accidentally made its way out into a servant's room, and lodged itself snug from notice into an old shoe. The alligator was not missed, but, upwards of twelve months after this, it was discovered about the house, full of life, and, apparently, scarcely grown bigger; one of his brothers, that had been kept in a tub and fed plentifully, had grown only a few inches during the same period.

Few animals emit a stronger odour than the alligator; and, when it has arrived at great size, you may easily discover one in the woods in passing fifty or sixty yards from it. This smell is highly musky, and so strong, that, when near, it becomes insufferable; but this I never experienced when the animal is in the water, although I have, whilst fishing, been so very close to them, as to throw the cork of my fishing line on their heads, to tease them. In those that I have killed, and, I assure you, I have killed a great many, if opened, to see the contents of the stomach, or take fresh fish out of them, I regularly have found round masses of a hard substance, resembling petrified wood. These masses appeared to be useful to the animal in the process of digestion, like those found in the craws of some species of birds. I have broken some of them with a hammer, and found them brittle, and as hard as stones, which they resemble outwardly also very much. And, as neither our lakes nor rivers, in the portion of the country I have hunted them in, afford even a pebble as large as a common egg, I have not been able to conceive how they are procured by the animals, if positively stones, or by what power wood can become stone in their stomachs.

Observations and Experiments on the Different Kinds of Coal. By M. KARSTEN.

THE

HE celebrated Chief of Mines in Prussia, KARSTEN, some time ago published, in his " Archiv für Bergbau und Hüttenwesen,” a valuable series of observations and experiments on the different kinds of coal met with in the mineral kingdom. This important treatise has been reprinted in a separate form, and sent to us. On reading it carefully, we feel convinced that a condensed view of its most important facts and inferences will be read with

interest by chemists, mineralogists, geologists, and, particularly, by all those who are concerned with coal mines. We shall arrange our view of this work under the following heads:

1. Preliminary Researches and General Considerations regarding Coal, and other combustibles.

2. Chemical Examination of Mineral Coal in general.

3. Application of the foregoing principles to the Coal-mines of England, France and Germany.

4. Observations on the Theory of the Formation of Coal.

1. Preliminary Researches and General Considerations regarding Coal and other Combustibles.

SOME naturalists have asserted, that coal constitutes a true rock formation, or original deposite, and therefore not deriving its origin from vegetables or any other organic matter. A more accurate knowledge of the nature of organic combinations, an advantage which we owe to the progress of chemical sciences, does not permit us any longer to consider coal as a combination of carbon with bitumen.

The transition of vegetable wood to the mineral which is called Bituminous Wood, or more properly Fossil Wood, is so manifest, that, in many cases, one might think he could determine with certainty the species of wood which gave rise to the existence of the mineral; but the more complete the alteration of the vegetable fibres has become, the less striking do the passages of the one substance into the other appear, and the more difficult to recognise. The fossil wood of Iceland, known under the name. of Surturbrand, has scarcely any resemblance to wood, at least in cabinet specimens. This substance appears to be a fibrous brown coal or lignite *; and frequently brown coal is distinguishable from true or black coal only, because it is surrounded by brown coal less complétely altered. By the denomination pitch-coal or jet, is sometimes designated a true coal, sometimes brown coal; and the columnar coal (stangenkohle) of Mount Meissner, in Hesse, is introduced into all the systems of mineralogy as a true or black coal, although it is nothing else than a brown coal altered by the action of basalt. Brown coal has no

* Vide Jameson's System of Mineralogy, and Manuel of Mineralogy.

where yet been found in a natural déposit of true or black coal, any more than true or black coal has been found in a deposite of brown coal.

The transition of black coal to glance coal or anthracite, is not less insensible than that of brown coal to black coal. True glance coal, as well as graphite, is a formation of rare occurrence; and, it would be difficult to point out any instances of their being associated with black coal. Yet this could never be a reason for rejecting, as improbable, the idea that glance coal and graphite may have arisen from the alteration of vegetable fibres, if there be nothing in the intimate nature of these bodies contrary to such an idea.

In unaltered vegetable fibres, the quantity of carbon is less, while the proportion of oxygen and hydrogen is greater, than in vegetable fibres that have undergone alteration. It is from a necessary consequence of this fact that the former, when put in contact with other bodies in a heated furnace, are so differently affected by them from the latter. The greater the alteration the fibres have experienced, the more apparent does the difference become; in other terms, this difference keeps pace with the increase of the relation which the quantity of carbon has to the quantity of the other constituent parts. In glance coal and graphite, this relation appears to have obtained its maximum ; and these two substances, or at least the latter, are regarded as a carbon entirely deprived of oxygen and hydrogen.

According to the ideas generally admitted, graphite is a carbon, and its difference of chemical character from carbon is explained by considering it as a chemical combination of ninety-five parts of carbon with five parts of iron, whence result 100 parts of graphite or percarburet of iron. As to the difference between glance coal and pure carbon, this is less obvious. It appears, in reality, that it is a difficult problem in chemistry, to explain the difference which exists between diamond, graphite, glance coal, and pure charcoal.

Peat, brown coal, and black coal, submitted to distillation in the dry way, almost always afford more or less distinct traces of ammonia. Such a result is not obtained from the distillation of unaltered vegetable fibre. Thus, azote appears to present itself as a new constituent part of altered vegetable fibre. However,

the proportion of azote is so small, in all the varieties of brown coal and black coal that have been submitted to examination by Mr Karsten, that this substance does not appear to be an essential constituent part of them.

Several brown coals and black coals yield an acid liquor by distillation; but most kinds of black coal furnish none. Peat, in the dry distillation, furnishes so great a quantity of acid water, that it is difficult to recognise clearly in that substance the ammoniacal basis which occurs in it, and this even on saturating the acid with potash.

Mr Karsten has carefully investigated and described the very different effects which are produced, whether on wood, and, in general, on unaltered vegetable fibre, or on altered vegetable fibres, on peat, brown coal, and black coal, by the different chemical re-agents, such as water, alcohol, sulphuric ether, caustic ammonia, hydrosulphuret of ammonia, nitric acid, and concentrated sulphuric acid. In his work we even find detailed accounts of the processes followed in these investigations. We shall confine ourselves, however, to the principal results. Those which are obtained on making the acids act upon vegetable fi bres, whether altered or recent, are perfectly in accordance with the manner in which acids comport themselves, and the circumstances of the body upon which they act. Nitric acid, which is easily decomposed, and, from this very circumstance, capable of oxidising, produces more promptly, and in a higher degree, the oxidation of vegetable fibres. This acid changes them into a substance analogous to tannin, or even into an acid, while sulphuric acid can only operate a conversion of the fibres into gum, and finally into sugar. Unaltered fibre undergoes its metamor phoses more quickly and more completely, because the greater proportion of the quantity of oxygen and hydrogen to the quantity of carbon facilitates the action of acids.

In proportion as the quantity of carbon increases, the chemical effect of acids becomes more and more feeble, and perfectly pure charcoal appears no longer susceptible of alteration from acids, excepting in a single case, which happens when this substance occurs, as it does in wood-charcoal, in a loose state of mechanical aggregation.

Glance coal, graphite and diamond resist the action of acids;

and this perhaps solely on account of their great density. Díamond, which is the densest kind of charcoal known, only burns at a very high temperature, and by means of pure oxygen. Glance coal and graphite are incomparably more easy to be destroyed; and the charcoal which is obtained on distilling black coal, brown coal, and unaltered vegetable fibres in the dry way, burns the more readily the looser the state of aggregation it assumes during the process of carbonization, or the less the quantity of carbon the body contains which has been employed for producing the charcoal. A coal that is carbonised in a furnace, or still better in a close vessel, affords a charcoal much more compact and more difficult to be burnt, than that which comes from the same coal carbonised in the open air.

gen

Elevation of temperature causes a decomposition of the combustible, and the formation of new combinations. This process has received the name of carbonization, because in this operation the residuum consists of pure charcoal. If hydrogen, oxyand carbon, on being subjected to different degrees of temperature, also obey different laws of combination, the quantity of pure charcoal which remains after the carbonization, must depend, not only upon the state of the body which is to be carbonised, but also upon the different degrees of temperature which have been employed during this operation. This is actually what takes places. Several resins and fats, which contain much more carbon than vegetable fibres, leave no trace of charcoal in their spontaneous decomposition at a high temperature; and in the same vegetable fibre, the quantity of charcoal residuum de pends entirely upon the degree of heat employed during the carbonization.

It is not the quantity of the carbonaceous residuum alone that must vary according to the different degrees of the temperature employed. The same cause must render more variable still the quantity and condition of the other combinations which are formed during distillation in the dry way, that is to say, during carbonization. This is the case precisely, because the quantity of the charcoal residuum is but a consequence of the nature and condition of the gaseous combinations and fluids, or vapours, which are formed during the operation. This difference in the manner in which organic combinations are affected under the