Couronne de tasses; plates 2 inches square;

surface $200

square inches.

Its effects.

Intensity of the electricity in

creases with the number, &

quantity with

the extent of the series.

experiments,

with an apparatus very different in size and number of plates from the one juft described.

This second battery was precisely the couronne des tasses of Sig. Volta, consisting of two hundred pairs of plates, each about two inches square, placed in half pint pots of common queen's ware, and made active by some of the liquor used in exciting the large battery, to which was added a fresh portion of sulphuric acid, equal to about a quarter of a pint to a gallon.

To state as shortly as possible the effects produced by this battery:

Experiment 1. It decomposed potash and barytes readily. Exp. 2. It produced the metallization of ammonia with great facility.

Exp. 3. It ignited charcoal vividly.

Exp. 4. It caused considerable divergence of the gold. leaves of the electrometer.

Exp. 5. It gave a vivid spark, after being in action three hours. At the expiration of twenty-four hours, it retained sufficient power to metallize ammonia, and continued, with gradually decreasing energy, to produce the same effect, till the end of forty hours, when it seemed nearly exhausted.

From the results of the foregoing experiments, which, though simple and not numerous, I trust, are satisfactory; we see Mr. Davy's theory of the mode of action of the voltaic battery confirmed: he says (in his Paper on some chemical agencies of electricity, sect. 9, after having shown the effect of induction to increase the electricity of the opposite plates) "the intensity, increases with the number, and the quantity with the extent of the series*"

This proved by That this is so, the effects produced on the platina and iron the preceding wires, in the first and fifth experiments with the large baton perfect con- tery, and the subsequent experiments on imperfect conducductors, tors with the small apparatus, sufficiently prove. The platina wire being a perfect conductor, and not liable to be oxidated, presents no obstacle to the free passage of the electricities through it, which, from the immense quantities given out from so large a surface, evolve, on their mutual an

Journal, vol. XIX, p. 55,

nihilation,

nihilation, heat sufficient to raise the temperature of the pla tina to the point of fusion.

With the iron wire, of th of an inch diameter, the ef- and imperfect fect is very different, which is explained by the low state of conductors. the intensity of the electricity) sufficiently proved by its not causing any divergence of the gold leaves of the elec trometer); which being opposed in its passage by the thin coat of oxide, formed on the iron wire, at the moment the circuit is completed, a very small portion only of it is transmitted through the wire. To the same want of intensity is to be attributed the total inability of the large battery to decompose the barytes, and its general weak action on bodies which are not perfect conductors. The small battery, on the contrary, exerts great power on imperfect conductors, decomposing them readily, although its whole surface is more than thirty times less than that of the great battery; but in point of number of plates, it consists of nearly ten times as many as the large one,

The long continued action of the small battery proves Importance of the utility of having the cells of sufficient capacity to hold having the cells sufficiently ca a large quantity of liquor, by which much trouble of emp- pacious, tying and filling the troughs is avoided, and the action kept up, without intermission, for a long space of time, a circumstance, in many experiments, of material consequence. Beside this advantage, with very large combinations, a cer-.and some distain distance between each pair of plates is absolutely neces- tance between sury, to prevent spontaneous discharges, which will other- plates. wise ensue, accompanied with vivid flashes of electric light, as I have experienced, with a battery of 1250 four-inch plates, on the new construction.

each pair of

ty of common

And here I beg leave to mention an experiment, which, Argument for though not directly in point, cannot be considered as foreign the dissimilarito the subject of this paper. It has been urged, as one and Voltaic proof of the nonidentity of the common electricity, and electricity done that given out by the Voltaic apparatus, that in the latter away. there is no striking distance. That objection, however, must cease. I took a small receiver, open at one end; through perforations in the opposite sides of which were placed two wires, with platina points, well polished: one was fixed by cement to the glass, the other was movable, by

means

·

means of a fine screw, through a collar of leathers, and the distance between the points was ascertained by a small micrometer attached. This receiver was inverted over well dried potash over mercury, and suffered to stand a couple of days, to deprive the air it contained, as thoroughly as possible, of moisture, The 1250 plates being excited precisely to the same degree as the great battery, mentioned in the beginning of this communication; and the little receiver Striking dis placed in the circuit, I ascertained its striking distance to tance '02 of an be of an inch. That I might be certain, that the air in inch, with 1250 plates. the apparatus had not become a conductor by increase of temperature, I repeated the experiment several times with fresh cool air, and always with the same result; but perhaps it will be objected, that the striking distance was so small, as not to afford a satisfactory refutation of the argument alluded to, when it is considered to how very great a distance, comparatively, the spark of the common electrical machine can pass through air. The answer to this is obvious: in might be increase the number of the plates, and the striking distance creased. will increase; for we see throughout, the intensity proportioned to the number, and it probably may be carried to such extent, as even to pass through a thicker plate of air, Another proof than the common spark. The great similarity of the appearance of the electric light of this battery in vacuo, and that of the common machine, might also be urged as an ad‐ ditional proof of the identity of their nature.

This distance

of their iden

tity.

Numerous combination

fused but little platina.

Effect of the

apparatus in the compound ratio of the

The effect of this large combination on imperfect conductors was, as may be supposed, very great; but of the same platina wire, of which the four-feet plates fused eighteen inches, this battery melted but half an inch, though, had the effect been in the ratio of their surfaces, it should have fused nearly fourteen inches.

The absolute effect of a Voltaic apparatus, therefore, seems to be in the compound ratio of the number, and size of the plates: the intensity of the electricity being as the number & size. former, the quantity given out as the latter; consequently regard must be had, in its construction, to the purposes for which it is designed. For experiments on perfect conductors, very large plates are to be preferred, a smail number of which will probably be sufficient; but where the resistance

of

}

of imperfect conductors is to be overcome, the combination must be great, but the size of the plates may be small; but if quantity and intensity be both required, then a large number of large plates will be necessary. For general pur- 4 inches square poses, four inches square will be found to be the most con- a convenient venient size.

size.

Of the two methods usually employed, that of having the Plates joined copper and zinc plates joined together only in one point, together in one point only preand movable, is much better than the old plan of soldering ferable. them together, through the whole surface, and cementing them into the troughs: as, by the new construction, the ap paratus can be more easily cleaned and repaired, and a double quantity of surface is obtained. For the partitions in Troughs of the troughs, glass seems the substance best adapted to se- Wedgwood's ware best. cure a perfect insulation; but the best of all, will be troughs made entirely of Wedgwood's ware, an idea, I believe, first suggested by Dr. Babington,

XI.

Report of a Memoir of Mr. HASSEN FRATZ, respecting the Alterations, that the Light of the Sun undergoes in traversing the Atmosphere. By Mr. HAUY*.

THE class of physical and mathematical sciences having directed Mr. Laplace and me to examine a paper of Mr. Hassenfratz on the changes that the solar light undergoes in passing through the atmosphere, we shall proceed to give

an account of it.

rays were not

The light of the sun being composed of an infinite uum- The sun would ber of rays of different tints, the union of which forms always appear white, we should always see it white, if it came to us in the white, if its state in which it is emitted from that body. But in passing affected in through the atmosphere it frequently undergoes alterations, passing thro that change its appearance, so that there are circumstances sphere. which it appears to us with its natural whiteness, and

* Journal de Physique, vol. LXVI, p. 356.

others

mine the kind

others in which it appears yellow, orange coloured, or red. According to Mr. Hassenfratz these different effects depend in general on the state of the atmosphere, the difference of the latitude, and the elevation above the sea. As to the ultimate cause of these phenomena, it was natural to ascribe them, as Mr. Hassenfratz does, to the suppression of a part of the rays of the solar light in its passage through the atmosphere. Newton has already aunounced this property of transparent mediums, to stop certain of the rays that enter them, letting the rest pass on; and this celebrated philosopher even remarks, that they are frequently absorbed one after another at different distances from the surface at which the light entered; and he quotes for example the various tints exhibited in succession by a coloured fluid in a conical glass, which is placed between the eye and the light, and raised so as to have the thickness traversed by the visual ray continually increasing.

Object of the Now Mr. Hassenfratz proposes to determine the number author to deter and kinds of rays, the suppression of which occasions the and quantity of various tints, that alter the primitive whiteness of the solar rays interceptlight. The means he has employed are founded on a rule ed. given by Newton, to determine the colour produced by a given mixture of rays of different kinds taken from those that compose the solar spectrum. It follows from this, that, if we can know the sorts of rays that the atmosphere takes away from the solar light, we shall know by necessary con sequence the colour produced by the mixture of the species remaining, and we may judge whether this colour be the same as that, under which the disk of the sun presents itself. Here we must observe, that the mixture producing a given colour may be more or less compounded, because a colour does not change, at least with regard to its species, by the addition of parts of the spectrum situate on each side at equal distances from the point considered as the centre of this colour. For instance, if we add to the green its two contiguous colours, blue and yellow, we still have green; and the mixture will remain green, if we farther add indigo and orange, one of which is contiguous to the blue and the other to the yellow. Nothing but direct experiment therefore can indicate the species of rays absorbed in their pas

sage,