Philippe Lebon

Phillipe Lebon, sometimes written as Le Bon, was born into an officers family on 29 May 1767 in Brachy, Department Seine-Maritime (Normandy). He became a civil engineer (Engineer for bridges and roads), but studied also with great success fire engines, i.e. steam engines. While he was producing in the woods of Rouen tar for the French navy by distilling wood, he had the idea to make use of the gases that were a by product of the distillation. He moved to Paris and filed his first patent. [1]    

French patent to Phillipe Lebon

Very little information is available about the gas engine of Philippe Lebon as he died before he had a chance to build a prototype. He was granted on 28 September 1799 a patent with the title "New means to use combustibles more usefully, either for heat or light and to collect various products" ("Nouveaux moyens d'employer les combustibles plus utilement, soit pour le chaleur, soit pour la lumière, et d'en recueillir les divers produits").

As usual at the time the patent did not receive an official number. It was issued as a hand written document and is available from the on-line archive of the French Patent Office. The technology of carbonisation of wood to retrieve pitch, which Lebon claimed to collect as a side product, was already used by stone age people. However it seems that this patent is the first patent for an oven to collect gas from carbonisation of organic substances. One easy to implement application of this invention was to use the wood gas was for lightening purposes. With his invention Phillipe Lebon had laid the cornerstone for a big industry to come, without being able to benefit from his visionary ideas.



Addition to the Lebon patent

About two years after filing his basic patent Lebon then filed an addition to his patent in which he describes a gas engine fuelled by the distilled gases. For those who have difficulties to read the original handwriting we have to thank the French Minister home minister who published the full text in printed form 24 years later among other patent descriptions of machines. Thanks to the Google project a digitized copy of this book is available.

Although the digitized original document shows at the end a diagram of his oven, I could not find so far any drawing accompanying his addition to his patent. The drawing on the left is from a biography [1] that was issued 50 years after his death. I cannot judge if this is his original drawing or a drawing depicted by someone else after his death.

Addition Certificate for Lebon delivered 25 August 1801

The following is a translation of the printed version of the Additional Patent. The original language was sometimes hard to follow. We also need to understand that the document reflects the state of science at the time which does not reflect our knowledge of Chemistry and Thermodynamics today. Not correcting these type of errors I tried to make translation more easy to read. I also added paragraph numbers so that I can easily refer to certain paragraphs.



Addition Certificate [to a Patent]

Delivered 25 August 1801

Developments of the means just proposed for the more useful use of fuels.

[0001] Part of the fuel by combining with the caloric passes into the gaseous state, and here are some important observations in this regard.

[0002] Any substance that passes from the solid or liquid state to the gaseous state does so with energy; its expansive force obviously counteracts to the weight of the atmosphere, and would push back more considerable obstacles, if opposed to it.

[0003] In the gaseous state, this expansive force varies according to the degree of temperature: it results in an action and a reaction that the mechanics have admirably used in steam engines; these machines are driven by the expansive force of water vapor. Analogue machines could be constructed, which would be driven by the expansive force of the gases themselves, which are not reducible by cold or pressure. So far, this second kind of machine seems to have been disdained; however, in many circumstances it offers valuable advantages. The driving quality of the two kinds of gaseous fluids that we have just distinguished derives essentially from the variation in volume that tends to produce that of their temperature. These variations can be captured in different moments; and hence an infinity of ways of combining and employing these elements of movement exists. A second family of very numerous machines exist which can be set in motion only by variation of temperature.

[0004] In the smoke, the two fluids of which I have spoken are mixed; it would be easy to receive and apply their undivided action simultaneously: but since there are differences in their way of acting preferably, they should be received separately, and therefore it is suitable to indicate the means of doing so.

[0005] A very large part of the condensable vapours is released from the wood to the heat of boiling water, while it is only at a much higher temperature that permanent gases are formed. This observation reveals to us a way to obtain, as much as possible, the requested separation from their efforts. It is sufficient to expose the fuel, first in a kind of dryer, at a heat a little lower than that necessary for the formation of permanent gases. Thus, the furnace intended to operate the formation of gases will not be able to adsorb heat. It must afterwards be drained in the dryer to be used for the release of vapours. Now the shape of the dryer is not some kind of ordered, or at least indicated: it must have the same shape as the furnace, it must serve as a kind of envelope, and leave no space that separates it from it except that is necessary for the circulation of the current required for the consumption of coal in the furnace. This current will be directed between the two stoves in a zigzag pattern, so as to provide it with the opportunity to strip as much as possible in his caloric. Thus it will be possible to use separately or simultaneously the expansive force of the vapours and gases which are removed from the fuel during carbonization. After having highlighted these first two purposes of utility that my “thermolamps” offer (This is how many people like to name my device), I will try to point out a few others.

[0006] At the moment when the flammable air of thermolamps by ignition combines with atmospheric air, [the following products are formed]: Firstly, water by a combination of hydrogen and oxygen, as hydrogen is a gas that is inflammable by oxygen, a gas that is contained in atmospheric air. Secondly, carbonic acid by carbon [combining] with oxygen [???] . Thirdly, ammonia gas by combining hydrogen with nitrogen, a precious combination, solicited and by the affinity of these two principles, and by the presence of carbonic acid, which I have seen in similar circumstances, with the difference alone, that they were less favourable. It is observed above all that the proportion of the principles composing the flammable gas of thermolamps can vary approximately according to the operator [of the thermolampe]. Some of the steam from the bitumen and pyroligneous acid that emanates from the wood can even be entered there. Whatever the number and sets of these affinities and combinations is, it is always demonstrated, by experience, that the dilation in time of inflammation is prodigious; that it can overcome the most powerful resistances. What experience tells us about the strength of these detonations, reflection explains to us, that the water that is formed is in the form of steam. and that it is in a state of glowing, as well as the other gases that result from combustion. Therefore, the strength of each other must be extraordinary.

[0007] I will now indicate the means of collecting this expansive force, moderating its energy and deploying it only to the extent and proportion of the needs and the solidity of the machines that can be used. In cylinder a, Pl. 10e., fig. 2e., the combustion of the flammable gas, which is introduced by means of pipe b, while the atmospheric air necessary for combustion is returned to it by pipe c.

[0008] The cylinder receives the vapours produced by this combustion, its piston d intercepts any communication between the e and f parts. Box g contains four valves, their clearance, determined by a regulator under the command of the movement of the piston d, introduces steam, sometimes in the e part of cylinder h, while that contained in part f escapes through pipes i and j, and sometimes in part f, while that contained in the other part e escapes through pipe k and j.

[0009] The piston rod diverges outside the cylinder into three other rods and even a larger number, if necessary: one of them moves the piston l of a double-acting atmospheric air pump; another moves the piston m of a similar flammable gas pump; the third is intended to be applied to the resistance that is proposed to be overcome.

[0010] Now let's look at the effects of this device, and let's try to appreciate them by calculation. We will assume the movement begins, as well as the ignition of the gas, in cylinder a, and that in this moment, by the interaction of the valves of the box g, the gas contained in the part f of the cylinder has a free exit, and [the gas] produced by the ignition in the cylinder a has a free communication in the other part e of the same cylinder. It is obvious that the expansive force, produced by the ignition, will tend on one side by acting on the piston d, to carry it towards the part f, and on the other hand, reacting on the pistons l and m, whose surfaces together must be less than those of the piston d, to destroy part of this effect. Finally, the resistance to which the rod applies will not yet oppose this movement.

[0011] So let have the piston d a surface a,

a' [the surface] of the piston l,

a'' [the surface] of the piston m:

[then] a = 2 (a' + a'').

[0012] h, the height of the water column which could be supported by the expansive force of the gas, resulting from the combustion of flammable air in atmospheric air, after having spread into a space double that occupied by these two airs.

[0013] Finally, let us represent the sum of the resistances that we propose to overcome, by that which would offer to raise a column of water, whose base would equal a' + a'' = ? / ?, and whose height we are looking for would be h', we will obviously have the following equation:

[0014] h x a = h x a' + h x a'' + h x (a' + a'')

and substitute and reduce h = h', the height of this column of resistance forces would therefore be that of the water column which represents the expansive force produced by the detonation of the gases after they have spread in a space double that of which they occupied. Now the experiments on this force teach us that this height must be extraordinary higher than that which measures the force of our fire machines [i.e. steam engines], it will even have to be moderate; but it is enough for this to reduce (all other things remaining equal) the diameters of the cylinders l and m.

[0015] If the gases that result from this detonation are either condensable by cooling, or absorbable, then we can still add to this force the effect of vacuum, as in our ordinary fire machines.

[0016] We know that once the ignition of the gas by an electric spark has started, it can be maintained even in closed vessels. An electric machine, driven by the gas could be arranged so as to repeat the detonations in moments whose intermittency could be regulated and determined. Then we would have the advantage of being able, depending on the circumstances and needs, to obtain more or less violent or sudden effects, and perhaps to determine combinations and effects that would not take place without the presence of the electrical current.

[0017] I think it is good to observe that fuel provides only a very small part of the materials that give rise to this light, this heat, this expansive force, and that the surplus is drawn free of charge from atmospheric air.

[0018] The same device I have just described offers a no less useful use of another product of my thermolamps; the combustion of coal can offer another source of strength and movement. This other very powerful and very energetic machine differs from the previous one only by the removal of the pump m. I suppose that all the coal that should be consumed in the cylinder f in a given time could be introduce in one go. It could, however, be introduced successively; but this approach does not seem to me to be necessary.

[0019] Any other substance or mixture of substances, which, by combustion or combination, produces an expansion, must produce similar effects. Thus, the combustion of the flammable gas and that of the coal could be combined in cylinder f, even placing the whole and undecomposed fuel there. Sulfur, mixed with coal, would give effects close to those of gunpowder.

[0020] Note that the quantity of movement produced by these new fire machines does not deprive the other effects of heat, and that one can envelop the cylinders f and h by substances that one wants to subject to its action, or even reseize the caloric at the exit of the cylinders h. Finally, one must not fear that the resistance experienced by the expansive force can harm the combustion or even suffocate it. Suffocating means nothing other than depriving of atmospheric air, and the piston is intended to continuously discharge it, while through the interaction of the valves of the box g, the vapours or gases from combustion also escape continuously. This combustion therefore differs from that of our stoves, only in that it takes place under greater pressure, far from harming this operation.

[0021] I am not talking about the effects that could be achieved by still applying the heat produced to the boilers of our ordinary fire machines, nor about the countless applications of the force that is deployed in these new machines. All that is likely to be done mechanically in the object, and the simultaneity of so many precious effects making the expenditure proportionally very small, the possible number of economic applications becomes infinite in the forges. One neglects and loses all the flammable gas, which nevertheless offers effects of heat and movements so precious for these establishments. The quantity of fuel consumed, often far from forests and mines, whose deprivation gives rise, in droughts, to unemployment all the more harmful as they leave a large class of workers without work there, is so enormous that I am convinced that by reducing [the quantity of fuel consumed] considerably one could, following the views I indicate, not only obtain the same heat effects, but even overabundantly give the force that one borrows from the course of water. In general, all establishments that require movement, or heat, or light, must derive some benefit from this method of using fuel for these purposes.

[0022] However, since the greatest number of applications of thermolamps have as their object heating and lightening, I will consider them particularly from this point of view.

[0023] The shape of the vessels in which the fuel is subjected to the decomposing action of the caloric can vary infinitely, depending on the circumstances, needs and localities.

[0024] I shall confine myself to indicating a few provisions which seem to me to be interesting to know, and which, moreover, will give an idea of the multiplicity of forms of which these vases are susceptible.

[0025] The wood can be contained in a simple cylinder exposed to the heat of a furnace whose action applies in the same moment only to a part of this cylinder, but successively to each of them, by a movement of translation and rotation. It may be proposed to extend, by this provision, the duration of the release of the flammable gas, making it less abundant at the same time, and by attacking only part of the wood used.

[0026] This being said, it is obvious that as the carbonization takes place, the cylinder, becoming lighter, will be lifted by the float, and that the degree of carbonization will depend on the ratio that will be established between the weights and volumes of the cylinder and float.

[0027] It would also be possible to lower the furnace as the cylinder went up, and to establish between the speeds of one and the other the ratio that one would consider suitable. Finally, the vase that contains the wood could wrap the stove, instead of being wrapped in it. There is an infinity of other embodiments that would be too great to explain in detail, which are determined by the circumstances and needs determine, but which can easily be conceived.

[0028] It is often suitable to purify, or to charge, or to combine the flammable gas. Consequently, the inflammable gas is put in contact with cold surfaces, or when forced, under various degrees of pressure and temperature, the flammable gas may pass several times successively solid or liquid substances. In the latter case, it is useful to receive the gas, in the middle of these substances that it must pass through under inverted capsules, pierced with small holes. By this means, the gas is divided into globules, the surfaces are multiplied and the operation is facilitated.

[0029] The gas that produces the flame, well prepared and purified, will not comprise [any of the] inconvenient [constituents, such as] oil, or tallow, or wax [which are otherwise] used to illuminate us. However, since the appearance of an evil is sometimes as dangerous as the evil itself, it is not useless to point out how easy it is to spread in the apartments only light and heat, and to reject outside all other products, even that resulting from the combustion of this flammable gas. This is how I installed it in my home.

[0030] The combustion of the flammable gas is done in a crystal globe, supported by a tripod, sealed so as not to let anything escape outside the products of combustion. A small pipe brings flammable air there; a second pipe introduces atmospheric air, and a third pipe carries away the products of combustion. A small pipe brings flammable air there; a second pipe introduces atmospheric air, and a third pipe carries away the products of combustion. The one of these pipes that conducts atmospheric air, takes it inside the apartment when you want to renew it there, or otherwise it pulls it out. As these pipes unite below the globe, it is necessary that [the pipe] for the exhaust gas rises vertically in a part of its course. [It is further necessary] that [this pipe] be a little warmed up, at the beginning of the operation, to initiate the draft. Moreover, each of these pipes can have a tap or a valve, so that one can establish whatever relationship one desires between the gas supplies and the draft.

[0031] It is conceivable, without being necessary to explain it, that the globe can be suspended, and descend from a ceiling. In any case it is easy, by the arrangement of the pipes, to make the combination of the two principles of combustion prompt and immediate. [It is further conceivable] to distribute and shape the luminous surfaces, and to govern the operation as it sees fit. By this means, heat and light are given to us after having been filtered through glass or crystal, and they leave nothing to fear from the effects of vapours or metals [???]. It is not necessary, however, to absorb the products of combustion, which takes place in an exactly closed globe; a small dome or capsule of glass, crystal, porcelain or other material. [The products of combustion] can be collected to introduce them into a pipe, which, by its draft, would evacuate them continuously.

Reception of Lebons gas engine

Lebons idea of using distilled gas for illumination inside and outside a house was well received in other countries and was an inspiration for other entrepreneurs, as newspapers in France, Germany and other countries were reporting about his demonstrations in a house in Paris he had equipped with his "thermolamps". So his thermolamp survived him and in France he is known as the founder of the gas industry. Unfortunately his revolutionary idea of an internal combustion engine did not find the same resonance, probably because no prototype was ever built. His gas machine is shortly mentioned almost 100 years later in the 1898 book "GAS  AND  PETROLEUM ENGINES", translated and adapted from the French of HENRY DE GRAFFIGNY, edited by A. G. ELLIOTT, B.Sc., LONDON, WHITTAKER AND CO., 2 WHITE HART STREET, PATERNOSTER SQUARE. available in the Gutenberg project, chapter 1, 4th paragraph: 


Philip Lebon, of Brachay, the creator of the coal gas industry in France, took out a patent in 1799, setting forth very clearly the principle and construction of an engine using the explosion of coal gas as its motive power. Lebon, in fact, devised his gas-producing plant with the intention of only using the coal gas in his gas engine, lighting by its means being quite an afterthought. In a second patent two years afterwards he describes a more perfect apparatus, in which a pump is provided for compressing the mixture of coal gas air, and also an electric machine worked by the engine itself for igniting the compressed mixture. Unfortunately, the career of this fertile inventor came to an abrupt end by his assassination in 1804. It is highly probable, that if he had lived gas engines would have come into general use at the beginning of the century instead of nearly sixty years later.


In 1955 Philippe LeBon's official death certificate has been made available. There is no suggestion that he died of unnatural causes. He was known to have been in an ill health condition for a while. The story that he was mugged and stabbed 13 times with a knife seems to have been invented in a book for children about Technologies around 1870 [3]

Final thoughts about Lebon

Lebon's patent is the first description of an internal combustion engine for combustible gases with internal ignition. If he would have lived longer, would he have got his machine to work?  Would Lebon have been able to control the combustion speed such that it would not destroy his machine, a problem that Lenoir and Otto and probably many others were facing 60 years later? 

Lenoir, as we will see avoided too heavy explosions by igniting a non-compressed, i.e. weak combustion mixture when the piston had travelled almost half way in its cylinder. Otto increased the efficiency by compressing the combustible gas mixture in a separate stroke of his four-stroke engine, but controlled the combustion speed by admitting residual gases to dilute the oxygen that was sucked in. On the other hand wood gas probably was less "explosive" than coal gas. Maybe  Lebon would not have had the same problem. We might only know if Lebon's machine would have worked without destroying itself if someone would build a model of the Lebon gas machine, or at least runs a simulation.

Lebons great-great nephew, his first biographer, tries to glorify Lebon as if he had almost pre-empted the four stroke principle because Lebon compressed the air and the wood gas in separate cylinders before the mixture was allowed to access the working cylinder in which the mixture was ignited. In his patent specification Lebon broadly explains over several pages the advantages of combustible gases and variations of their usage, while he does not go into details about the compression pumps and their signification. I therefore believe that the pumps were merely intended to direct the gas streams into the mixture chamber. I believe Lebon had not perceived the idea that pre-compressed air and pre-compressed combustible gases would increase the efficiency of his machine. However, this is not an intention to dwarf his iventive spirit as Lebon was definitely ahead of his time with his idea of using distilled gases as a fuel for a expansion machine and ignite the combustible mixture in the working cylinder.


[1] M. Charles Gaudry, LA VIE ET L’ŒUVRE DE PHILIPPE LE BON in "L'industrie du gaz en France 1824-1924; Edité à l'occasion du Centenaire de l'Industrie du Gaz en France et du cinquentenaire de la société technique de l'industrie du gaz", Paris 1924.

[2] Jacques Quehen, L’industrie du gaz de ville en Normandie)