[So many new firms are now entering the aeroplane industry, and in consequence so many trained engineers are for the first time taking a serious interest in aeronautical engineering, that the moment seems an opportune one in which to give a general review of the principles of aeroplane design. THE AEROPLANE has been so fortunate as to have obtained permission from Mr. F. S. Barnwell, who until recently held an important position with the British and Colonial Aeroplane Company, Ltd., of Bristol, to publish a treatise read by him lately to the Engineering Society of Glasgow University. Mr. barnwell is best known as the designer of the highly successful Bristol "tabloid" scout, in which work he had the benefit of the practical experience of the Bristol Co.'s chief pilot, Mr. Harry Busteed-now Flight-Lieut. R.N.A.S. Mr. F. S. Barnwell has himself recently been given a commission in the Royal Flying Corps, and promises to be a pilot of the same class as his brother, Mr. Harold Barnwell, of Vickers Ltd.

The editor of this paper does not profess to understand Mr. Barnwell's calculations, but as he has proved himself a practical man by turning out one of the best machines in the world, and as he has further shown remarkable ability as a pilot, the editor accepts his figures without question, and presents the first instalment of this important document with complete confidence that it will interest and instruct many engineers who have hitherto regarded aeroplanes merely as haphazard agglomerations of sticks, wire, and canvas, which are propelled by a singularly noisy and unreliable engine and are held together chiefly by hoping for the best. With this slight introduction readers are left to Mr. Barnwell's mercy.-Ed.]

AIR PROPELLER

petrol consumption at full normal power; in the sixth, the same for lubricant; in the seventh, weight of suitable mounting and suitable shields or "cowling"; in the eighth, weight of suitable air propeller with coupling; in the ninth, tenth, eleventh, twelfth and thirteenth columns we have total weight of motor (complete as in col. 4) with mounting, cowling, propeller, petrol, lubricant and tanks, for 2, 4, 6, 8 and 10 hours, running respectively at full normal power.

As to how the figures in this table are obtained. Weight of motor complete is given us by the makers, likewise the power, revs., and petrol and oil consumption. The weight of a suitable mounting is a matter for working from the actual weights of satisfactory mountings for known cases. I have assumed that weight of mounting varies directly as weight of motor, and from such data as I have, have taken it as 17th weight of motor for a rotary, and 1-10th weight of motor for a stationary engine.

The weight of "cowling" I have taken as varying as the square root of the weight of the motor, and as equal to twice

FROM DENMARK.

The Danish correspondent of THE AEROPLANE sends the following interesting notes concerning aviation in the Eastern War area. So far, all we have heard from that side has been the eternal silly bragging of the "Morning Post's" irritating correspondent at Petrograd, according to whom the Russian aviators who are admittedly very good, even if poorly equipped dominate the whole atmosphere, as, according to him, the Russian troops dominate the earth. It is, therefore, both refreshing and salutary to have a slightly different, and, certainly, a more technically accurate, description of aeronautical operations on that front. As usual, our correspondent's work is left untouched ::

"Berliner Tageblatt" published some lines of a letter from a flight officer:-"Today I am able for the first time to tell you of my adventures. Our work is quite different from that carried out by our comrades on the western front. While most of their flights are small, we have to carry out special petrol flights of a length of 200 km. to 300 km. Hitherto, we have not seen much of the Russian aviators, and the few ones, which were observed, did not venture to cross the German lines, but watched from the distant, and the Russian flight captain who crossed the frontier by the little west Prussian city Strasburg, had only lost his bearings. All the Russian aviators fly French Nieuport or Farman aeroplanes, and nothing has been seen of the giant Sikorsky biplanes. When we conquered Eydtkuhnen again, or more correct in the Russian neighbouring city Kibarty, we found then a number of French aeroplanes and Gnome engines, which had been left by the Russians on their flight.

"Till now I have only once had a fight with a Russian aviafor: it was in the morning after the battle of Gumbinnen,

square root of weight of motor in lbs. for a rotary, and onehalf this weight for a stationary motor.

The weight of tanks I have taken as varying directly as the capacity, and as 1/5th of the weight of the contents (when full, of course), taking petrol as 7.2 lbs. per gallon, and lubricating oil at 10 lbs. per gallon.

The weight of propeller I have taken as varying as the square root of the horse-power and as equal to three times square root horse-power in lbs.

All these weights are fair ones from such data as I have come across. You will understand that they are only approximate, but they are accurate enough for first estimate of weights, and probably err on the safe, that is, the heavy, side.

From this table, then, we can get the total weight of power plant for a considerable number of different powers and for any length of maximum power running between the extreme limits of present requirements.

(To be continued).

with

when our troops withdraw in the direction of K8,000 prisoners. I was ordered to find out whether the Russians followed, and then with how big troops. Scarcely had I flown in Eastern direction for one hour, when I observed a Russian aviator on a Nieuport monoplane, who kept to Westand 300 feet below me. He flew straight at my aeroplane, which did not trouble me at least. I rose some hundred feet on my quickrising Taube monoplane, let the Russian pass below and continued to learn how he would behave. Scarcely some kilometers had been covered when my observator told that the Russian aviator had turned 100 and flew in the same direction as I. So even I turned at once, and now we approached each other, only that I flew again some hundred feet higher than he. Now I flew in the direction of our aerodrome, when we saw that the Russian aviator had turned once more and rising, flew in pursue of us. When 600 feet off him and still 300 feet above I gave my passenger a token to fire, and got pleased to see him grasp the bullet carabine-the revolver could not have covered the distance. Scarcely had lieutenant Rfired, when the Russian turned quick and flew off in the direction of his positions, likely believing us to carry a machinegun on board. We went in pursue till being above the Russian troops, and in spite of their bullets and shrapnells bursting much lower, we found out the direct number of their troops and the direction of marching. One and a half hour later we reported the exact news of our watching to the headquarter in T——.

"If the Russian aviators have only made few patrol flights hitherto over our troops, the Russian troops try to trouble us, whenever possible. If we arrive above Russians on march, they stop at once, gather and open a heavy fire, which has however caused no losses of men till now. Only two aeroplanes of a slow

rising type were brought down, but both aviators and observators could flee to rescue through the neighbouring woods. But not through fire alone the Russians try to trouble or make our watch impossible; when they had learnt that we used to undertake patrol flights in the mornings and evenings only, they only marched between the hours from 9 to 12 and 2 to 4 o'clock. But we found these facts out quick, and so flew of course just at these times. Then the Russians quite altered their march order, as the luggage was brought forward during the nights, and the troops, leaving the roads, marched through the fields by daytime, which we found out in turn too.

"This morning an officer was sent out on a patrol flight from our aerodrome to watch the Russians approaching in eastern Prussia; he flew deep into the country and reported of a quick approaching division. To learn further details three of my fellows were sent out, but returned without any; they had flown along the roads without seing men. Then I was ordered to start a patrol flight more than 300 km. in length, to find out whether the advanced division had withdrawn again. Carrying only petrol for hours I determined to economize and not to follow the big roads, but to cut off right angles, and when, about 10 km. off the road I happened to look down through, I saw a village, that had grown quite grey, and descending some hundred meters in spite of the shower of bullets fired at us, we found the village full of soldiers, and even through the field-paths tight snakes of Russian soldiers in grey uniforms massed towards the German frontier. This was the division, which some hours before my fellow had seen advancing on the road to W. And so we found almost always later the Russian troops marching through the field-paths.'

A "Feldpostbrief" reports the following adventure of two German flight officers :-"L. and I had been ordered out on a patrol flight above the advancing positions of the Allies in North, and had started on our old brave biplane, which had gone through several adventures already; a thick fog covered the earth so that you almost wanted to cut pieces off with your knife to have a look. Thus we were compelled to fly low, guided by the compass, and when the weather cleared somewhat in half an hour, we descended cautious from a height of 2,000 metres. True, below there were black stripes and points on the light ground, which must mean troops on the road. I circled wide above the enemy, while L. drew up their positions. They had observed us however, and soon the wellknown little white clouds appeared. Only musketry fire! And my observator continued his work without letting himself trouble. Behind a wood we found out several columns. He asked me to descend somewhat to facilitate the observation. Now the left plane is hit by some bullets, and suddenly a dull explosion sound from the petrol reservoir, and before I know the cause, the petrol indicator sinks quick, and pressure gauge rests at o. 'Alle Wetter'! the petrol tank has got hit, and next moment the turns of the engine slow. But already I have seized the petrol pump and forces fresh air into the tank as quick as possible, to keep the engine running, and thanks to God, the engine recovers. But now we have but to return, and about 50 km. separate us from the aerodrome. Anxious watching the petrol indicator, which reports the loss of the costly fuel, I bank and work the horizontal rudder, and obeying the biplane rises.

"For almost 20 minutes we flew in this way with all nerves strained, when the well-known puff came from the carburator, the token that there is no more petrol for the engine. Indeed, we hope to have the enemy behind, but still we are not to be denied, being forced to alight amidst a hostile population. Cautious I enter out of the fog cover and descend by a big city. What is to follow? The first curious already appear, making haste and in the distant shouting: 'Vive L'Angleterre.' I have a changing twinkle with L. Evidently they take us for Englishmen, and if we can stand the play of this part, we are able to get off again. So L. commences speaking a broken French, as do the real Englishmen, ordering petrol and a tinker. Soon we have both, and quicker than we could have hoped for, the leak in the petrol tank is soldered, fresh petrol taken in; some Zouaves having shortened our stay, lasting twenty minutes, they help us by the start. And so we could speed off at full turns of the engine, and from the height we dropped a visit-card to the pleasant fellows, with our best thanks for the assistance-but alas! in the German language."

Scandinavian aviators.

best

The last lists of the aerial war are reported thus in "Flugsport, December 23rd, 1914:-Casualty list. Feldflieger-department: Captain Geibel, wounded by aeroplane accident; Lieutenant Brock, missing; Sub-lieutenant Brinker, missing; aviator Krebs, wounded; aviator Vizefeldwebel Lucht, wounded.-HI. The Promised Invasion.

Sir Cecil Hertslet, the British Consul-General for Belgium, speaking on "The Siege and Fall of Antwerp" at the Eolian Hall, said the airship raid on Antwerp came unexpectedly when the streets were lighted as usual. After that the city was darkened, and when they had another visit from a Zeppelin the airship did not get nearer than the suburbs. Nobody was killed and no houses were destroyed. When so much was. said about the darkness of London, it was interesting to know that darkness did have a material effect in reducing damage and loss of life. It had been suggested that it was absurd to darken London, as a Zeppelin could come any moonlight night. But if it could come on a moonlight night it could also come by daylight. The object of a Zeppelin was to come at a moment when it was not likely to be seen. On the second occasion when a Zeppelin was signalled all the searchlights of the forts surrounding Antwerp were thrown on the Zeppelin. They could all see it, but it could not see them.

With this one can cordially agree, as also with the deductions of "C. W." in the "Observer" of Sunday, the 16th, in which h says that if the Zeppelins intend to come they will probably come during this week.

There is a growing moon to guide them at the start and they can arrive in complete darkness. They are more likely t come in a calm, or against a West wind, for in case of disablement of steering gear a West wind would drift them back to Germany, whereas an East wind would drift them farther into England and a North wind to France.

66 Mother."

An officer of the Garrison Artillery sends to a friend some verses which appeared in a recent number of a publication issued by the Fourth Division called "The Press Bureau." They are dedicated to the 9.2 howitzer, which the soldiers call "Mother," and according to this officer they "laud and somewhat accurately describe some of 'Mother's' exploits." The poem, which is about the best thing of its kind which the war has produced, appeared in the "Morning Post" of January 18th. A "Bosch" speaks:

"We've had a slight misfortune with a train

And I think we've every reason to complain,
It was full of gallant Prussians
Going to fight the nasty Russians,

When overhead there sailed an aeroplane.
Boom!! Mother!!?

We picked up several bits

Of the late lamented Fritz,

But we never saw the blooming train again.

"It's really very sad about the town

Where lived the Heir-Apparent to our Crown;
It was far from all the stenches
Which arise from dirty trenches,

And we thought the British aeroplanes were down.
Boom!! Mother!!!

We found the Kronprinz' braces,
But we can't find any traces

Of that Donner Wetter Blitzen Flemish town.

"We were loading up our celebrated gun
After firing Black Marias, one by one,
For after careful searches

We had found out two more churches,
When an aeroplane showed black against the sun.
Boom!! Mother!!!

And although the Kapten pines
Still we can't find any signs

Of our celebrated 'Black Maria' gun.'

A Revised Version.

The following excellent effort appeared in the "New Witness" on January 14th.

Mr. Charles Strachey, the author, first quotes the alleged "Hymn for Airmen" from the "Times," January 5th, 1915.

HYMN FOR AIRMEN.

(Set to Music by Sir Hubert Parry.)
Lord, guard and guide the men who fly
Through the great spaces of the sky,
Be with them traversing the air

In darkening storm or sunshine fair.
Thou who dost keep with tender might
The balanced birds in all their flight,
Thou of the tempered winds be near,
That, having Thee, they know no fear.
Control their minds, with instinct fit
What time, adventuring they quit
The firm security of land:

Grant steadfast eye and skilful hand.

Aloft in solitudes of space

Uphold them with Thy saving Grace,
O God, protect the men who fly
Through lonely ways beneath the sky.

M. C. D. H.

He then adds: "The above-quoted Hymn, though admirably suited for performance (if that is the right word) in time of peace seems hardly suitable at the present juncture; and if the petitions it contains were accorded without exception, the result might be most unfortunate. With a view of averting this danger, and in order to bring the work into harmony with existing conditions, I venture to suggest the addition of the following stanzas :

This prayer, O Lord, of course, applies

Only to us and our Allies;

The men upon the other side

Do not "uphold," or "guard," or "guide."

It is not hard, O Lord, to know

A "Taube" from a "Blériot":

Should Zeppelins attempt a flight,

Don't keep them with Thy "tender might."

Don't prosper the aerial work

Of German, Austrian, or Turk;
But give the impious fellows fits,
And smash them into little bits.

CHARLES STRACHEY. [One cannot imagine a finer way of knocking the bottom out of the appalling mixtures of sloppy sentiment and blasphemy which seem to pass muster in these days for religious poetry. -Ed.]

To Accelerate the War.

An officer on active service writes:-"I do hate the cheap papers on the war. I am sure this tends to stop recruiting.. The papers ought to put things as they are, viz., that we are up against a brave, determined, and ferocious enemy, who use their brains and are without any very nice scruples; that it takes the French, Russians and ourselves . . . all our time to match them, and that we want more men, and highly trained men-especially highly trained men-and every ingenious device and method that can be suggested, to defeat them." [One device one might suggest to the War Office and Admiralty is the purchase of the most effective aeroplanes only, without troubling about the products of highly paid and ineffective scientists.--Ed.]

Southampton and District.

On Thursday a naval aviator flew over the district on a land-going biplane, heading towards Hamble against a terrific wind, flying very high. Once a powerful gust caught it and actually drove it backwards.

On Monday Mr. Mahl tested a new Gnome-engined Sopwith seaplane, another of the successful scouts. This machine put up a good performance, the speed being wonderful for a seaplane. Another Sopwith scout made a good flight on Sunday, and going up Southampton Water it had a cold passage against a strong wind, but when the machine finally turned and proceeded to come back with the wind its speed would have made even Americans admit it was "going some.

was

On Sunday morning three land-going machines were seen. They were sighted at about two to three thousand feet, all flying against the wind in single file as though one chasing the other. Finally, two went on northwards and the other returned. This flight excited a great many people who really thought it was a German raider being chased by two British machines, and that probably is the reason why so many rumours are continually being spread about the country

of raids.