es Tore


93 nae os . - - ; \ TM EN it ed at the Post Office of New. York, N. Y., as Second Class Matter Charles Allen Mann, President, 461 Broadway, Sew York raht 10, by Mupn & Co, ine Published weekly by Munn & Cu inc., at 461 Kroaagway, New York. Frederick Converse Beach, Sec y and Treas., 361 Broadway. New York,

Scien ific American, established 1845. j Th ~ >IT” wh p P { Scientific American Supplement, $5 a year. Scientific American Supplement, Vol. LXX., No. 1813. NEW LK, OCTOBER 1, 1910. ) Scientific American and Supplement, $7 a year.

& |

fi H






Ovcrover 1, 1910




A vew principle is used in the Leblanc refrigerating machine, and we wish to point out the advantages which can be obtained by the use of this apparatus, as vell as to indieate the method of working It is invented by a French engineer and is constructed by the European Westinghouse company It will be noted with interest that the new system is being used by the French nav for some of the new battleships in



order to carry ut he cooling of the ammunition storage quartet Smokeless powder having nitro- cellulose a i base is now recognized as likely to be decomposed at a high temperature, and when the heat is too great there will often be an explosion This is tated to be the reason for the explosion of the battle- ship Jena is well as other vessels. Accordingly the navy department is installing plants on board the new battleships such as the “Danton” and the “Vol- taire 3 as to give a circulation of cold air in these


We are familiar with the usual methods of cooling

in a given locality, and this is generally carried out by the use of piping in which a non-freezing brine circulates When the brine returns to the freezing

machine it has been heated by a few degrees and the

maAchine again lowers the temperature to the standard degree In plants where the cold is produced by com- pressed and liquefied gas, this latter circulates in a worm within a tank filled with the brine, and the ex- pansion of the gas within the worm causes the cooling


* , i onder ne renversée f d

Pompe centrifuge m, extraction

bany coienke

Eau . chaude


effect upon the liquid. Generally we use ammonia, methyl chloride or carbonic acid gas for this purpose. The new Leblanc system makes a new departure in using the rapid evaporation of water in order to secure the cooling. Water presents a distinct advantage, see- ing that the ones just mentioned give a heat of vapori- zation ranging from 200 to 88 calories per kilogramme (2.2 pounds) at 0 deg. C. (freezing point), while for water the figure is much higher; this being 606.5 calories. For equal weight, water thus is much super- ior for cooling, but it has not been used in practice for

practical plants, seeing that we must operate at a low temperature near the freezing point or below it But here the vapor of water has a very low tension so that a small weight of such vapor occupies a great volume. This is not the case for the above-mentioned liquefied gases, seeing that their boiling point lies far below the freezing point of water

To give a low enough temperature by the use of evap- oration of water we therefore required to draw off a large volume of water vapor, and none of the present apparatus is suitable for such use. We will see how n M. Leblane’s device. He uses the

this is obtained vacuum pump which he invented in the first place for use with steam engine condensers. Referring to Fig. 1, it is composed of an inlet cone A and an outlet cone B. In the upper cone is a reversed turbine working at a very high speed, and it delivers cold water from the upper to the lower part at a rapid rate. Exhaust steam from the engine enters at F and the steam is drawn off

and condensed at the same time Such a device is called a “condenser pump,” and in such form it is used in small plants. For larger plants M. Leblanc prefers the apparatus shown in Fig. 2. Here the water is not delivered at high speed, but it enters at A and falls down in drops The exhaust steam comes in from

above rhe same “condenser pump” as above shown is now placed outside of the condenser column at C, and

it draws off the air saturated with vapor by way of B

Saumure & vive - relradir A


and evacuates it at D along with the water coming from the turbine. A second pump of the usual rotary type, FE, serves to take off the water from the interior of the column, and in practice the turbine C and pump £ are both mounted on the same shaft so as to give a very compact plant.

The above system is applied to cooling machines in the following way: Instead of having the cooling brine cooled off by the evaporation of a liquefied gas, we now cool the brine by the evaporation of a part of its water alone, this being carried out by a vacuum formed by the “condenser pump. As shown in Fig. 3, the brine enters at the top at A, and a perforated plate B causes it to fall in fine spray in the evaporator C, in which the vapor is kept at a low pressure—1l1 millimeter (0.0394 inch) of mereury. Such partial vacuum is caused by the ejector EF and the “condenser pump” placed at H. The ejector is a perforated nozzle ZF in which is sent live steam from above, and the vapor coming from the brine is aspirated in through the small openings in the nozzle as shown by the arrows. Such vapor is diffused in a lower cone F, and it is con- densed and taken off by the “condenser pump” placed below. At J is a pump for the circulation of the brine, and it works on the same shaft with the “condenser

pump.” Inside the column a jacket D is used so as to retain the spray and keep it away from the outlet pipe so that particles of water cannot be drawn off. The cooled brine collects at the bottom of the column and is taken off by the pump.

Our illustrations (Figs. 4 and 5) show the applica- tion of the Leblanc system at the Bethune mine and metallurgical establishment in France. It is here used in obtaining the benzo] from the gas coming from coal distillation. Coke for metallurgical purposes is obtained from such distillation. In order to remove

the benzol from the gas this latter is treated with tar oil, the oil being dropped in a shower from the

top of a cylindrical tank, while the gas is sent at the bottom in the usual way. The oil thus absorbs the benzol, but as it becomes heated by the gas it }): ede to be cooled by sending it through a worm cooler placed in a water tank. Means must be provided for cooling the water so as to keep it near 15 deg. C. (59 deg. F.). The present refrigerating plant serves this purpose and also operates a small ice producer. One of our views, Fig. 4, shows the two large main evapor- ating columns, one for the brine for the water cooling

and the second for the brine which is used in the ice¢ machine Separate columns are needed here, seeing that the brine is used at two different temperatures for these two purposes,

On one side is the larger column used for the ater- cooling brine and on the other a smaller column of the same type for the ice machine. Each column has a steam ejector of the kind we mentioned (FF in Fig. 3). Such steam, mixed with the water evaporated from the brine, is not however directly taken off by the “condenser pump,” but it passes first into a condenser of the kind seen in Fig. 2. This condenser is common

Fie. 6.—LEBLANC’S EJECTOR-CONDENSER ENGINE POR RUNNING THE WATER TURBINE. (See section Fig. 1.) View of Leblanc’s ejector-condenser turbine in smaller engraving, Turbine is run by small engine here show

to both ejectors, and is seen on the left hand of the photograph, Fig. 4. Below it is the “condenser pump,” which is the same as C in Fig. 2. Instead of live steam for the aspirating nozzles, there is used exhaust steam at about one atmosphere pressure coming [rom the different engines of the plant. The electric moto! on the left serves to operate all the four pumps on the same shaft, these being the air pump for the con- denser, the Leblane “condenser pump,” also the two brine pumps of the columns

Referring again to the plants installed on the French battleships (Figs. 7 and 8), the main li! of

these are as follows: An air current is sent through the chambers, and this air has a continuous « ila- tion, returning to a cooling apparatus from which it is again sent out, this by the use of an air fan. The cooler is a chamber where the air passes alons set of wing tubes or hollow plates in other cases rhe tubes and plates contain a cooling brine which «iret lates within them by means of a pump, and the »rinv is cooled in the same way as we have just seen an evaporating tank and steam aspirator, usil the method employed at the Bethune works, that is sur- face condenser and then a Leblanc “condenser np.” What is special to the battleship plant is tha has a light construction in steel plate, and this gal-

or sea water

vanized for all parts where the brine

c i

Ocrorer 1, 1910,

comes in ontact with it. In cold weather, sea water itself can used for the cooling Instead of the brine. Here the sea water is passed but once through the air- cooler, and is then returned to the sea, this by suitable piping. uur pumps worked by electric motors are employed liere.

To illustrate other uses for which the new system js adapted we show (Fig. 9) a view of a plant recently installed in a large glue and gelatine works at Nan- terre, France. Here we require the cooling of a gela- tin sol mn so as to have it rapidly take the form of a jelly-like mass. The solution is run out on a long table i! thin layer. Over it is a strong air current, and the air works in a closed cycle, being cooled in a refrigerating room by a brine solution. The brine is kept cold in the same way as above, using an appa- ratus Which is modified in some parts in order to suit

the present needs.


almost disappearing into the limbo of things

AFT! forgotten the two-cycle engine seems to be awaken- jing to a new life. In the quite early days of oil en- gines the Day cycle was invented. Whether Mr. Day was the true and original inventor. we need not trouble to discuss; the cycle he used is known as the Day cycle ust as the ordinary four-cycle is called after Otto, though the honor is certainly due to Beau de Rochas The Day engine, as everybody knows, had an

exhaust which was overrun by the piston, and

an admission port on the opposite side of the « ylinder.


A charge drawn into the crank chamber and com- pressed there to a few pounds, rushed through the admission port, impinged against a baffle on the pis-

after striking the the remains of the Nothing could

ton, was deflected upward, and cover turned down again, driving

products of combustion out before it.

be simpler; no exhaust valves were wanted, and the admission valve on the crank chamber was a very sim- ple thing. But the engine had its defects. First and

foremost was the uncertainty as to the direction in

which it would go. If automatic ignition were em- ployed, as was often the case, a slight change in the some small hot spot in the combustion cham- hot gases remaining in the cylinder, might premature firing, either pulling the engine up suddenly or starting it off in the opposite direction. The method of purging the cylinder was far from per-

fect The

mixture, her, or the


incoming charge not only did not succeed

n driving out all the products. of combustion, but

some of it itself escaped. The consequence was that the charge was weak from adulteration with burnt gases, and the economy bad because some of each charge was lost through the exhaust. Moreover, leak-

chamber past the bearings, and

Hence the engine, though


loss of fuel.

age from the so on, caused

apparently able to do twice as much as a four-cycle of

the same cylinder volume, did nothing of the kind, and it showed little, if any, advantage in power for weight, and was certainly uneconomical. Later on,

= =



A. Steel plate covered evaporator with perforated cover for falling brine,

from exhaust ¢

when the

D gasoline engine came into general use, the y cyel with various modifications, again came

forward, and although it is not now used on cars, a 00d many Dloy it. Her, A little ga ber, with tl and the engi: But, as y

mall marine sets, mostly American, em- another disadvantage is liable to arise.

Oline finds its way into the crank cham-

‘esult that the mixture becomes too rich, stops.

have said, in spite of all these troubles

* The Engineer,

aaa * MRE eENE penibaathiid tied nape INSTALLATION


and disadvantages the Day cycle has continued to attract of course in a modified form vices turned into a virtue. This other than the old-time proclivity of the engine to re-

By careful train-

inventors, and it is actually coming back into

use with one of its old

virtuous-vice is no

wanted to.

verse when it was not

ing it has now been taught to go backward only at request. As a result it promises to take a very im- portant place in marine engineering, for the diffi-


culty with the four-cycle engine has, of course, always been the complicated reversing gear. There have nat- urally been other modifications, most notable of which in the method of exhausting. The

scavenging is ef-

is an improvement is still partially or

overrun preserved, but



wholly by pure air admitted

through special valves, or through a cylinder wall port as in the Day engine, instead of wholly by the new charge. Economy is thereby secured. In some

cases, as, for example, the Diesel two-cycle engine, all

chance of premature explosion is prevented, because

the oil is not admitted until compression is complete burns as in the ordinary an engine is ef- Peck engine the

In the mentioned it Diesel The fected with great simplicity. In the products of combustion are driven out partially by the and partly by


cycle. reversing of such

entering at the from the crank chamber; in the Bolinders and the scavenging is effected by crank chamber air, and the oil is driven by a pump into the vaporizer time during the stroke In all these cases the waste of charge through the ex- what It is prob-

incoming charge top, pure air other types

some compression

haust has. been obviated, but it is not clear to degree of perfection scavenging is carried ably, at least in those engines which depend upon the piston baffie for the deflection of the air, not as com- plete as in the Otto cycle, and less power per stroke On the other hand, the

much to com-

may therefore be anticipated. simplicity of the method that minor

the improvement

great has so disadvantages outweighed,

in running effected by a


mend it Moreover,

TY A ST Mn | il iT + ‘_ WT ee WUT



B, Conical hood for keeping out water


, and a surface condenser as described in A B, Fig. 2.

better turning moment, pernitting the use of a smaller fly-wheel, is a material point in marine engine design.

The two-cycle engine, it will be seen, presents, then, many advantages for marine work, but it still labors under one drawback. It depends in most cases, both for starting and reversing, good supply of highly compressed air. the pump which supplies that air or of any tion between the air reservoir and the cylinders would

existence of a The failure of

upon the


cngines, of course, highly for the cycle, and is not as a supply employed for maneuvering purposes only.


1813. 211

render the engine practically useless. In Diesel type

conipressed air is necessary quite in the same position

But even it could do with far less receiver volume,

and would be simplified all round, if other means ol

reversing could be found. In one engine reversal is by slowing the engine, and then advancing the spark so that firing takes place before the dead

point. This is a simple method, but some skill is re-

quired or the engine may stop altogether, and there is

the further objection that the explosion takes place against a moving rapidly, and may set up heavy stresses. It is desirable to be able to stop and start the engine either direction with absolute certainty, and so far the only sound method There


from rest in

of doing that is by the use of compressed air.

is room for invention to improve on it. RUBBER-SEED OIL.

Ir was a long time before the oil of cotton seed be- came a valuable commercial factor. It is now be lieved that the oil of the rubber seed will in time be a marketable product and profitable busi- ness in the Malay States.

At present there seeds for planting purposes that the supply does not This office has received a request shipped to the Philippine order cannot be filled until next The Botanic Gardens at Singa-

develop a

is such a demand for the Hevea equal the demand. Para seeds to be Islands, but the October or November.

pore, which is really the birthplace of the rubber in-

for 5,000

Malaysia, and which has furnished great

quantitles of seeds to the plantations, reports that it

dustry in be able to furnish another 5,000 order of rub before spring, many booked. So rubber-seed oil is out of The surplus of planted in the Far East, and

will not

ber seeds next owing to the

orders already when

time is coming

from the 0

the question at present.

there will be a large seeds

millions of trees already

then the rubber-seed oil will have its day and its valuable market.

It is now suggested by experts that, owing to the future commercial value of rubber-seed oil and the

residue obtainable from local treatment, it would be

wise in erecting new machinery on plantations or re modeling old machinery to make provision for power and space for the convenient placing of the rubber- seed crushing machines. This would leave the residue

which it is believed by experts will


on the estates,

prove good for cattle food, as well as a fertilizer. Scientific value of the Hevea seed have proved that they yield a

inferior to

investigations of the commercial

fine, clear oil of good drying quality, not

the best linseed.—From Consul-General James T. Du

Bois, Singapore.

It is reported in the American Machinist that the


Union Pacific Railway has commenced a plan for in- creasing the efficiency of its men by means of a cor- respondence school. This school is intended for men of all grades, and its main object is to make them more capable in their present work, as well as to fit them for better positions. It is also arranged to allow for men to study for other departments in some cases, and the instruction is in charge of officers of the com- pany. This should tend to bring the officials closer to the men, which is much to be desired in all cases,


Ocroner 1, 1916,



Tre various accidents which have occurred recently to aeroplanes raise the whole question of whether the construction of the wings is such as to give the requisite margin of safety to insure their not breaking under the loads which are likely to come upon them in use. Up till recently the fatal accidents had mostly occurred in connection with biplanes, and there was never any suggestion that the cause of the accident was want of strength in the main wings. Lately, however, several accidents have occurred to mono planes, in which there is good reason to think that the cause of the accident was the collapse of the wings in mid-air and of the consequent fall of the machine. It is, of course, very difficult in the case of aeroplane accidents to ascertain which part broke first, for the fabric is generally so utterly smashed by contact with the ground that no details of the first breakage can be seen Further, the aviator, who is the only man who cen tell accurately what happened, is generally killed, so that the only information available is what can be seen of the fall while the machine is in the air, and accidents occur so suddenly that different peo- ple do not always get the same impression of the sequence of events. There seems, however, little doubt that in several cases the wings collapsed in some way while the machine was flying, and that it fell in consequence, This feature is so important that it is worth while considering the whole matter of the strength of the main planes

In the case of a biplane the framing of the main vings usually consists of four longitudinals running ihe whole length of the wings, and these are braced together, bo‘h vertically and horizontally, with numerous cross-struts and wire diagonals, so as to give them very great strength, both vertically and horizontally In fact, if one works out the stresses of the diagonal wires, it is found to be very much below that usual in ordinary engineering work, and the wires are so numerous that, even if one of them breaks from vibration, the extra stress thrown on the adjacent ones will not bring the load up to the ordi- nary stresses allowed in girder work. The horizontal trength is also practically equal to the vertical, as the trussing is generally of the same character.

When we come to the monoplane, however, we find that the trussing is of a much simpler character, and further, that there is often no horizontal trussing at all Figs. 1 and 2 show the front view and plan of the framing of an ordinary monoplane It will be seen that the vertical strength of the main plane is entirely dependent on the stays, generally four each side, which go to the bottom of the strut under the backbone. Should one of these break, the probability is that the wing will collapse with disastrous results. fn our issue of November 5th, 1909, we referred to the fact that these stays are often single parts of steel vire or ribbon, and that this is a material which has not been found sufficiently reliable for use as supports to the masts of small sailing boats, where wire-rope is always preferred, 6n account of the warning it gives before breakage. Wires in tension driven fast through the air are liable to vibrate in such a way as to deteriorate the metal, and it appears therefore that to trust to single strands is exceedingly risky; there is not this objection to the single wires on the biplane, as these are so numerous that one of them breaking should not endanger the structure. The risk in the monoplane could be avoided either by using wire-rope with a large margin of safety, or by having such a number of stays that a single one breaking will not endanger the whole structure

A much greater defect in the wings of many of the monoplanes, however, appears to be the lack of hori- zontal strength. It is, no doubt, assumed that the weight of the machine rests on the wings, and that this is the main stress to be provided for. This is no doubt true, but a careful consideration of the horizontal stresses will show that these are much greater than might at first sight appear. When flying horizontally the horizontal stress cannot, of course, exceed the thrust of the propeller, and must in prac- tice be considerably less than this, as part of that thrust is spent in overcoming the resistance of the body of the machine, the tail, ete. The ratio of lift- ing power to horizontal stress will vary considerably in different machines with the efficiency of the planes, but even with the machine flying horizontally the horizontal stress will probably be in the neighborhood of 10 per cent of the vertical

It appears, however, that there are circumstances in which the horizontal stress may be very much greater than this, for it increases with the speed of the aeroplane through the air, and this may be very much greater when descending than when flying level. The wings contribute the greater part of the air resist-

ance, and, therefore, if the aeroplane is descending, it will accelerate till the horizontal stress on the wings balances the acceleration due to gravity. Thus, if the aeroplane descends at a slope of one in five, the hori- zontal pressure on the planes may be approximately 20 per cent of the weight of the machine. If the engine is kept running, it will be more than this by the amount of the propeller thrust. It is quite clear, therefore, that circumstances might arise in which the horizontal stress would be some 25 per cent of the vertical.

Now, if we examine the framework of many of the monoplanes, we find that the horizontal strength of the wings is nothing like 25 per cent of the vertical; in fact, it is often probably under 5 per cent. The frame- work of the wing consists of two longitudinals, and

Fig.2. ~ ai E <= =——s >>. ; he BY]? Bs Be J G wailed



numerous cross-battens carrying the fabric. The longi- tudinals are the only part fixed to the backbone, and therefore take practically the whole stress. These longitudinals are generally made very deep in propor- tion to their height, and are often channeled on the sides to make them into I-section girders. It is obvious, therefore, that their horizontal strength is very small indeed compared with the vertical. True, the numer- ous cross-battens stiffen the wing perceptibly, but the extent to which this is the case can hardly be calcu- lated; and as they are often only about % inch by 4 inch, and fastened with very small nails, they cannot be relied on to any great extent. It seems, therefore, that either the wings should have diagonal bracing or should have stays in front corresponding to those down below. Where the backbone projects a long way in front of the wings, the latter method might be the simpler, as at A A, Fig. 3. Alternatively, diagonal wires may be run in the wings, as at B B, Fig. 4; and this is sometimes done—e. g., in the “Demoiselle.” Another plan might be to make the battens them- selves a diagonal trussing by having them at an angle to the main span, and making those on the top slope one way and those at the bottom cross them. This might, however, introduce difficulties in making the surface smooth enough.

That the question of speed in descent is a matter for which provision should be made is shown by the fatal accident at Rheims, The speed in this case would

be higher than when flying level, and that in some cases the horizontal strength of the wings appeared to provide a very small margin for this increased stress, and the accidents seem to have happened exacily as suggested, for, in each case, when rapidly des: nding from a height the wings collapsed.

It may be said that when descending the engine should be stopped and the descent made at a speed not exceeding that which can be maintained on the level, but it is hardly practicable to stick to this, and if the aeroplane is to be of any practical use, it must be made to stand any reasonable usage to which it is likely to be subjected. Bicycles and motor-cars are often run down hill, or before a wind, at speeds far higher than could be maintained on the flat, and it is quite certain that a machine which is unsafe under these circumstances is not fit for ordinary work. Most men run down a hill as fast as they can without losing control of the machine, and aviators will doubt- less do the same. The machines must, therefore, be made to stand the stresses set up under these condi- tions.—Engineering.


THe Times correspondent at the Lanark Meeting was invited by Mr. Grace to share his ascent in a Farman biplane. The following is the record of his experience:

The first wind register showed the velocity to be from 25 to 30 miles an hour, but toward half-past 1 o'clock it dropped to 18 and 22. The competition for this period was weight-carrying round the course, each machine to carry 350 pounds. By virtue of my weight of 14 stone (196 pounds) I was invited by Mr. Grace to share his adventure in a wind that warned off all other competitors. The worst part of such a journey for the novice is the waiting until everything is ready for the start. The sensation of anticipation is not un- like the feeling that one has when one is waiting for a wounded boar to break cover from the corner into which he is driven. But once the propeller starts to whirl behind you aW other thoughts beyond exhilara- tion of rapid motion vanish. You have gripped the struts thinking that you will have to hold on like grim death, but you immediately find that this is not neces- sary. The machine moves along the ground at an ex- traordinary pace, and | only knew that it was actually flying when I saw the elevating plane change from the horizontal. Of the motion of flight it is difficult to speak clearly. Even in the high wind that Mr. Grace was now climbing, it was not more than the sensation of a beautifully balanced motor-car. The earth—in this case the sward of the Lanark racecourse—seemed to be racing away from under us, and in a flash we were level with the first pylon and the judge's box.

The machine was now up to 150 feet, and I became engrossed in Mr. Grace’s method in flying. It seemed to me that his attention was glued to his elevating plane, with just momentary glances out of his eye to judge the distance by which he had to shun each pylon in its turn. We were now crossing fields and water. | could observe the gates, the wire fences, and a man bathing in the water. Then we were round into the wind. Our pace immediately slackened, and Mr. Grace was working to keep his machine in the air. As we crossed a road we were going so slowly that | could observe the direction of the hoof marks of a horse that had recently passed. Here all observation ceased, as Mr. Grace was now battling with the wind. We had only 500 yards to traverse to cross the winning line, but the dead weight against the wind was bringing the machine down. Then there came a gust heavier than them all. It took the machine just up the requisite amount to cross the line, and we came gently to earth. It had only been a four minutes’ ride, but it was cer tainly the most delightful ride that I had ever experi- enced, The only recollection that I have that will describe the general sensation is that of exquisite motion.—The London Times.

It is stated that Messrs. Vickers, Sons & Maxim are to lay down an experimental tank for testing ship models at their works at Barrow-in-Furness. Such 4 step should meet with well-deserved success. Many firms have considered doing the same, but at present only Messrs. Denny and Messrs. John Brown )sse5s establishments of the Froude type, though the /’»rsons Company at Newecastle-on-Tyne have an open-ai’ tank in which to try models. Probably other firm will eventually realize the advisability of laying down e*

perimental plants, if only because of the saving possi- ble in trial trip expenses, which in the case of ne¥ scien-

designs may often greatly exceed the cost of th tifie investigation that would have obviated them.


some ed to Tress, 'y as iding

igine peed | the and inust it is are ; far it is nder Most hout ubt- be ndi-

ting na



Ocrozer 1, 1910.






THe report that the Krupp firm has acquired an option on the patents of the Swedish Colonel Unge for aerial torpedoes, and the experiments which the firm has carried on with these projectiles, have re- awakened interest in a weapon which possessed great military importance until the middle of the nineteenth century, namely, the rocket. The high estimation of the rocket, however, was made possible only by the inferiority of artillery in general, and it neces- sarily disappeared as soon as the value of rifled cannon had been recognized.

The rocket is the simplest device by which an explosive charge can be carried to its goal. Instead of

~ ah > i .




——— l\

His Ne

\ SS

Yj vA 4 Y 4 Yj 4 4 Z 4 Z ry Z y | | 1 % Y Y y U t

A Bb Dd BR Fie. 1.—ROCKETS. A, Rocket with inclined vanes. B, Hale’s rocket with lateral gas out-

lets, C. After end of Hale’s turbine rocket. D, Turbine, E, Section of turbine channels,

a heavy cannon, which requires horses for its trans- portation and a large crew of men for its service, the rocket needs only a light and inexpensive stand, from which it can be discharged by three men. As the propelling charge burns gradually, the propulsive effect is small at first, and increases during the first half of the flight. The rocket starts without the slightest shock, and consequently the walls of the hea’, containing the explosive charge, May be very thin, and a very large quantity of explosive can be carried, if it is desired to produce a conflagration or the effect of a mine. This freedom from sudden shock at the start also makes possible the employment of explosives which are more effective, but also more sensitive to shock than black powder. This prin- ciple was subsequently employed in America in the construction of the pneumatic dynamite gun. Little success, however, has been obiained with this arm. Freedom from shock is less important with modern explosives, which, though very powerful, are not easily exploded.

the rifled cannon quickly caused the rocket to be abandoned, except as a luminous projectile.

The uncértainty of aim was caused chiefly by the stick, which was attached to the head for the purpose of carrying the center of gravity as far back as pos- sible, in order to increase the steadiness of flight. This addition, however, increased the total surface, and hence increased the air resistance and the effect of wind. When the rocket was directed against the wind its range was shortened, because the end of the stick was lifted and the head depressed, and in a wind blowing from one side the rocket was deflected toward that side. Deviations of 250 and 300 paces have been observed, with a moderate wind and a range of 2,000 paces. Numerous attempts were made to remedy this defect by substituting for the stick some device which would assure greater regularity of flight. For example, inclined vanes were attached to the after part of the head, for the purpose of causing the projectile to rotate in consequence of the pressure of the air upon these vanes. (Fig. 1, A.) With the same object, Hale in England constructed a rocket in which the gases escaped through oblique openings. (Fig. 1, B.) This device was subsequently improved by


substituting for the oblique lateral orifices a sort of turbine or screw at the end of the rocket. (Fig. 1, OC, &.)

No appreciable improvement, however, was effected by these modifications, as the flight of the projectile was still influenced by the varying rate of evolution of the gas and the varying strength and direction of the escaping streams. Uniformity of these factors is required to produce steadiness of flight. The packing and pressing of the explosive in the propulsion cham- ber did not produce perfectly regular combustion, and

Propulsion chamber


Turbine section


This gradual increase of velocity makes the efficiency of the rocket greatest at great distances, for the maxi- mum velocity is attained at about the middle of the course. Beyond this point the combustion gases do hot acquire sufficient pressure in the increased space lef! vacant by the combustion of the explosives to Produce the same reaction as before. When we remem- ber that rockets have attained maximum velocities of 700 feet per second and ranges of 4,000 to 5,000 Paces, the great value of rockets in the time of their employment becomes apparent. The most serious de- fect of the rocket was its uncertainty of aim, in which respect was inferior even to the smooth-bore gun. It was owing to this defect that the introduction of

the direction of the escaping streams of gas continu- ally changed in consequence of the fusion of the metal around the orifices. The principal source