is really in our power than we now suspect; and it is not quite unreasonable to hope that the entomological sagacity of a Latreille may hereafter perform for fossil entomology that which a few years ago would have appeared equally improbable in the history of extinct quadrupeds.

It is in the fresh-water formations chiefly that these researches ought to be made. A considerable number of the coleoptera inhabit the water or frequent it; and the bodies and wing-cases of these are of such durable materials, that we might expect to find them preserved in those deposits of mud, or sand, or calcareous matter which afterwards become the sandstones, shales, and limestones of these deposits. For analogous reasons, we might expect to find insects among the coal strata, since these also are of terrestrial or fresh-water origin; as we might further expect to discover them among the lignites. These are the produce of ancient forests and peat bogs; and there is no apparent reason why some of the more durable insects might not, as well as the tender shells, be found in such situations. But nothing will be found unless it is sought for.

I have taken it for granted, throughout this paper, that the vegetable origin of amber is admitted; improperly, perhaps, and for that reason, it will not be irrelevant to add a few words on the nature of the evidence on which this opinion

rests.

The existence of such animal remains in any undisputed specimens of amber, ought in itself to be a sufficient proof of this origin for the whole. It is impossible to conceive that winged insects could be entangled in any substance of this nature under any other circumstances; while 'their actual existence in resins now exuding from living vegetables, serves to explain the mode in which this otherwise inexplicable event must have occurred.

The chemical connexion between amber and the existing resins, must also be proved, if that be thought necessary for strengthening this view, by such analogies as can be brought to bear on it, since it is no matter for direct experiment.

In analyzing chemically the vegetable resins which most resemble amber in their general character, and in comparing these results with those obtained from the analysis of amber, certain important differences are observed. To enter into the whole of these would exceed the bounds I have here prescribed for this paper. It is sufficient to say, that the essential or volatile oils, obtained from all the resinous substances, possess a general resemblance to that obtained from

common rosin, or to the oil of turpentine; and that they exhibit the same chemical qualities as these relate, in particular very conspicuously, to their habitudes with alcohol and ether, and especially with naphtha, and to the action which they exert on the solid resins and on the solid bitumens.

The same general powers and properties are found in those essential oils which are produced by the decomposition of recent vegetables and the recombination of some of their elements; and thus a general character is found to pervade all those volatile oils which are the produce of recent vegetable matter under whatever form. But in analyzing in the same manner and reproducing volatile oils from vegetable remains, which have been so long and so deeply buried in certain alluvial soils as to lead us to suppose that they have belonged to a pre-existent state of the surface of the earth, it is found that these are essentially different. The volatile oils thus produced, approach in their affinities towards those which are obtained from coal; or from a substance, of which the vegetable origin is rather generally admitted than demonstrably proved. They are all varieties of naphtha, under modifications which, having fully explained them in other writings, it is not necessary here to detail again.

Now the same analogy holds in comparing the produce of the vegetable resins with that of amber, as occurs in comparing the oil of recent wood with that of jet, and more particularly with that of coal. It is here unnecessary to enter into the minute differences in these cases. The oil of amber, in all its most important characters, resembles naphtha; and thus it might, à priori, be suspected, that the same influence which could render wood in the form of jet (or coal), capable of yielding naphtha, might, under analogous circumstances, so change a vegetable resin as to cause it also to yield a species of naphtha instead of the resinous essential oil. This probability, of the change of vegetable resin into amber by long submersion in alluvial soils, is strengthened by other analagous occurrences.

In the submerged wood (brown coal of Bovey), a substance is found so intermediate in its chemical characters between vegetable resin and asphaltum, that Mr Hatchett has given it the very expressive name of retinasphaltum. It appears to be a vegetable resin, in which the change to amber, or to some analogous substance, is as yet so far incomplete, that it retains the mixed character of both. The same, or a similar substance has been found in other alluvial soils, as, for example, in the London clay (of Highgate :) and my analysis

proves this to be of the same chemical nature. In these instances, the incomplete change from resin to amber, or to a substance, at least, of which the distilled volatile produce would resemble naphtha, or the mineral essential oil, holds an exact parallel to certain of the cases in which the progress from brown coal, in the common vegetable fibre partially bituminized, can be traced down to perfect coal, or to a substance capable of yielding naphtha only on distillation.

It is from these analogies that we may perhaps safely conclude, that amber has been a vegetable resin converted to its present state during the same time, and by the same causes which have converted common vegetable matter into jet, and perhaps ultimately into coal.

That it is found in the same alluvial soils with jet, is perhaps too feeble an argument to deserve any weight; but it is also one which seems superfluous. Every circumstance which attends amber strongly bespeaks its vegetable origin; and nothing proves it more strikingly than that which forms the main object of this communication.

ART. IX.-On different Alloys of Potassium, and on the Inflammation of Gunpowder under Water. By M. SERULLAS. [From the Annales de Chimie et de Physique.]

GUNPOWDER may be fired under water by means of an exploding mixture of charcoal with an alloy of antimony and potassium, which takes fire on the first contact with water, and will instantly communicate it to the powder. This mixture is thus prepared: mix by careful rubbing 100 grammes of tartar-emetic with 3 grammes of lamp-black or common charcoal. Select crucibles holding 75 to 80 grammes, which must not be more than three quarters filled, make the upper edge smooth, and rub the whole inside with charcoal powder, that the charred mixture, when prepared, may not adhere to its sides. Put some of the materials into the crucible, cover it with charcoal powder, lute on the cover, and close every opening. Heat it for three hours in a good reverberatory furnace, then set it by for six hours to cool. This time is required to allow the air, which always penetrates more or less into the crucible, to burn the exterior layer of the fulmi

nating mass, for it is withdrawn too soon, if it always takes fire spontaneously. Then without loss of time enclose the calcined mass, without breaking it up, in a wide-mouthed vessel, where it gradually splits into fragments of different size, and in this state will preserve its properties for years.

When the calcination has been well performed, the product is extremely fulminating, so as to detonate with a report like fire-arms, by the first contact of water, and without requiring any compression. Instead of tartar-emetic and lamp-black, the following mixture may be used: carbonize cream of tartar by roasting it in an open crucible till it has lost about half its weight; takes 75 parts of this charred tartar, 100 parts of regulus of antimony, and 12 of lamp-black, and mix the whole by constant rubbing. Then calcine it in the crucible in the way above described.

With this fulminating substance it is easy to fire gunpowder under water. The experiment was made in the following manner: half an ounce of gunpowder was put into a strong glass tube closed at one end, of which the powder filled about one quarter. A piece of the fulminating alloy of the size of a pea, was laid upon the powder. The tube was immediately closed with a cork, which had been previously perforated with a small hole, stopped for the present with a little fat lute, soft enough to be readily pierced with a sharp pin when required. The tube thus prepared, was then sunk in a large vessel of water two or three feet deep, and was confined by weights to the bottom. Then the lute stopping the perforation of the cork was pierced with a steel wire fixed to the end of a long stick, and the moment that the water entered the tube the powder exploded, breaking the tube, and throwing out a four pound weight which had fixed it down.

The author then proceeds to describe several triple alloys of potassium and sodium with antimony and other metals.

Triple alloy of potassium, copper, and antimony.-This is prepared by melting together equal parts of carbonized tartar (already described) regulus of antimony, and copper filings. First rub together the carbonized tartar and antimony; put it into a crucible, cover it with the copper filings, previously mixed with a sixth part of antimony to promote its fusion, lute on the cover, and heat the whole for two hours in a furnace that draws well. This alloy, like that of antimony and copper alone, has a violet tint. It will divide into very thin brilliant plates, which flatten a little under the hammer. It is volatile in the fire. Pieces of it thrown upon mercury, covered with a little water, turn round rapidly.

Alloy of potassium, silver, and antimony.This is prepared like the preceding alloy: it is more volatile; its colour is a steel grey, and it has much lustre. It is very brittle, and contains much potassium.

Alloy of potassium, iron, and antimony.-Put at the bottom of a crucible some iron turnings, broken to small fragments, cover it with equal part of carbonized tartar and antimony, previously mixed, melt with a very strong heat, and you will have a triple alloy, containing much potassium and very brittle. A triple alloy with bismuth may be prepared in a

similar manner.

Alloy of potassium and bismuth.—Rub together 60 grammes of carbonized tartar, 120 of bismuth, and one of nitre, inclose the mixture in a crucible, covered with lamp-black, close it carefully, and heat it for two hours.

This alloy is very rich in potassium. The smallest fragment gives sparkles when cut with shears. As soon as it is broken, it melts and burns, leaving a residue of a greenish oxyde.

If the above alloy is made with 10 or 12 grammes of lampblack or charcoal instead of the nitre, a pyrophorus is obtained, which takes fire by the contact of water, and bursts with small explosions. It may be used for kindling gunpowder under water.

An alloy of potassium and tin is made in the same manner as the preceding, with 100 parts of oxyde of tin, 60 of carbonized tartar, and 10 of lamp-black. A double dose of lampblack gives a pyrophorus.

An alloy of potassium and lead is produced by 100 grammes of protoxyde of lead, and 60 of carbonized tartar, and an addition of 5 to 6 grammes of lamp-black gives a pyrophorus. M. Serullas remarks in the preparation of these different alloys, that the stratum of charcoal put over them to protect them from the action of the air, though in no way mixed with them, acquires the property of spontaneous inflammation in the air. This he can only attribute to the presence of potassium volatilized during the fusion, and retained by the charcoal. To pursue further the subject of the separation of potassium from its alloys by heat, the following experiment was made. A gun-barrel was cut nearly in halves, the longer end, which was closed by the breech at one extremity, was filled with a mixture of 50 grammes of carbonized tartar, 70 of litharge, and 2 of lamp-black. The barrel was curved slightly at the open extremity, to which was attached the recipient of GayLussac and Thenard for the preparation of potassium. The barrel was then thrust perpendicularly into a furnace up to