Reverting to the experiment with a supersaturated solution of sulphate of soda, we see it is the air adherent to the glass rod which determines the act of crystallization, since if the rod is heated to 100° C. no such result follows. Is it then the air which suffices for this action or some peculiar quality contained in the air? The latter supposition seems the most probable since it is not caused by air which has been filtered through cotton contained in a tube, nor by air which has passed through a properly arranged series of flasks connected by tubes of glass. Air thus agitated or heated by friction, may be brought in contact with the supersaturated solution, under the form of a continued current, without determining the crystallization, which commences immediately in presence of normal air. Loewel attributes the modification produced by the air to the friction produced in his mode of experiment, and a recent experiment of Hirn proves that it is so.

The air thus rendered passive by Loewel is called adynamic air. Hirn has observed that the air is rendered completely adynamic when it escapes after compression in the form of a jet from the receiver in which it was confined. After this compression it can be directed with impunity into a solution of sulphate of soda saturated by heat in a closed vessel, On the contrary, the solution solidifies instantaneously if by the same tube, and without any derangement of the apparatus, some bubbles of ordinary air are allowed to pass into the solution. Here then, is an action purely mechanical which replaces the action of heat, a remarkable example of the correlation of force which raises a crowd of questions and which leads to the inquiry if an identical composition of the air should always have an identical action upon a living being; if air rendered adynamic by a storm is not found in different conditions in relation to organized beings than air long undisturbed.

This brings to mind that Schroeder and Busch have shown that fermentation is not caused by air filtered through cotton, and we now ask if the air rendered adynamic by the process of Hirn will not possess still more passivity.

It is an argument more in favor of this theory now held by the advocates of spontaneous generation to know that it is not by germs of infusoria suspended in the air that fermentation or putrefaction is carried These experiments appear to us to touch questions of the greatest importance in the sciences of observation, as well as others relating to the most interesting considerations in cosmogony,

.on.

Empiricism.-Application of the Physical Sciences to Medicine.-A discussion which has recently taken place in the Academy of Medicine on the action of iron used as a medicine has made known to us this unexpected fact that there are physicians who deny any influence exercised by medicines in virtue of their chemical properties, and who think that the physical and chemical actions of the animal economy differ entirely from those which are observed in the vegetable kingdom.

At the head of this retrograde school (which ignores the progress made by physics and chemistry in the last eighty years and to whom organized beings are composed of a material which is not subject to the general laws of matter which composes the universe) appears a physician celebrated more than the rest, Dr. Trousseau, who raising the banner of

vitalism has declared that chemical laws explain nothing when used in relation to man, and that medicinal agents act by unknown and very different means from those which chemists suppose. Space does not allow us to notice the reply made at the same sitting by another physician, Poggiale, who is also somewhat of a chemist. But we shall be asked what is the precise meaning of vitalism? Vitalism is a force in the category of what has been called catalytic force; this is a word which conceals our ignorance and which is evidently an obstacle to progress. This recalls that saying of Liebig, "If we allow forces to be created, investigations become useless and it will be impossible to arrivent the knowledge of truth." Vital force is then entirely for those physicians who ignore the first notions of physics or chemistry and think all has been said when they have installed this senseless word in place of an organic fact which ranks under the laws of mechanics, physics or chemistry. Vital force is insufficient to explain how it happens that a large number of substances, such as sugar, tartaric and malic acids, sulphur, sulphurets, salicine, &c., &c., undergo in the animal economy the same changes as when subjected to chemical action.

When we remember that slight compression of a muscle suffices to develop heat, and that its contraction evolves electricity, that in order to establish chemical action it suffices to place two heterogeneous bodies in contact-one is surprised that medical men should seek to explain the phenomena of life by "vital force"; as if the material of our bodies was exempted from the laws that regulate matter, as if what they call vital laws could interfere with the play of physical, mechanical, or chemical laws.

The discussion is not yet closed. It is still continued in the Medical Journals, some of which like M. Trousseau are vitalists in pathology and empirics in the domain of therapeutics.

Electro-Magnets and Magnetic Adhesion.*-We have on several occasions given in this Journal the progress of our researches upon magnetic adhesion, as well as the laws which regulate electro-magnets. At the request of several physicists and mechanics we have published the whole of our researches upon this subject, and a small octavo volume under the above title is the result. For the two electro-magnets, the rectilinear and the horse-shoe which were known in 1850, we must now substitute a larger number (several hundred) differing from each other by determinate properties. All these new electro-magnets which are described in this book, or whose existence has been foreseen, have at first rendered our task very difficult, for we were obliged to give names to them in order to facilitate their study. To give them such names as horse-shoe' only rendered their study more difficult, we therefore preferred to group them under a systematic nomenclature according to the principle of their natural classification.

We divide the electro-magnets into two great classes according to their form, these are:

1. Branched Electro-magnets.

2. Disk-shaped Electro-magnets.

* Les Electro-aimants et l'adhérence magnétique.

These classes are subdivided into families which rank according to the number of branches or disks of which they are composed; thus the rectilinear electro-magnet having only one branch will form the first family. The electro-magnet with two branches will serve as a type of the second family which will be that of bifurcated magnets, and the trifurcated electro-magnets or those with three branches form the third family; and finally the fourth family is composed of multifurcated electro-magnets, i. e., those with more than three branches. The families of electro-magnets stop here; there are consequently no quinto, sexto ... n furcated electro-magnets, experience having shown that the properties of electromagnets with more than three branches are very much the same, one new branch adding no new property.

The same method is followed with disk-shaped electro-magnets whose name is derived from dromos, course, in order to distinguish their most characteristic property, that of turning or revolving. These electromagnets are divided into two groups, viz:

1st. Para-circular. 2d. Circular.

The first group is subdivided into para-circular uni-dromes, bi-dromes, tri-dromes, or multi-dromes, according as they are composed of one, two, three or more disks, in the same manner as for the branched electromagnets.

Thus the three groups of electro-magnets are composed each of four families. These are subdivided into genera, determined by the number of helices; into species, characterized by the nature of the poles; and finally, into varieties, determined by the intensity of the latter.

The number of helices is expressed by the Greek words monos, di, tri,

knemes, from xvnuis-idos, (a greave or leggin,) the nature of the poles by the words isonomes or antinomes, and their intensity by the words isodynamic and heterodynamic. The use of these expressions requires some explanation, one fact heretofore unperceived in electro-magnets, one to which at least no importance has been attached, is that we use this apparatus without inquiring if the poles have the same or different intensities; and yet we have shown on several occasions:* 1st, that there is a great difference between electro-magnets of two categories and a difference no less great between bifurcated electro-magnets with poles of the same name or poles of different name. Take for example, the horseshoe, which has only one bobbin or spool, and which for that reason is called electro-aimant boiteux; it has two poles of unlike names, but these two poles are of different intensity; if we apply to this magnet the above nomenclature we shall have a bifurcate monokneme electro-magnet, with antinome and heterodynamic poles which consequently teaches us the properties of this apparatus just as the expression "sulphate of potash" tell us much more of the composition of that ternary than did the Sal polychrestum Glaseri of the alchemists.

If the question is in regard to the common horse-shoe magnet we shall say Bifurcated dikneme, for the circular magnets with three disks before described; then we shall call them tridome dikneme; that of the two disks we shall call bidome dikneme with isodynamic poles or with heterodynamic poles according as the helix is placed symmetrically or otherwise. * This Journal [2], xv, 107 and 383. † Vol. xvi, p. 110. Vol. xx, p. 101.

This very simple classification suggests the kindred simplicity of symbolical notation in chemical compounds. Space fails us to pursue this question farther, as well as many others agitated in this work in which the theoretical points particularly discussed are the following:

Of isodynamic and heterodynamic poles-Of anomalous poles (points conséquents) of magnetic phantoms-On the power of electro-magnets as affected by 1st, the elongation of the legs, 2d, the position of the helices, 3d, the distance between the poles-Of armatures-Of the form of polar surfaces-New process for measuring the effective power of electro-magnets-Of magnetic adhesion-Magnetization of locomotive wheels.

The latter process, which we have already described in this Journal (vol. xvi, [2], 337,) has since been successfully repeated in the United States, as we learn from a paper read by Mr. Blake at the Am. Sci. Assoc., 1859. This work is illustrated by five large plates. Nancy, Aug. 20, 1860.

SCIENTIFIC INTELLIGENCE.

I. CHEMISTRY AND PHYSICS.

1. Chemical Analysis by Observations of Spectra.-It is well known that many substances when introduced into a flame, possess the property of causing in the spectrum, certain bright lines. Bunsen and Kirchhoff have based upon these lines a method of qualitative analysis which materially extends the domain of chemical reactions, and leads to the solution of many difficult problems. In the present memoir, the authors develop the method for the metals of the alkalies and alkaline earths.

The lines in question become more distinct the higher the temperature and the less the specific illuminating power of the flame itself. Bunsen's gas lamp which gives a flame of very high temperature and very low illuminating power is therefore peculiarly adapted to these experiments.

The apparatus employed by the authors is sufficiently simple and does not require a large apartment for its successful use. It consists essentially of two telescopes and a hollow prism filled with bisulphid of carbon, and having a refracting angle of 60°. The eye-piece of one of the telescopes is removed and a metal plate substituted having a narrow slit which is placed in the focus of the objective lens. The lamp is placed. before this slit, so that the border of the flame lies in the axis of the telescope. The substance to be examined is placed in a little loop on the end of a fine platinum wire, and is supported in the flame, a little below the point where this is intersected by the axis of the telescope. The rays diverging from the slit are made by the objective to fall upon the prism, and after refraction are received upon the objective of the other telescope the magnifying power of which is about four. The slit should be so wide that only the most distinct of the dark lines in the spectrum are visible. The lower part of the prism carries a small mirror: a telescope directed towards this mirror permits the observation of the image of a horizontal scale placed at a short distance. By turning the prism, the whole spectrum of the flame may be made to pass by the vertical wire of the observing telescope, and every part of the spectrum to correspond with this

wire. A reading of the scale is to be made for each position of the spectrum; this reading however is not necessary for those who know the particular spectra by repeated observation.

Bunsen and Kirchhoff show in the first place, that the different states of combination of the metals examined, as well as very great differences of temperature in the flames produced, exert no influence on the position of the spectral lines corresponding to the particular metals. The same metallic compound gives a spectrum which is the more intense the higher the temperature of the flame; moreover, the most volatile compound of any particular metal always gives the greatest intensity of light.

When small pieces of potassium, sodium, lithium and calcium, are attached to the extremities of fine platinum wires enclosed in glass tubes and the spark of a Ruhmkorff's induction-apparatus is allowed to pass from one pole to the other-the spectra are found to contain the same bright lines as the flames. From this, it appears that these bright lines may be looked upon as certain indications of the presence of the metals in question. They serve as reactions by which these substances may be recognized more sharply, more quickly and in smaller quantities, than by any other analytical process.

The authors give in their memoir colored drawings of the spectra produced by the flames of the six alkaline and earthy metals, together with the pure solar spectrum for the sake of comparison: for these however, we must refer to the original memoir. The special results of the investigation, are as follows:

Sodium.-The spectral reactions of sodium are the most delicate of all. The yellow line Naa the only one found in the sodium spectrum corresponds to Fraunhöfer's line D, and is remarkable for its particularly sharp definition and its extraordinary brilliancy. If the temperature of the flame is very high, and the quantity of substance employed very large, traces of a continuous spectrum are observed in the neighborhood of the line. For this reason, faint lines in the spectra of other substances only become visible, in many cases, when the sodium reaction begins to fade away. The reaction is most distinct with the oxygen, chlorine, iodine, and bromine compounds, as well as with the sulphate and carbonate, but is also distinctly seen in the silicate and other non-volatile salts.

By volatilizing a known weight of soda in a room, the dimensions of which were known, and observing the effect produced upon a non-luminous flame, Bunsen and Kirchhoff have shown that the optical reaction is sufficiently delicate to detect less than the 3,000,000 of a milligramme of soda. It will easily be conceived from this that the atmosphere almost always gives a more or less distinct sodium reaction. The authors suggest that daily and long continued spectral observations may possibly show a connection between the presence and distribution of endemic diseases, and the quantity of sodium in the atmosphere, since chlorid of sodium is an antiseptic substance.

From the inconceivable delicacy of the sodium reaction, it will readily be understood that substances which have been in contact with the atmosphere even for a short time, rarely fail to produce the characteristic spectral line. Striking a dusty book for example produces at a distance of several steps the strongest sodium reaction.