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upon a feeble continuous spedrum, a charader of spec-
trum which seems to point to a probably unstable condi-
tion of the atmospheres of these stars.

The large difference of position of the bands in the two
groups of stars is much too great to admit of an explana-
tion founded upon a possible orbital motion of the stars.
Besides, the near coincidence of Dr. Copeland's measures
of two bright lines common to the stars 4001 and 4013
shows that the difference of position of the blue band is
not due to motion in the line of sight.*

If future observations should show that the bright
blue groups are variable, we must look, it would seem,
to causes of a physical or a chemical nature.

If the two bright groups, differing in position by about
X 0040, belong to different substances, or, less probably,
perhaps, to different molecular conditions of the same
substance, it is conceivable that one or other substance,
or molecular state, may predominate and appear brilliant,
according to certain unknown conditions which may pre-
vail in the star's atmospheres*

It might be suggested that both bands are due to a
long group of bright lines extending from about X 461 to
X47X, and that this long group is cut down by absorption
bands ; in one pair of stars an absorption from the green
cuts off the less refrangible part of the long group down
to about X 467, while in the other two stars the more re-
frangible part is eclipsed, and the bright group appears
as in 400Z.

The appearance of the spedra in our instruments
scarcely seems to us to be in accordance with such a
view, because, though we did susped brightenings in the
alternate places, the appearance of th.: spedrum was not
such as to suggest a bright group dimmed by absorption,
for in that case the amount of absorption needed to all
but obliterate a group, as bright as it appears in the
other pair of stars, would have blotted out completely the
relatively feeble continuous spedrum. This continuous
spedrum, though faint, was still distindly seen.

More observations are needed, but it appeared to us
desirable by these suggestions to invite the attention of
observers to the points in question.

As the main objed of our examination of these stars
was to determine whether the bright band in the blue
was to be regarded as showing the presence of carbon by
its coincidence with the blue band of the hydrocarbon
flame, we were not able, from the pressing claims of
other work, to extend our examination to many other

* Dr. Copeland permits me to give the following measures of the
bright lines in the Wolf-Rayet sUrs, which were made by him and
Mr. Lohse on January 28, x6iB4;~


+35*4001.. —

+35" 4013.. 58a-4(a)

+36** 3956.. 581*0(2)

xst yellow 2nd yellow Bright
line. line. line.


Large bloe

568-9(2) 54«*<Ha)

5aao(x) 469*5(3)
- , 4f5-4(a)

Digitized by



Wol/ and Rayet^s Bright'Line Stars in Cygnus.


I Jan. 23, 189X.

points in connedion with the spedrum of these faint
stars, for an exhaustive examination of which, indeed,
our instruments are not sufficiently powerful.
^ We have stated already that the fairly luminous con-
tinuous spedrum reaches up to the bright band in all
three stars, and extends beyond into the violet, as far as
the eye could be expeded to follow it.

The spedra are weakened at many points by what
appear to be absorption bands, and are crossed by several
brilliant lines, the positions of some of which have been
given by Vogel and by Copeland.

An examination with spedroscope B of some of these
bright lines, as they appear under small dispersion,
showed them to be really not single lines, but short groups
of closely adjacent bright lines.

One of the brightest of these lines is found in the star
No. 4013, at the position, according to Vogel, of X 570.

Dr. Copeland's measure for this line is \ s6S'g in star
4013, and X 570*4 in the star 3956.

As this position is not very far from that of the green
pair of sodium lines at X 5687 and X5681, it has been sug.
gested that the line in the star is due to sodium, though
there is no line of comparable brightness in the star's
spedrum at the position of the dominant pair of the sodium
spedrum at D. *

On confronting in spedroscope B the star line with the
green sodium lines, the bright space in the star's spec-
trum was seen to consist of a short group of several bright
lines close together, and nearly equally bright. This
group appeared to extend through about four times the
interval of the sodium pair, which would make the length
of the group about X 0024. The green sodium lines cross
the group at about one-fourth to one-third of the length
of the group from its more refrangible end. The group in
the star is rather less bright at the two ends, but there is
no gradual shading off in either diredion, as in the case
of a 6uting.

When we examined this part of the spedrum with the
small dispersion of a prism of 45**, we were pretty sure of
a feeble bright line, less refrangible than the pair of bright
groups in the yellow, and not far from the position of D.
We were not able to see this line in spedroscope B with
sufficient clearness to enable us to fix its position. It
may be D, or, perhaps more probably D3.

In No. 4001, Vogel saw a line at the position of the P
line of hydrogen. It is probable that this line, as is the
case in so many stars in which it appears bright, is vari-
able, as we were not able to see it when the H/S line from
a vacuum tube was thrown in. In the similar star D.M.
+37" 3821. as we have stated already, the F line of hy-
drogen was very bright.

We were unable to deted in any of the stars a
brightening of the spedrum at the position of the chief
line of the bright-line nebulae. For this examination, the
lead line at X 5004*5 was thrown in, and the continuous
spedrum of the star near to this position carefully

In their original paper. Wolf and Rayet state that they
were not able to deted any nebulosity about the stars.
They say :— ** Elles ne prdsentent non plus aucune trace
de n6bulosit6 " (loc. cit., p. 292).

In a recent paper, Mr. Keeler, the Lick Observatory,
confirms this view. He says : — '* At my request, Mr.
Bumham and Mr. Barnard examined the Wolf- Rayet
stars in Cygnus for traces of surrounding nebulosity, but
with only negative results."

Notwithstanding these negative results, it appeared to
us of great interest to ascertain further if any nebulosity
would come out in a photograph of the stars taken with a
long exposure.

* The 570 line is most probably the green sodiuTn line 569, the ab-
sence of the yellow sodium being explained by the half-and-half ab-
sorption and radiation mentioned in the discussion of the causes
which mask and prevent the appearance of a line in a speAruii
(Bakerian Leaure (or z88a, Roy. Soc. Proc., vol. xliv., p. 41).

Mr. Roberts responded at once to our wish when we
asked his invaluable assistance, and on November i8t«
1890, he took a photograph of this region of Cygnus, with
an exposure of two hours.

The three stars come out strongly upon the plate, but
there is no nebulosity to be seen near any of them. There
are faint stars in close proximity to the three stars, and
apparently surrounding them, and, in the case of No.
3956, six of these faint stars are seen close to it, in an
apparent spiral arrangement.

Though this surrounding of faint stars should be pointed
out, it should, at the same time, be stated that the whole
neighbouring region is so densely studded with similar
faint stars that it would be rash, perhaps, at present to
suggest that this apparent connedion of the bright-line
stars with faint ones near them may be other than acci«

Professor E. C. Pickering informs me *' that photo*
graphs have been obtained at the Harvard College Ob-
servatory of all the stars hitherto discovered whose spedra
consist mainly of bright lines and are of the class dis-
covered by Rayet. Part of these have been photographed
at Cambridge, and the remainder in Peru." He states
that they may be divided into three sub-classes, according
to the charaders of the bright lines. He says, further :-—
** Photographs of the spedrum of fifteen planetary neboUe
have also been obtained. They resemble closely the
spedra described above, except that the line 500 is
strongly marked ; 470 is seen in most of them, while the
lines due to hydrogen are also bright."

It would seem that Professor Pickering*s photographs
do not permit him to distinguish the different positions of
the bright blue band in some of these stars, for he gives
for all the stars the same position, namely, \ 470.

We regret that the insufficiency of our instrumental
means has left our examination of the spedra of tJiese
stars less complete than we could wish. Our observations
appear to us, however, to be conclusive on the main ob-
jed of our enquiry, namely, that the bright blue band in
the three Wolf-Rayet stars in Cygnus, and in D.M. +37®
3821, is not coincident with the blue band of the Bunsen

By Professor VIVIAN B. LBWBS.

When carbon is aded upon at high temperatures bv
steam, the first adion that takes place is the decompose
tion of the water vapour ; the hydrogen being liberated,
while the oxygen unites with the carbon to form carbon
dioxide, thus : —

Carbon. Water. Oarbon dioxide. Hydrogen.

C + 2(HaO) = COa + 2Ha
The carbon dioxide so produced inter ads with more red-

* [M r. Roberts has furnished os with the following description of
the stars as they appear on his photograph : —

"No. 400X appears as a multiple star made up of one bright, two
fainter, and one very faint star partly behind the others ; there is
also a fourth bright star close to the multiple star. The group ia
surrounded by at least eight faint stars within a radial distance of
-J-86" of arc from centre to centre.

" No. 4013. — The photo-image of this star is made up of three
stellar images touching each other in a line slightly curved. Two
are bright and one faint ; and there are indications of two other faint
stars behind the two bright ones. This multiple image of four or
five stars is surrounded by five bright and seven faint stars; all
within a radial distance of 82" of arc measured from centre
to centre of the multiple star. The multiple image measures
-^53" in length and J[-i9" in breadth,

•• No. 3956.— Its photo-image is ±27" in diameter. It is encircled
by three stars of lesser brighttress, and six faint ones within a radial
distance of 59", i.e., there are nine stars within a radial disUnce of

♦ Abstra^ of the Cantor Le^ures delivered at the Society of Arts
Commaoicated by th^ Author,

Digitized by



Jan. 23, 1892. I

Gaseous tllutninants.


hot carbon, forming the lower oxide, carbon monoxide,

COa + C = aCO.
So that the completed rea^ion may be looked upon as
yielding a mixture of equal volumes of hydrogen and
carbon monoxide — both of them im6ammable, but with
non-luminous 6ame8. This decomposition, however, is
rarely completed, and a certain proportion of carbon di-
oxide is invariably to be found in the water-gas, which,
in pradice, generally consists of a mixture of about the
following composition : —

Hydrogen 48'3i

Carbon monoxide 35*93

Carbon dioxide 4*25

Nitrogen 875

Methane .. .. 1*05

Sulphuretted hydrogen .. .. i*ao
Oxygen 0*51

The above is an analysis of water-gas made from gas
coke in a Van Steenbergh apparatus. The ratio of carbon
monoxide and carbon dioxide present depends entirely
upon the temperature of the generator and the kind of
carbonaceous matter employed. With a hard, dense,
anthracite coal, for instance, it is quite possible to attain
a temperature at which there is pradically no carbon di-
oxide produced ; while with an ordinary form of generator,
and a loose fuel like coke, a large proportion is generally
to be found. The sulphuretted hydrogen in the analysis
quoted is, of course, due to the high amount of sulphur to
oe found in the gas coke, and is pradically absent from
water-gas made with anthracite. The nitrogen is due to
the method of manufadure, the coke being, in the first
instance, raised to incandescence by an air-blast, which
leaves the generator and pipes full of a mixture of nitro-
gen and carbon monoxide (producer gas), which is carried
over by the first portions of water-gas into the holder.
The gas so made has no photometnc value — its con-
stituents being perfedly non -luminous ; and attempts to
use it as an illumioant have all taken the form of incan-
descent burners, in which thin ** mantles " or ** combs **
of highly refradory metallic oxides are heated up to
incandescence. In the case of carburetted water-gas the
gas is only used as a carrier of illuminating hydrocarbon
gases made by decomposing various grades of hydrocarbon
oils into permanent gases by heat.

Water-gas generators can be divided into two classes :
(i) Continuous processes, in which the heat necessary to
bring about the interadtion of the carbon and the steam
is obtained by performing the operation in retorts exter-
nally heated in a furnace. (2) Intermittent processes, in
which the carbon is first heated to incandescence by an
air-blast, and then, the air-blast being cut off, superheated
steam is blown in until the temperature is reduced to a
point at which the carbon begins to fail in its adion, when
the air is again admitted to bring the fuel up to the
required temperature ; the process consisting of the alter*
nate formation of producer gas with rise of temperature,
and of water-gas with lowering of temperature.

Of the first class of generator, none, so far, have as yet
been pradically successful in England.

Of the intermittent processes, the one most in use in
America is the Lowe, in which the coke or anthracite is
heated to incandescence, by an air-blast in a generator
lined with fire-brick ; the heated produds of combustion,
as they leave the generator and enter the superheaters,
being supplied with more air, which causes the combus-
tion of the carbon monoxide present in the producer gas,
and heats up the fire-brick baffles with which the super-
heaters are filled. When the necessary temperature of
fuel and superheater has been reached, the air-blasts are
cut off and steam is blown through the generator, forming
water-gas, which meets the enriching oil at the top of the
first superheater, called the ** carburetter," and carries the

vapours with it through the main superheater, where the
finng of the hydrocarbons takes place. The chief advan-
tage of this apparatus is that the enormous superheating
space enables a lower temperature to be used for the
fixing, which does away, to a certain extent, with the too
great breaking down of the hydrocarbon, and consequent
deposition of carbon^

The Springer apparatus differs from the Lowe only in
construaion. In the former the superheater is direAly
above the generator, and there is only one superheating
chamber instead of two. The air-blast is admitted at the
bottom, and the producer gases heat the superheater in
the usual way; and when the required temperature is
reached, the steam is blown in at the top of the generator,
and is made to pass down through the incandescent fuel.
The water-gas is led from the bottom of the apparatus to
the top, where it enters at the summit of the superheater,
meets the oil, and passes down with it through the
chamber, the finished gas escaping at the middle of the
apparatus. This idea of making the air-blast pass up
through the fuel, while in the subsequent operation the
steam passes down through it, is also to be found in the
Loomis plant, and is a distind advantage — ^the fuel being
at its hottest where the blast has entered ; and, in order
to keep down the percentage of carbon dioxide, it is
important that the fuel through which the water-gas last
passes should be as hot as possible to ensure its redudion
to carbon monoxide.

The Flannery apparatus is also only a slight modifica-
tion of the Lowe plant ; the chief difference being that,
as the water-gas leaves the generator the oil is fed into
it, and with the gas passes through a Q-shaped retort
tube, arranged round three sides of the top of the gene-
rator. In this tube the oil is volatilised, and passes with
the gas to the bottom of the superheater, in which the
vapours are converted into permanent gases.

The Van-Steenbergh plant stands apart from all other
forms of carburetted water-gas, in that the upper layer of
the fuel itself forms the superheater, and that no second
part of any kind is needed for the fixation of the hydro-
carbons. This arrangement reduces the apparatus to the
simplest form, and leaves no part of it which can choke or
get out of order — an advantage which will not be under-
rated by anyone who has had experience of these plants.
While, however, an enormous advantage is gained there
is also the drawback that the apparatus is not at all fitted
for use with crude oils of heavy specific gravity, such as
can be dealt with in the big external superheaters of the
Lowe class of water-gas plant, but requires to have the
lighter oils used in it for carburetting purposes. This
which appears at first sight to be a disadvantage, is not
altogether one, as, in the first place, the lighter grade of
oils, if judged by the amount of carburetting property
they possess, are cheaper per candle power added to the
gas than the crude oils; while their use entirely does
away with the formation of pitch and carbon in the pipes
and purifying apparatus — a fador of the greatest import-
ance to the gas manufadurers. The fad that light oils
give a higher carburation per gallon than heavy crude oils
is due to the fad that the crude oils have to be heated to
a higher temperature to convert them into permanent
gases, and this causes an over-cracking of the most valu-
able illuminating constituents. This trouble cannot be
avoided; as, if a lower temperature is employed, the
result is the formation of non-permanent vapours, which,
by their condensation in the pipes, give rise to endless
trouble. The simplicity of the apparatus is a fador which
is a considerable saving of time and expense, as it reduces
to a minimum the risk of stoppages for repairs ; while the
initial cost of the apparatus is necessarily low, and the
expense of keeping it in order pradically nil.

In such an apparatus, 1000 cubic feet of carburetted
water-gas having an illuminating value of 22 candles can
be made with the consumption of about 30 lbs. of coke or
anthracite, and 2*5 gallons of light naphtha.

The great objedton to the use of carburetted water-gat

Digitized by



Gaseous llluminants.

I Jan. 23t X891.

is undoubtedly the poiaonona nature of the tarbon mon-
oxide, which ads 1^ diffusing itself through the air-cells
ol the lungs, and forming with the colouring of the blood
corpuscles a definite compound, which prevents them
carrying on their normal fundion of taking up oxygen and
distributing it throughout the body and at once stops life.
All researches on this subjed point to the fad that some-
thing less than i per cent only of carbon monoxide in air
renders it fatal to animal life; and this, at first sight,
seems to be an insuperable objedtion to the use of water-
gas. It has, indeed, influenced the authorities in several
towns— notably Paris— to forbid the introdudion of water
gas for domestic consumption. It would be well, how-
evei', to carefully examine the subjed and see, by the aid
of aQual figures, what the risk amounts to compared with
the HSks of ordinsry coal gas. Many experiments have
been made with the view of determining the percentage
of cfarbon monoxide in air which is fatal to human, or,
rather, to animal life ; the most reliable, as well as the
latest, results being those obtained by Dr. Stevenson of
Ouy*S Hospital, after an investigation instituted in con-
sequence of two deaths which took place at the Leeds
Forge, from inhaling uncarburetted water-gas containing
40 per cent of carbon monoxide. Dr. Stevenson found
that I per cent visibly affeded a mouse in ij minutes, and
killed it in an hour and three quarters; while o'x per cent
was highly injurious. Taking, for the sake of argument,
the last figure as being a fatal quantity, so as to be
well within the mark, it is found that in ordinary car-
buretted water-gas, as suplied by the superheater pro-
cesses such as the Lowe, Springer, and others, the usual
amount of carbon monoxide is 26 per cent ; but in the
Van Steenbergh gas, for certain chemical reasons to be
discussed later on, it is generally about 18 per cent, and
rareljr rises to 20 per cent. An ordinary bedroom is 12 ft.
by 15 ft., and zoft. high; and therefore it will contain
z8oo cubic feet of air. Such a room would be lighted by
a single ordinary batswing burner, consuming not more
than 4 cubic feet of gas per hour, and if this were left full
on, in one hour the 1800 cubic feet of air would be mixed
with four-fifths of a cubic foot of carbon monoxide (the
carburetted water-gas being supposed to contain 20 per
cent), or 0*04 per cent. In such a room, however, if the
doors and windows were absolutely air-tight and there
were no fire-place, diffusion through the walls would
change the entire air once in an hour. Therefore the
percentage would not rise above 0*04, while in any
ordinary room imperfed workmanship and an open
chimney would change it four times in the hour, and
reduce the percentage to o'oz— a quantity which the most
inveterate enemy of water-gas could not claim would do
more than produce a bad headache. The point under
consideration, however, was the use of carburetted water-
gas as an enricher of coal-gas, and not as an illuminant
to be consumed fir s$ ; and it might be calculated that it
would be probably used to enrich a i6-candle coal gas up
to 17-5-candle power. To do this, 25 per cent of 22candle

rer carburetted water gas would have to be mixed with
Taking the quantity of carbon monoxide in London
gas at 5 per cent (a very fair average figure), and 18 per
cent as the amount present in the van Steenbergh gas,
we have 8*25 per cent of carbon monoxide in the gas as
sent out— a percentage hardly exceeding that which is
found in the rich cannel gas supplied to such places as
Glasgow, where it Is not found that an unusual number
of deaths occur from carbon monoxide poisoning. More-
over, carisuretted water gas has quite as strong a smell as
coal gas, and can be quite as easily deteded by the nose.
The cost of most of these methods of enriching coal
gat can be calculated, and give the following figures as
VM coit of enriching a z6-candle gas up to zy's-candle
power per zooo cubic feet :—

By cannel coal 4d.

By the Maxim-Clark process . • . . 2/0^*

By the Lowe or Springer water gas . . x^d.

By the Van Steenbergh water gas • • }d.

In adopting any new method, the mind of the gas
manager must, to a great extent, be influenced by the
circumstances of the times ; and the enormous importance
of the labour question is a main fador at the present mo-
ment. With masters and men living in a strained condi*
tion, which may at any moment break into open warfare,
the adoption of such water-gas processes would relieve
the manager of a burden which is growing almost too
heavy to be borne. Combining, as such processes do, the
maximum rate of produdion with the minimum amount
of labour, they pradically solve the labour question. The
cost of paraffin oil of lighter grades, and the fear that the
supply might be hampered by the formation of a huge
monopoly, has been a great drawback; but we have mate-
rials which can be equally well used in this country, and
of which an almost unlimited supply can be obtained.

At three or four of the Scotch iron-works, the Funiace
Gases Company are paying a yearly rental for the right
of colleding the smoke and gases from the blast-furnaces.
These are passed through several miles of wrought*iron
tubing, gradually diminishing in size from 6 feet to about
18 inches ; and as the gases cool, there is deposited a
considerable yield of oil At Messrs. Dixon's, In Glas-
gow, which is the smallest of these installations, they
pump and colled about 60 million feet of furnace gas per
day, and recover, on an average, 25,000 gallons of fur-
nace oils per week ; using the residual gases, consisting

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