8. It has no action upon quicksilver.⚫

9. It combines with sulphur and phosphorus by heat, without any vividness of effect, and the compounds are highly inflammable,and emit ammonia, and the one phosphuretted and the other sulphuretted hydrogene gas, by the action of water.

As an inflammable gas alone, having the obvious properties of hydrogene is given off during the action of potassium upon ammonia, and as nothing but gases apparently the same as hydrogene and nitrogene, nearly in the proportions in which they exist in volatile alkali, are evolved during the exposure of the compound to the degree of heat which I have specified and as the residual substance produces ammonia with a little hydrogene by the action of water, it occurred to me that, on the principles of the antiphlogistic theory, it ought to be a compound of potassium, a little oxygene and nitrogene, or a combination of a suboxide of potassium and nitrogene; for the hydrogene disengaged in the operations of which it was the result, nearly equalled the whole quantity contained in the ammonia employed; and it was easy to explain the fact of the reproduction of the ammonia by water, on the supposition, that by combination with one portion of the oxygene of the water, the

oxide of potassium became potash, and by combination with another portion and its hydrogene, the ni trogene was converted into volatile alkali

With a view to ascertain this point, I made several experiments on various residuums, procured in the way that I have just stated, from the action of equal quantities of potassium on dry ammonia in platina trays, each portion of metal equalling six grains.

In the first trials, I endeavoured to ascertain the quantity of ammonia generated by the action of water upon a residuum, by heating it with muriate of lime or potash partially deprived of moisture; and after several trials, many of which failed, I succeeded in obtaining four cubical inches and a half of ammonia. In three other cases, where there was reason to suspect a small excess of water, the quantities of ammonia were three cubical inches and a half, three and eight tenths, and four and two tenths.

These experiments were per formed in the iron tube used for the former process; the tray was not withdrawn ; but the salt introduced in powder, and the apparatus exhausted as before, then filled with hydrogene, and then gently heated in a small portable forge.

Having ascertained what quan tity of ammonia was given off from the residuum, I endeavoured to discover what quantity of nitrogene it produced in combustion, and what quantity of oxygene it absorbed. The methods that I employed were by introducing the trays into vessels filled with oxygen gas over mercury. The product often inflamed spontaneously, and could always be made to burn by ■ slight degree of heat.

In the trial that I regard as the

most

most accurate, two cubical inches and a half of oxygene were absorb ed, and only a cubical inch and one tenth of nitrogene evolved.

Surprised at the smallness of the quantity of the nitrogene, I sought for ammonia in the products of these operations; but various trials convinced me that none was formed. I examined the solid substances produced, except nitrous acid; but the matter proveed to be dry potash, apparently pure, and not affording the slightest traces of acid.

-The quantity of nitrogene ex. isting in the ammonia, which this residuum would have produced by the action of water, supposing the volatile alkali decomposed by electricity, would have equalled at least two cubical inches and a quarter.

I heated the same proportions of residuum with the red oxide of mercury, and the red oxide of lead in vacuo, expecting that when oxygene was supplied in a gradual way, the result might be different from that of combustion; but in neither of these cases did the quantity of nitrogene exceed a cubical

inch and a half.

But on what could this loss of nitrogene depend; had it entered into any unknown form with oxygene, or did it not really exist in the residuum in the same quantity, as in the ammonia produced from

it ?

I hoped that an experiment of exposing the residuum to intense heat might enlighten the inquiry. I distilled one of the portions which bad been covered with naptha, in a tube of wrought platina made for the purpose. The tube had been exhausted and filled with hydrogene, and exhausted again, and was then connected with a pneu

It

matic mercurial apparatus. Heat was at first slowly applied till the naptha had been driven over. was then raised rapidly by an excellent forge. When the tube became cherry red, gas was devel oped; it continued to be generated for some minutes. When the tube had received the most intense heat that could be applied, the operation was stopped. The quantity of gas collected, making the proper corrections and reductions, would have been three cubical inches and a half at the mean temperature and pressure. Twelve measures of it were mixed with six of oxygene gas, the electrical spark was passed through the mixture; a strong inflammation took place, the diminution was to thres measures and a half, and the resi duum contained oxygene. This experiment was repeated upon different quantities with the same comparative results.

In examining the platina tube, which had a screw adapted to it at the lower extremity, by means of which it could be opened; the lower part was found to contain potash, which had all the properties of the pure alkali, and in the upper part there was a quantity of potassium. Water poured into the tube, produced a violent heat and inflammation; but no smell of ammonia.

This result was so unexpected and so extraordinary, that I at first supposed there was some source of error. I had calculated upon procuring nitrogene as the only aeriform product; I obtained an elastic fluid which gave much more diminution by detonation with oxygene, than that produced from ammonia by electricity.

I now made the experiment by heating the entire fusible substance, 02 from

from six grains of potassium which had absorbed twelve cubical inches of ammonia, in the iron tube, in the manner before described. The heat was gradually raised to whiteness, and the gas collected in two portions. The whole quantity generated, making the usual corrections for temperature and pressure, and the portion of hydrogene originally in the tube, and the residuum, would have been fourteen cubical inches and a half at the mean degree of the barometer and thermometer. Of these, nearly a cubical inch was ammonia and the remainder a gas, of which the portion destructible by detonation with oxygene, was to the indestructible portion, as 2.7 to 1.

The lower part of the tube, where the heat had been intense, was found surrounded with potash in a vitreous form; the upper part contained a considerable quantity of potassium.

In another similar experiment, made expressly for the purposes of ascertaining the quantity of potassium recovered, the same elastic products were evolved. The tube was suffered to cool, the stop cock being open in contact with mercury it was filled with mercury, and the mercury displaced by water; when two cubical inches and three quarters of hydrogene gas was generated, which proved that at least two grains and a half of potassium had been revived.

Now, if a calculation be made upon the products in these operations, considering them as nitrogene and hydrogene, and taking the common standard of temperature and pressure, it will be found, that by the decomposition of 11 cubical inches of ammonia equal to 2.05 grains, there is generated 3.6 subical inches of nitrogene equal te

1.06 grains, and 9.9 cubical inches of hydrogene, which added to that disengaged in the first operation equal to about 6.1 cubical inches, are together equal to 382 grains ; and the oxygene added to 3.5 grains of potassium would be .6 grains and the whole amount is 2.04 grains; and 2.05-2.04.01. But the same quantity of ammonia, decomposed by electricity, would have given 5 5 cubical inches of nitrogene equal to 1.6 grains, and only 14 cubical inches of hydrogene equal to .33, and allowing the separation of oxygene in this process in water, it cannot be esti mated at more than .11 or 12.

So that if the analysis of ammonia by electricity at all approaches towards accuracy; in the process just described, there is a considerable loss of nitrogene, and a production of oxygene and inflammable gas.

And in the action of water upon the residuum, in the experiment, page 52, there is an apparent generation of nitrogene.

How can these extraordinary re sults be explained?

The decomposition and composition of nitrogene seem proved, allowing the correctness of the data; and one of its elements ap pears to be oxygene; but what is its other elementary matter?

Is the gas that appears to possess the properties of hydrogene, a new species of inflammable seriform substance?

Or has nitrogene a metallic basis which alloys with the iron of platina ?

Or is water alike the aderable matter of nitrogene, hydrogene and oxygene?

Or is nitrogene a compound of hydrogene with a larger proportion of oxygene than exists in water?

These important questions, the

two

two first of which seem the least like ly to be answered in the affirmative, from the correspondence between the weight of the ammonia decom posed, and the products, supposing them to be known substances, I shall use every effort to solve by new labours, and I hope soon to be able to communicate the results of further experiments on the subject to the Society.

As the inquiry now stands, it is however sufficiently demonstrative, that the opinion which I had ventured to form respecting the decomposition of ammonia in this experiment is correct; and that MM. Gay Lussac's and Thenard's idea of the decomposition of the potassium, and their theory of its being compounded of hydrogene and potash, are unfounded.

For a considerable part of the potassium is recovered unaltered, and in the entire decomposition of the fusible substance, there is only a small excess of hydrogene above that existing in the ammonia acted upon.

The mere phenomena of the process likewise, if minutely examined, prove the same thing.

After the first slight efferve

scence, owing to the water absorbed by the potash formed upon the potassium during its exposure to the air, the operation proceeds with the greatest tranquillity. No elastic fluid is given off from the potassium; it often appears covered with the olive coloured substance, and if it were evolving hydrogene, this must pass through the fluid; buteven to the end of the operation, no such appearance occurs.

The crystallized and spongy substance, formed in the first part of the process, I am inclined to consider as a combination of ammonium and potassium, for it emits a smell of ammonia when exposed to air, and is considerably lighter than potassium.

I at first thought that a solid compound of hydrogene and potassium might be generated in the first part of this operation: but ex. periments on the immediate action of potassium and hydrogene did not favour this opinion. Potassium, as I ventured to conclude in the Bakerian lecture for 1807, is very soluble in hydrogene; but, under common circumstances, hydrogene does not seem to be absorbable by potassium."

Na former communication I

course of much subsequent experi

experiments, which induced me to conclude that the buds of trees invariably spring from their alburnum, to which they are always connected by central vessels of greater or less length; and in the

to change the opinion that I have there given. The object of the present communication is to shew, that the roots of trees are always generated by the vessels which pass from the cotyledons of the

seed,

seed, and from the leaves, through the leaf-stalks and the bark, and that they never, under any circumstances, spring immediately from the alburnum.

The organ, which naturalists have called the radicle in the seed, is generally supposed to be analogous to the root of the plant, and to become a perfect root during germination; and I do not know that this opinion has ever been controverted, though I believe that, when closely investigated, it will prove to be founded in error.

A root, in all cases with which I am acquainted, elongates only by new parts which are successively added to its apex or point, and never, like the stem or branch, by the extension of parts previously organized; and I have endeavoured to shew, in a former memoir, that owing to this difference in the mode of the growth of the root and lengthened plumule of germinating seeds, the one must ever be obedient in gravitation, and point towards the centre of the earth, whilst the other must take the opposite direction. But the radiole of ger minatiug seeds elongates by the extension of parts previously organized, and in a great number of cases, which must be familiar to every person's observation, raises the cotyledons out of the mould in which the seed is placed to vegetate. The mode of growth of the radicle is therefore similar to that of the substance which occupies the spaces between the buds near the point of the succulent annual shoot, and totally different from that of the proper root of the plant, which I conceive to come first into existence during the germination of the seed, and to spring from the point of what is called the radicle. At this period, neither the radicle

nor cotyledons contain any albur num; and therefore the first root cannot originate from that substance; but the cortical vessels are then filled with sap, and apparently in full action, and through these the sap appears to descend which gives existence to the true root.

When first emitted, the root consists only of a cellular substance, similar to that of the bark of other parts of the future tree, and within this the cortical vessels are subsequently generated in a circle, inclosing within it a small portion of the cellular substance, which forms the pith or medulla of the root.. The cortical vessels soon enter on their office of generating alburnous matter; and a transverse section of the root then shews the alburnum arranged in the form of wedges round the medulla, as it is subsequently deposited on the cen⚫ tral vessels of the succulent annual shoot, and on the surface of the alburnum of the stems and branches of older trees.

If a leaf-stalk be deeply wounded, a cellular substance, similar to that of the bark and young root is protruded from the upper lip of the wound, but never from the lower; and the leaf stalks of many plants possess the power of emitting roots, which power cannot have resided in alburnum, for the leaf-stalk does not contain any; but vessels, similar to those of the bark and radicle, abound in it, and apperently convey the returning sap; and from these vessels, or perhaps more properly from the fluid they convey, the roots emitted by the leaf-stalk derive their existence.

If a portion of the bark of a vine, or other tree, which readily emits roots, be taken off in a circle extending round its stem, so as to intercept entirely the passage of

any