state, when the 1072° of caloric of elasticity is liberated, the same phenomena must attend the formation of the drops of rain into the pieces of ice, termed hail, that attends it in the former instance; or, in other words, the electricity must be given out simultaneously with the caloric of fluidity; but, it must be borne in mind, in less degree than when the caloric of electricity is developed.

This fully accounts for the flashes of lightning that accompany hail and storms. The lightning, as previously indicated, is harmless, comparatively, and necessarily so from the small quantity given out. The fact of it being diffused through an immense space also renders it of exceedingly low tension.

When speaking of this and other atmospheric phenomena, especially those related to or accompanied with electricity, an inhabitant of our own climate is somewhat prone to imagine that the meteorologist exaggerates the importance of these appearances. He at the same time finds it difficult to give credence to what he hears related of their effects; inasmuch as he is unacquainted with any, or but rare and mild examples in his own climate.

This may apply not inaptly to the lightning and intense violence of hailstorms; but an inhabitant of a mountainous district in south or central Europe has no such difficulties, as he witnesses them but too often during the summer and autumn.

Connected with this subject, it may not be uninteresting to show how practice has preceded theoretical discovery.

In the south of France and in parts of Switzerland, it is not unusual for proprietors of vineyards to elevate rods of wire to a height of from twenty to thirty feet in different parts of the grounds. These are termed paragrêles, and are erected with a view to protect the crops from those sudden showers of hail and pieces of ice that occasionally destroy the vintage of whole seasons. I am informed they are attended with the best effects, and if so the rationale of their use must be as follows :-Primarily the storm cloud that settles or forms over the vineyard descends in fertilizing rain, which, without the precautionary paragreles, would have discharged itself in hail, breaking down and destroying the fragile vegetation.

The reason of this appears to be obvious. The elevated rods discharging the cloud of a portion of its electricity, the water is, in consequence, precipitated in the form of rain; but, were this discharge of electricity not to take place at this period, the repellant globules would be carried perpendicularly up by the current caused by the formation of the storm clouds until they come to a cooler region of the atmosphere, there to be condensed into hail, where they would be thrown sharply off at the annalus of the upheaving current, accompanied by a flash of lightning, and, according to the circumstances of the next cloud, thunder. The hail would now be precipitated from a great height to the earth, and, from its force, would destroy the tender and fragile vegetation.

In these instances, the flash of lightning is given off from the

necessary decrease of surface that takes place when the small drops of water are condensed into the large drops that form the hail. So much is this method of producing rain instead of hail appreciated in those countries, it is stated, that, in the sandy arid plains of the south of France, the French Academy have instructed the proprietors of these districts to elevate rods of wire, at intervals, with the expressed object of attracting the clouds to discharge their rain; and, if the principles I have laid down are correct, it will, most likely, be attended with the desired effect.

It often happens, however, that hail falls in pieces of ice of immense magnitude, as if sheets of this substance were suddenly discharged and broken into pieces. This phenomenon is caused by the sudden abstraction of the electricity surrounding the globules of water, in its passage upwards, before it arrives at a temperature less than 32° Fahrenheit. The consequence of this is, that the globules condense into sheets or streams of water, which, in that state, are still borne upwards, and thrown off at the annulus of the upheaving current, where, meeting with colder air, they are suddenly frozen, and are precipitated to the earth in irregular masses. A hailstorm of this description is preceded invariably with thunder and lightning, and it is difficult to see how it could be otherwise.

We now arrive at the cause of the whiteness of snow, hail, and atmospheric ice, as distinguished from the general colour of ice frozen on the surface of water.

First, snow is cloud frozen at a high comparative altitude, each respective globule of which possessing its atmosphere of free electricity. These globules, while in the state of water, in all probability do not possess those beautiful arrangements that snow is found to possess, when viewed under the microscope, nor can they be so far apart.

The crystalline or radiant form proceed from the secondary electricity given out, as we have seen, during congelation. That this must be slowly and gradually developed, we may gather from the regularity of the forms. We have familiar instances of this in the laboratory, as we observe during the aggregation of crystalline masses on which free electricity is brought to bear: should there be a large quantity of electricity present, the forms will assume a friable, irregular appearance; but where it is slowly developed, and of feeble tension, the form of the body is the more compact and regular.

But, on the other hand, with hail, the drops of rain are already formed, and carried up with the current, where they become suddenly frozen as they are. Electricity is, in this, as in the other instance, given out, and prevents the particles of nascent ice from aggregating themselves as closely as if the same phenomenon took place on the surface of water, because the moment it was set at liberty it would be conducted away; but in the upper regions of the atmosphere there is no such conducting substance in contact with it.

The pieces of ice that descend are white from the same reason. We have a familiar instance of this on the earth's surface. We often observe white ice and black ice; but it is worthy of remark, that where the white ice is seen there is generally no water underneath, it having all been frozen, consequently there was no ready conductor, and the congelation took place in conjunction with a portion of the electricity that was liberated. On the other hand, in deep water, we see black, dense ice, because the electricity liberated is quickly carried off by the fluid water.

Having thus run cursorily over the most prominent parts of the views I have to propound on meteorological electricity and the attendant phenomena, I shall now briefly adduce the grounds on which my opinions have been formed.

Most chemical observers are agreed in opinion, that all chemical change is attended with a development of heat and electricity. Indeed, so much has this been observed, of late years, by the experiments of Faraday having called attention to it, that it may fairly be said to be an admitted law of nature.

I am a firm believer in such a law, because I find it coincident with all the experiments I have made, even should I have paid no credence to those made by others, which I am very far from doing. I have applied the knowledge of this fact to the solution of some meteorological phenomena.

First, then, I have viewed the transparent aqueous vapour that in all cases pervades the atmosphere as a gas. As this has been disputed, I may briefly state my reasons for adopting this view. When we classify bodies, whether compound or elementary, the segregation is made, in accordance with the properties they may possess in common, as the elements we term metals, generically, from platinum down to potassium, have certain properties in common: although, looking at these substances by themselves, scarcely two bodies in nature can be more dissimilar, yet we agree, and properly so, to term them metals. In like manner, then, with respect to the substance we term steam, when locked up in the boiler of the engine, and transparent aqueous vapour, when the same substance is in an invisible state in the atmosphere, I think I am correct in classing it under the head of a gas, for the simple reason, that it, too, possesses properties in common with gaseous bodies. Let us now see what these properties are. It is highly elastic: so are gases. It has a low, specific gravity: so have the gases; even lower than some gaseous bodies. It floats in an invisible state in the atmosphere: so do all the gas of which we already admit the atmosphere to be composed. It obeys a peculiar law which we already know all gases do, the law of gaseous diffusion. Need I say more? I may add, that most of the continental chemists I am acquainted with view it in the same light, and some in our own country. Nay, the matter appears so obvious that it seems a work of supererogation to say more on this head.

This gas, then, is a compound; but, so far as we know, all the gases are not compounds. Some of them we term simple or elementary; still, we have compound gases, as carbonic acid gas, and many others. This body, then, we must look on as such a gas, namely, a compound gas, made up of water and caloric, to say nothing of electricity; and, like the compound gases I have named, the combination is a chemical one. Let us trace the analogy that exists between it and carbonic acid gas. Carbon is united with oxygen to form this body: both of which, singly, play a distinguished part in the phenomenon of combustion; yet, when combined into one body, it would be difficult to name anything in nature to which it is a greater enemy. This resultant property, we say arises from the bodies having entered into combination chemically, because the opaque black body carbon, is transparent; and the same eminent supporter of combustion, oxygen, will put out a candle; and this is the correct way of viewing it.

We now come to the aqueous gas, steam, composed, as far as we know, of water and caloric. Water, one of the most elastic or incompressible of bodies, having a specific gravity more than some metals, and which binds it to the earth, yet, when it combines with a definite (mark, like all other chemical compounds) amount of caloric, it at once, as if by magic, loses these properties and assumes new ones. From being one of the most unelastic of bodies, it becomes, perhaps, the most elastic. From a heavy body it becomes, as we have seen, really lighter than the air we breathe, in the ratio of 640 to 1000, and mounts high into the upper regions of the atmosphere. While water, it moistened all bodies it came into contact with; but it even loses that property, and in time of drought, the air is surcharged with it to an incredible degree. On the other hand, the caloric contained in the same body, is so combined with it as to be perfectly insensible; that is, it will heat no body that it comes into contact with, although it contains, in reality, as much, or, indeed, more heat, than would render iron visibly red hot during the light of day.

I might reasonably pause here and ask, need I adduce further proof of a strictly chemical change having taken place?

Now, as no human eye has ever observed, nor, in all probability, ever will observe, chemical action, properly speaking, take place, it may be asked how we know that it has taken place at all? I answer, that it is known to take place simply by the effects produced those effects are known, as I have often repeated, when the bodies, entering into simple combination form a third, having properties totally distinct from either. Could I, then, have adduced an instance within the whole range of natural substances that more completely answers all the conditions of chemical change than the production of aqueous gas from the two bodies, water and caloric? I, without hesitation, answer no. But here, after all, is the stumbling-block with many who cannot imagine by possibility that

caloric has an entity, or rather is a body. If they could be made to comprehend this, then the difficulty ceases. As for myself, I firmly believe it to be a body. I can comprehend it, and, if asked how I know this, I answer, by its effects, just as I have already stated we know when a chemical change has taken place by the effects merely. Those who, at first, pronounced the air we breathe to be a body possessing substance were considered visionary, although we now know that the whole of the gases contained in it combine with other substances to form really solid bodies.

I have assumed, then, and I am not alone in the assumption, that when the change takes place that liberates the two bodies, water and caloric, it is strictly a chemical one, and, as such, obeys all the conditions we know are attendant on such changes. One of these is,

that a definite amount of electricity is given out.

The electricity when thus set free, not having the tendency to expand or rarefy the air, that the caloric has that is liberated at the same time, immediately attaches itself to the next conducting surface, which being the globules of nascent water, each globule then becomes surrounded with an atmosphere of electricity. The attraction between these two bodies prevents the water from falling to the earth, which it inevitably would, were it deprived of the electricity. Globules of water, then, and a portion of free or positive electricity, constitute the body that floats in our atmosphere termed cloud; but deprive it of the latter, and as cloud, it is annihilated, as the water will at once descend to the earth.

Here, then, is the pivot on which the whole of the observations I have made on the subject of atmospheric electricity turns. The whole of the arguments I have adduced have been built on this one fact. Take it away, and the totality of the structure I have endeavoured to rear it on, however elaborate or ingeniously contrived, or however plausible the details may be, at once tumbles to the earthas it ought.

But if, on the other hand, it does appear, by the test of all subsequent experiment and observation, that I am borne out in this view of the necessary nature of cloud, I then contend that the explanations I have endeavoured to make known are the just, I would say inevitable, deductions that arise out of a knowledge of this law of nature. NOTE. A fifth section will be devoted, to explain several of the facts on which these observations have been founded.

Meteorology. Observations on Shooting Stars, made at Paris, by M. E. BOUVARD, from October 1840 to October 1841.*

During a period of twenty years, many skilful philosophers have made observations on shooting stars, which have conducted

Comptes Rendu, No. 22, Nov., 1841.