one of chlorine are condensed into two volumes of this compound.

Exp. A particle of such a gas on the preceding principles, would as to the tenacious atoms, be represented by fig. 30; now the great force of the atoms of this particle will produce an abundant condensation of ethereal matter on their spherules, also the combination will be slender, partly on that account, and the decomposition will consequently agree with the effects of the explosion and expansion.

PH. 65. Oxygen and nitrogen gases put together in any proportions do not under common circumstances combine, but constitute a simple mixture.

Exp. This applies in most cases when the mixture consists of simple gases, and is agreeable to the theory and principles explained.

PH. 66. Oxygen and nitrogen may be made to combine in several proportions, the compound, containing the least proportion of oxygen, is constituted by weight of 16 oxygen and 28 nitrogen, or, in volume, one oxygen to two nitrogen, and the three volumes, when compounded, become two volumes of a gas called nitrous oxide.

Exp. From the phenomena connected with these substances, I conclude, that the spherule of nitrogen is greater than that of oxygen, fig. 29 may represent the combination, C and B being atoms of nitrogen, it differs from steam in the force of the atoms of nitrogen, and perhaps some little in the extent of its spherule. One volume is here condensed from the interior situation of the oxygen which is inclosed in the others.

PH. 67. A second compound of these elements, called deutoxide of nitrogen or nitrous gas, consists of equal volumes of oxygen and nitrogen, retaining the same volume in the combined state.

Exp. This may be represented by fig. 45, the small circle representing the spherule of oxygen: it is in some respects similar to the combination of chlorine and hydrogen ph. 54, and following, and may be conceived to be formed after the same manner. Hence, as in that case, there will be no condensation, but a difference of nature, in consequence of the difference in the absolute and relative forces of the atoms, and magnitudes of their spherules.

PH. 68. Another gaseous compound of these elements, called nitrous acid, is well known; it consists of two volumes of oxygen, and one of nitrogen, condensed into about one volume.

Exp. Under several circumstances, we may suppose such a compound formed, its elements being duly presented to each other; and taking as before the spherule of nitrogen to be nearly equal to that of hydrogen, fig. 46 will represent its particle as to the tenacious atoms, the number of atoms in simple gases being as the volumes, (prop. 25, sect. ii.): two atoms of the oxygen will be combined, with one of nitrogen, the action of the nitrogen will partly remove the ethereal matter from the interior surfaces of the oxygen, hence their spherules will attain their position at the center of the nitrogen, so that two volumes or nearly two will be condensed, the three volumes of gas becoming one or nearly one.

PH. 69. The nitrous acid (ph. 68) is slowly produced, by passing a succession of electric sparks through a mixture of oxygen and nitrogen; it is also obtained, with other products, by passing the electric spark through nitrous oxide (ph. 66), or nitrous gas (ph. 67).

Exp. That the almost instantaneous action of the electric spark on the mixed, or combined elements, which lie in the line of its rapid passage, should force many of the

atoms into a position similar to that of fig. 46, is a circumstance, which the theory would lead us to anticipate, and perhaps this is the most permanent of the simple compounds of these elements.

PH. 70. Hydrogen does not unite directly with nitrogen, when the two gases are simply mixed together; but when it is presented in a nascent state to nitrogen, it will unite with it forming a gaseous compound, such that two volumes contain one volume of nitrogen, and three of hydrogen, this compound is called ammonia.

Exp. Simple gases seldom unite by mere mixture (see ph. 59 and 65), but hydrogen, when immediately liberated from certain compounds, may combine with the adjacent atoms of nitrogen when such are present (see ph. 54), the relation of the spherules and forces may be such, that even three atoms of hydrogen shall unite with one of nitrogen, and be necessary to the support of the combination constituting an atom of ammonia.

A particle of this compound may be represented by fig. 47, the atmospherules of ethereal matter being supposed to be applied according to circumstances, and here n is to denote the nitrogen, h, h', h', the three atoms of hydrogen, the nitrogen is condensed from its internal situation, and, since the three centers are in the surface of the nitrogen, we may fairly suppose, that one third of the spherules of hydrogen are involved within it, and condensed, which will give the known contraction of volume.

PH. 71. Ammoniacal acid gas has a very strong pungent smell.

Exp. If the constitution of ammonia be as above explained, and represented in fig. 47, it is evident that the atoms of its hydrogen will, by means of very slight causes, oscillate on the central atom of nitrogen, and this will affect the atmospherules, several particles will be

occasionally decomposed, and the atoms of hydrogen, if not of nitrogen also, and perhaps even entire particles of ammonia, will be projected on all sides, and this will produce the smell and pungency of this gas.

PH. 72. Ammoniacal gas is decomposed by a succession of electrical sparks, it occupies a double volume when decomposed.

Exp. The electric spark, in its rapid motion, is sufficient to force the hydrogen to one side, and to separate some portion of it, in consequence of which the decomposition is effected. According to ph. 70, the volume of the decomposed gas ought to be double.

PH. 73. When ammonia is passed through red hot porcelain tubes it is decomposed,

Exp. A little attention to fig. 47, will shew, that, when exposed to a great heat, its elements will be easily separated; for the central atom being about 14 times stronger than the others, the caloric will be urged between every two adjacent sides of the hydrogen, and at a certain degree of intensity will necessarily effect their separation.

PH. 74. The volumes of gases, entering into combination, are generally in very simple and definite proportions, as one with one, or with two, or three, &c. this fact was first pointed out by M. Gay-Lussac.

Exp. In simple and in many compound gases, this will be the necessary consequence of the simple proportions in which the atoms combine, see ph. 29, 54, 62, and 70. For these phenomena and the theory will be sufficient to shew that, in simple gases, equal volumes will contain the same number of atoms; and in compound gases, the volume will contain either the same number of particles, or one half as many, or one third as many, &c. For according to the phenomena above referred to, the contractions will, in most cases, be none, two thirds, one

third, &c. the resulting volumes of the combination (ph. 53) being also generally in simple ratios, hence the combining volumes ought to be in very simple proportions.

PH. 75. When gases unite, the condensation is generally in some simple ratio to the original volume: but sometimes there is a considerable variation from this rule.

Exp. The reason of this was shewn, ph. 53, and will appear by the last phenomenon and the references there made, but that there may be instances of great differences will be seen by a consideration of ph. 60 and following.

Sch. The preceding examples may suffice to shew the application of the theory to the combinations of gaseous substances.

The explanations given are considered as being very probable, and, although they may not be absolutely the true ones, yet they will serve particularly to shew, that at least these phenomena are not opposed to our principles.

To estimate the relative magnitudes of atoms has, as yet, been found a problem too difficult to be solved, even in our present advanced state of knowledge. This however is a desideratum, it is a subject which many have investigated, and should these labours rest on a solid foundation, it is presumed that the way is a little opened towards the cultivation of this field of science, which presents the prospect of a rich produce, and an abundant harvest.

PH. 76. Many bodies require an elevated, or some particular temperature, in order to effect their combination: thus carbon and hydrogen, when made hot, readily combine with oxygen, but not so at the usual temperature.

Exp. When the temperature of a body is raised, the atmospherules of its particles are augmented, and greatly extended: hence in many cases the atoms of another body