Supplies (1901-5). The work of this Commission
greatly transcended that of its predecessor, and the
chairman showed throughout his qualifications for
handling the most diverse matters in a practical
manner.

His heir, the Hon. George Herbert Jackson, was
born in 1867, and was educated at Rugby. The
younger son, the Hon. F. Stanley Jackson, now a
director of the Great Northern Railway, is the well-
known cricketer.

Uruguay and United States Coal. — The Uruguayan
Department of War and Marine has appointed a Com-
mission to report on the merits of the United States coal
known as “New River Admiralty Smokeless Coal.” A
supply of 1,500,000 kilogs. of coal is needed for the fleet,
and as the United States coal is quoted at a lower rate
than Cardiff coal, the New River coal will be purchased if
the committee makes a favourable report. The Diario
Official also announces the appointment of a committee to
look into the project of installing boilers for consuming
oil on the steamer “ Uruguay.”

Increased Freight Rates for Neutral Tonnage.—It is
announced by the Central Executive Committee for the
Supply of Coal to France and Italy that the rates of
freight for neutral steamers are as follow from April 9 :
(1) From east and west .coast of Great Britain to North
French ports not south of Brest, an advance of 12s. per
ton on existing rates, z’.e., schedule rate plus 50 per cent,
plus 12s. per ton. (2) From east and west coast of Great
Britain to Bay ports south of Brest, an advance of 18s.
per ton on existing rates, i.e., schedule rate plus 50 per
cent, plus 18s. per ton. (3) From east and west coast of
Great Britain to French Mediterranean schedule ports and
to West Coast Italy. No rates are fixed, but brokers are
to submit to the local committee best offers for considera-
tion of the Inter-Allied Chartering Executive. The
increased rates are not to affect the chartered freights of
vessels covered under old war insurance previous to the
April 9 increase.