ART. XIII.-Correspondence of Prof. JEROME NICKLÈS, dated Nancy, October 2d, 1866.

Obituary: Hermann Goldschmidt, the Astronomer.-The subject of this notice attained to a considerable reputation as an artist, but he is better known to the scientific world, in which he held a high position, by his numerous discoveries among the heavenly bodies.

He was born June 17th, 1802, but during his whole life his health was delicate. Destined at first to commerce, he quitted it to devote himself to painting, and early became distinguished in that career. He was, however, ignorant of his true vocation until he had attained the age of forty-five years. One of his friends, Dr. Hoefer, to whom we are indebted for these details, tells us the circumstances under which he became an astronomer. The recital is copied from Goldschmidt himself. "I had just returned," says he, "full of disgust from a very long sojourn in England. I tried in innumerable ways to dissipate my melancholy humor, but without success, when one day I chanced to attend LeVerrier's lecture on astronomy. The professor explained an eclipse of the moon which was to take place the same evening (March 31st, 1847). I understood the explanation, and in my enthusiasm I exclaimed anch' io son. From that moment I commenced with ardor to study a science of which I had as yet only the feeblest notions."

Three years after, Nov. 15th, 1852, Goldschmidt discovered, with a small glass which he had just bought, a planet which received from Arago the name of Lutetia, having the brightness of a star of the 10th magnitude. The 26th of October he discovered Pomone, which resembled a star of the 11th magnitude. He afterward successively discovered the following: Atalante, Oct. 5th, 1855; Harmonia, March 31st, 1856; Daphne, May 22d, 1856; Nysa, May 27th, 1857; Eugénia, July 11th, 1857; Melete, Sept. 9th, 1857; Palés, Sept. 19th, 1857; Doris, id.; Europa, Feb. 6th, 1858; Alexandra, Sept. 10th, 1858; Danae, Sept. 19th, 1860; Canope, May 9th, 1861. By reason of these discoveries he several times received the astronomical prize from the Academy of Sciences. He also determined the position of more than ten thousand stars which before had no place upon any known map of the heavens-and it was among these stars that he found the planets previously enumerated.

He made these discoveries with a small glass-and his observatory was situated in one of the most frequented streets of Paris. Not favored by fortune, Goldschmidt lived on a pension paid him by the French government. For a long time he had been troubled with his eyes, but this affliction affected him much less AM. JOUR. SCI.-SECOND SERIES, VOL. XLIII, No. 127.—JAN., 1867.

than diabetes, the symptoms of which he first felt in 1854. He then retired to the country, and for three years lived at Fontainbleau, dividing his time between painting and astronomy. Toward the latter part of last August his disease became complicated with other difficulties. He hastily finished his papers upon the physical constitution of the sun, and died on the 20th of August. He leaves a widow and two daughters without fortune. They will doubtless be adopted by the "Société de Secours Amis des Sciences."

Spectrum of aqueous vapor.-We now know the nature of the rays which Brewster discovered in 1833, and which have since been termed telluric or atmospheric. M. Janssen has made several investigations under the patronage of the Minister of Public Instruction, and has found that these rays are occasioned by the vapor of water. By means of new optical dispositions he has proved that the bands of Brewster were formed of fine lines, like the lines of Fraunhofer, and that they were constant in the spectrum, though of variable intensity according to the height of the sun. Relying upon this character of the telluric rays he has made a chart of the spectrum in which the distinction between the solar and telluric rays is clearly shown.

Janssen has also made numerous other experiments. In September, 1864, from the summit of the Faulhorn, he observed the rays of terrestrial origin and found they became weak in proportion as they were elevated and as the light had less thickness of atmosphere to traverse. In the same year he made an experiment upon Lake Geneva, and by reason of the humid air of the lake he was able to reproduce the same rays artificially. The flame from a large pile of pine wood at the distance of 21 kilometers presented these lines, but when viewed at a less distance no ray was visible except the brilliant one of sodium. Janssen stationed himself on the side of the lake opposite the fire, so that the light from the blazing pile, which was on a level with the surface of the water, might penetrate strata of air saturated with moisture.

It was necessary to ascertain if these effects were caused by the water in solution in the atmosphere, or whether, as Mr. Secchi thought, they were to be attributed to the vesicles of which mist and fogs are composed. A direct experiment confirmed him in the opinion that they were produced by the vapor. Janssen operated with a tube thirty-seven meters in length, which was filled with vapor by a steam engine of six horsepower. Care was taken to prevent the tube from cooling, and the light was furnished by a flame of gas placed in the axis of the tube. When the light passes through the tube filled with vapor subjected to the pressure of seven atmospheres it shows the principal telluric rays, among which Janssen places the

groups A and C and a large part of B, contrary to Kirchhoff, who attributes A and B to potassium. The red and yellow of the spectrum of water-vapor are more brilliant than the blue and violet. Therefore the color of the vapor of water should be orange; hence, also, the red of the setting sun, that is, of the sun seen near the horizon. Janssen does not agree upon this point with the conclusions of Prof. Cooke, which were pub lished in this Journal for March, 1866. According to the latter the vapor of water absorbs most completely the yellow and the red rays, hence the blue rays predominate in the spectrum that is transmitted. Prof. Cooke has, however, discovered and demonstrated by his own researches (this Journal, [2], xli, 184, also Journal de Pharmacie et de Chemie, June, 1866, p. 480), the influence of the vapor of water upon the phenomenon in question.

A new property of magnesium.-One evening while preparing some perchlorid of manganese, MnCl2 (this Journal, [2], xli, 107), with the peroxyd of manganese, the chlorhydric acid of commerce and ether, I observed that the color was not green, as it appeared to be in the daytime, but black. I was using gas for a light, and substituted in place of it first an oil lamp and afterward a wax candle, but the effect was the same, the color still appeared only black.

The green color reappeared by the flame of magnesium, which comports itself in this respect like the light of the sun. It is well known that bright-tinted flowers, colored stuffs, or pictures, exhibit much less brilliancy of coloring by wax or even gas light than when seen by the light of day, and should an artist, at the close of the day, wishing to supply the waning light, continue his work by the aid of wax lights or gas, he would be surprised the next morning at the assemblage of colors he had made the evening previous. They would in no way represent his thought, so different would they appear when viewed in the two lights.

By burning a thread of magnesium a light may be obtained which will make these colors appear the same as when seen by sunlight itself. Colors do not mingle or interchange by this light as they do by ordinary lights. Green does not appear to be blue in it, neither does blue have the slightest appearance of green. In short, all shades preserve the same appearance as when viewed in the full light of day. The flame of magnesium is whiter than solar light, and the blue predominates in it. Chemistry aids the painter not merely by furnishing colors more or less bright, but it now gives him a new mode of illu mination by means of which he can labor at night without fear of optical deception, as well as if it were daylight.

The influence of sodium upon flame.-On inquiring the reason for the extinction of color by the usual flame, which we have

just been discussing, it will be found that numerous causes produce this effect, one of which is sodium, which burns with a yellow (monochromatic) flame, that may be obtained either by bringing common salt supported on platinum wire into the flame of the Bunsen lamp, or by burning alcohol saturated with salt. All the colors are altered by this flame, with the exception of blue-violet, which is complementary to the yellow. Red appears black or white, sometimes bluish when it contains blue (see below, physiological effects). Mixed green appears yellowish or bluish (chlorophyl Schweinfurth green). The pure greens appear black (ex. MnCl2, MnBr2, MnI combined with ether, BaO MnO3, Cr2O3, gold leaf seen by transmitted light, Cr Cl3, &c.). Vide Annales de Chem. et de Phys., [4], viii, 298, for the enumeration of the various colors which have been experimented with.

The following table gives the result of some trials which I have made with a spectrum prepared by applying pigments to white paper. We give the composition of the spectrum and the colors with which it was obtained.

In this spectrum so wonderfully changed by the flame of alcohol saturated with salt, sunlight and the flame from magnesium instantly restored the normal colors, even while the sodium flame was burning in the neighborhood. They also reappeared by gaslight, but with much less intensity, and when the colors are not very brilliant they are modified as if they were illuminated by the soda flame.

Thus etherial solution of perchlorid of manganese when impure appears by gas light black instead of green. A mixed green composed of chromate of lead (PbOCrO3) and ultramarine behaves in the same manner.

If the illuminating flame were saturated with sodium its extinctive effects would be still more energetic, ordinary flames containing but very little of this metal. Spectral analysis shows us that instead of completely-extinguishing colors it merely alters them a degree more or less, darkening some and enlivening others, and creating confusion between blue and green.

The small quantities of sodium which all ordinary flames con. tain, are derived from several sources, viz., the mineral matters of wicks of lamps and candles, ashes of fuel and atmospheric air, which last, according to Bunsen, always contains traces of it.

Vogel has determined the proportion of soda which illuminating gas contains (Journ. de Pharm. et de Chem., October, 1866), and Mulder has shown (in the same Journal, May, 1866), with what facility marine salt volatilizes when heated with coal.

Small as the quantity of sodium is which illuminating gas contains, it is sufficient to affect certain colors, and to produce on a small scale all the effects of absorption or extinction which are readily seen in a flame saturated with it. Examples of this may be seen in certain green colors mentioned above.

Physiological effects of the monochromatic flame.-The foregoing results explain a well known phenomenon, which has hitherto never been accounted for. In the flame of alcohol and salt, the hands and face appear of a livid green hue, while the lips change to a blue-violet. This livid tint is known to all who have seen punch or a pudding burn, and is due to the alcohol more or less saline which is employed in these mixtures. Workmen at furnaces and forges are familiar with these peculiar tints, which appear upon the features illuminated by their fires.

In the first case the effect is produced by the NaCl which the alcohol contains of itself or which it derives from the alimentary substances; in the latter case the soda is obtained from the dross, and ashes of the combustible matters. The question arises, why under these conditions, the natural flesh color is changed to a bluish or livid green. The reply is evident. It has been shown above, that the colors which best resist the extinctive effects of the soda flame are those which come from blue.

That there is blue in human blood may easily be seen by the color in daylight of the large veins on the skin of the hand. All the other tints which enter into the composition of flesh color being extinguished except the blue, that shade alone remains upon the face of the experimenter, but being also illumined by a yellow flame, it is plain that the effects of the two colors will be to produce a green, varying in shade from yellowish to bluish according to the intensity of the blue, and producing a most sinister aspect on the human countenance. The eye speedily accommodates itself to these effects, but I have good reason for thinking that one cannot with safety, continue to work for any great length of time by this monotonous light. The retina after a time becomes so much affected as not to be able to bear without irritation either daylight or the ordinary illumination used at night, a result possibly caused by the absence of chemical rays in the flame, or because it injures the optic nerve which is poorly adapted to such a medium.

After sitting for a considerable time in the soda light, there comes a time when it is difficult to distinguish between the different shades of the same color. I have many times seen a tuft of leaves appear of the identical shade of the hand which held it, so