termed its free state that it becomes evident to our instruments or senses. Among bodies water would seem to possess it in greatest quantity. Faraday and others have demonstrated, that there is as much electricity locked up in a grain of water as would cause an ordinary thunderstorm. The electricity contained in the water, apparently by the law of its composition, may, for convenience sake, be termed its latent electricity, and that which exists on aqueous surfaces, for the same reason, be termed specific electricity. When evaporation takes place at the surface of the water, being, as we have seen, a chemical change, the electrical equilibrium of this body is disturbed. According to experiments made by myself and others, this disturbance is of a decidedly negative character; but, as my object is more to account for the real or positive electricity that exists in the atmosphere, than to explain the phenomena attendant on the absence of it in the free state, usually termed negative electricity, I merely allude to the fact.

Let us now assume the evaporation as having taken place, and the elastic gaseous vapour diffused pretty equally throughout the atmosphere; but, for this diffusion, it does not require us to suppose that it possesses a superior levity to raise it, in the first instance, from the surface of the water, and then elevate it to the higher regions of the atmosphere. The currents of air that always agitate the water liberate the thin plates of the nascent substance from the surface.

We must now search for another law of nature to explain its diffusion, it being nearly alike over vast spaces.

Fortunately, in the present state of science, this is easily found. The "law of diffusion" that exists among all gaseous bodies, no matter what their specific gravity, first noticed by Dr. Dalton, and since investigated, in the most masterly manner, by Professor Graham, at once points out that the elastic gaseous vapour of water is governed by this law, in common with all other gaseous bodies. Were it to be governed by the laws of gravity, it would only be found in the higher regions of the atmosphere, it being 625-air being 1,000. This elastic vapour, then, fills the higher as it does the lower regions of the atmosphere.

Observation has shown us that the temperature of the atmosphere falls one degree of Fahrenheit for every hundred yards above the level of the sea, varying a little, more or less, with the climate and

season.

Dr. Dalton and Gay Lussac have shewn, that when the dew point is 80° Fahrenheit, and the barometer stands at thirty inches, the quantity of elastic vapour held in solution in atmospheric air is nearly the 48th of its whole weight and 1-30th of its bulk.

Let us pause for a moment, and review what is already said. First, evaporation is constantly taking place from the surface of the water, and when we take into consideration the immensely large proportion of aqueous superfices possessed by our planet, it will at once

point out the immense quantity of water that is daily abstracted from its surface. I have also said, that water, when taken up into the atmosphere by means of evaporation, is water no longer; but, by virtue of its combination with about 1,072 degrees of Fahrenheit of caloric, it becomes a gas possessing properties of its own, under certain circumstances possessing neither aqueous nor heating properties, just as we find in chemistry, that when an acid and an alkali combine they form a salt possessing totally distinct properties from either of their constituents. We have also seen, that, in accordance with the law of the diffusion of gaseous bodies, this substance must be pretty equally diffused throughout the atmosphere.

The experiments of Dalton and Gay Lussac prove this, and, indeed, those of all subsequent observers, to the average extent of 1-48th of its whole weight and 1-30th of its bulk.

These proportions are immense, and may show us the magnitude of the functions of this agent when mingled with the other gases of the atmosphere. I may here add, in parenthesis, that popular writers on physics, when speaking of the constitution of the atmosphere, will never convey correct notions on this subject, unless they enumerate aqueous vapour among the gases that constitute the air we breathe, it being of as much importance as any of the others, and, without it, it is difficult to see how any of the functions of animal or vegetable life could be performed.

It is true formula have been given by Mr. Daniels and others, by which we may calculate the amount of steam in the atmosphere, at certain barometrical pressures, combined with a given temperature, as thus, that the specific gravity of transparent aqueous vapour to atmospheric air is as 0.620 to 1.000. Suppose, then, we were to take 100 cubic inches of atmospheric out of a temperature of 60 Fahrenheit, and a barometrical pressure equal to 30 inches, we would find the whole to weigh 31 grains. But, suppose we wish to carry the inquiry still further, and find the actual amount of what is somewhat erroneously termed dry gas contained in the already given quantity of atmosphere, we should then find, that the 100 cubic inches had diminished in volume equal to 98.14; consequently, the transparent aqueous vapour, in such a quantity, would have a volume equal to 1.86 cubic inches. In like manner it would, also, be found, that the weight, 31 grains, had been reduced to 30.65, making the weight of 1.86 cubic inches of aqueous vapour equal to 0.35 grains. The term dry, applied to the other gases of the atmosphere, leads us to suppose, that the transparent aqueous vapour is really wet, when, in fact, such is not the case, as, before it will give out its water as such, a really chemical change must take place.

SECTION II.

Bearing in view the preliminary remarks on evaporation and the gaseous constitution of the atmosphere made in the former sec

tion, we shall now enter more immediately on the subject of the electrical phenomena of the atmosphere, together with the explanations of many others which arise necessarily out of the adoption of the theory I have to propound.

It is admitted on all hands that the air is always charged, to a greater or less degree, with transparent aqueous gas, or vapour.

It is also admitted, that a column of atmosphere moving upwards, will lose, by diminished pressure, 1° of Fahrenheit for every one hundred yards it ascends from the earth.

Whenever transparent vapour is formed at the surface, the law of diffusion will cause it to ascend, perhaps aided-but on this I do not insist-by its specific gravity, it being only five-eighths of that of the atmosphere. The circumstances of the locality will, in some degree, accelerate or retard.

Whenever this vapour ascends high enough in the atmosphere, it will be cooled down, according to a fixed law, until it forms cloud. The height at which this phenomenon takes place can be readily ascertained, at any given period, by the application of Dr. Dalton's great discovery of the dew-point; the height varying with the mean temperature and the amount of aqueous vapour contained in the air.

Whenever this change takes place, namely, the formation of cloud out of transparent aqueous gas, this body becomes decomposed, that is, its water, as such, is set at liberty, with about 1072° Fahrenheit of latent caloric, which was before insensible.

The caloric thus liberated expands the surrounding air enormously, and, from its levity, rushes upwards. This rush causes a corresponding movement in the outer circles of the atmosphere, and gives rise to one great section of meteorological phenomena, consisting of winds, storms, and tornados, well explained by Mr. Espy.

The water, which was before combined chemically in the gaseous state, is resolved into small globules of water, and forms what we term cloud. It is this cloud that furnishes materials for rain, hail, and snow.

When, however, this chemical change or decomposition of transparent aqueous vapour takes place, it is attended with another all-important, but hitherto unnoticed, phenomena, namely, the developement of a definite and necessary portion of electricity, whose force can be measured with as much accuracy as that of the latent caloric developed during the same phenomenon. It is the electricity developed during this change that causes thunder-storms, lightning of every description, violent storms of hail, water-spouts, and aurora borealis.

When the latent caloric is abstracted from the water, were it not for the electricity developed simultaneously, this water would be precipitated at once to the earth, in sheets or streams, or irregular spouts, or in fog or mists, according to the quality liberated; and

we never should have any permanent cloud floating in the atmosphere under any possible circumstances.

The electricity thus developed attaches itself to the small globules of water when liberated, and surrounds their surface, giving them more or less tension, according to the amount of aqueous vapour present in a given space when the change takes place.

The surface of all the globules of water composing a given cloud having a like amount of positive electricity, are repelled from each other by the well-known law of electrical repulsion between similarly electrified bodies: the consequence is, that the cloud remains permanent, and is floated off by the next current, as an immense Leyden jar possessing an enormous amount of free electricity.

A cloud, formed under the circumstances I have stated, and floated off amongst others into the atmosphere, may be said to possess its natural portion of electricity; that is, that portion which forms one of the necessary conditions of its being a cloud at all. Clouds formed under those circumstances comprehend the aggregate of all the clouds formed; and it would not be too much to say, that, in our variable climate, for one storm-cloud there are 10,000 formed that are not so.

In tropical climates, or in our own in summer, when the air is surcharged with aqueous gas by the immense evaporation that has taken place, and when there are no disturbing currents of any magnitude, a small cold current in the upper regions of the atmosphere will commence the process of cloud forming, which, under those circumstances, takes place with fearful rapidity, and, from the size of a dark speck, expands itself into an immense black canopy, darkening the face of the atmosphere, and it is only by some disturbing current that it comes in contact with on the other hand that the process stops.

Clouds formed under these latter circumstances, it is obvious, will possess a much greater portion of electricity than those I have previously adverted to, because they are formed in an atmosphere containing an extraordinary quantity of aqueous gas, and the air, from a comparatively large circle, rushes to the spot; when discharged of its gas, the whole of the electricity liberated is contained in such clouds. These clouds, then, are the true storm or thunder clouds, because they possess more than what I have already termed their natural portion of electricity.

Let us now take a cloud formed under the circumstances just detailed, and one or a series of those formed under ordinary circumstances. In the first place, it will be evident to all electricians, and, indeed, to those having the slightest knowledge of this force, that clouds formed under the different circumstances named will be positive and negative to each other; that is, the cloud formed under ordinary circumstances will be negative as respects the cloud just termed the storm-cloud, the one will possess more electricity than

the other. Let us now suppose, that the storm, or positive, cloud is floating in the atmosphere, and let it be borne in mind, that such clouds are generally higher or at greater distance from the surface of the land or water than the clouds formed under ordinary circumstances. This is said to arise from the air contained within the cloud being at a higher temperature than the surrounding atmosphere, and, in consequence of this rarefaction, their altitude is generally superior.

The storm-cloud is then carried by a current to the neighbourhood of a cloud that is negative with respect to itself. Whenever it comes within the sphere of its attraction, a discharge of the superabundant electricity takes place.

This discharge may take place under any of the following cir

cumstances :

First, the storm or thunder cloud may be a very large one, and, consequently, possess an immense quantity of free electrical force. If it comes in contact with a small negative cloud, a sharp clap of thunder, accompanied by a short shower of large dropped rain, will be the result, and the lightning given out will be by no means vivid. In summer, in our climate, such discharges often take place.

The small negative cloud that has just received the discharge from the large positive one now becomes in the same electrical state, and they roll off together. Both of the clouds now become positive with respect to ordinary clouds, but the larger positive one has diminished in bulk just in the ratio of the rain that has fallen, and a portion of the electricity of the cloud is carried to the earth or sea on the surface of the drops of rain. Thus agriculturists well know that a shower of rain will do more to hasten vegetation than nearly double the amount of water added to the soil by artificial This arises from the positive electricity, which, it is now well known, gives an immense impulse to vegetation.

means.

Should the two clouds that have now become positive come in contact with a series of negative clouds, sharp, rattling peals of thunder take place like the, discharge of artillery, seriatim, and forked lightning is the result, accompanied by tremendous showers of heavy, large dropped rain. In tropical climates, under such circumstances, from the quantity of water held in solution in the atmosphere, the water descends literally in sheets. This rain, or rather what is usually termed the thunder shower, will take the direction of the discharge of electricity; that is, supposing the storm-cloud to be situated due north, and the end of a series of negative clouds to be south as respects the positive one, then rain will begin north and end south. During the continuance of a storm of this description, should the electricity or lightning pass off into the earth, or be conducted into it by any prominent object thereon, then the air will suddenly brighten the dense black cloud will disappear, because it has been really annihilated, as a cloud, by the