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THE HYMN OF A WOMAN'S SOUL.

L

OVE me, my Love! mine eyes alone can tell

The heart's enrapture at its own undoing;

Your Love's a golden bucket at the well,

And draws my deepest tears with its sweet wooing.

'Tis dim divineness in mine ears all day,
And in the night I wake to hear it pealing

Grand organ tones, that bear my soul away

To kneel where all the loved in Heaven are kneeling.

It grows within my veins, and is their blood

Throbs through such hopes and fears as make up madnessYea, broods like God's dear love within the bud

That bursts, and breaks its very heart for gladness!

ERIC S. ROBERTSON.

IF

SCIENCE NOTES.

IS THE FULL MOON RED-HOT?

F Professor De Morgan were still living, the following would expose me to the risk of being immortalised on the gibbets of a new edition of his book on "Paradoxers," i.e., scientific heretics, a class of unfortunates with whom I do feel a sort of sneaking sympathy in spite of having received some ridiculously insolent letters from their most outrageous representative.

Thirteen years ago, when writing "The Fuel of the Sun," I stated in Chapter VII. reasons for concluding that the intrinsic brilliancy of the lunar surface is, relatively to that of the sun, much greater than is usually supposed, and similar reasons apply to the superficial lunar temperature.

On the 23rd August, 1877, the moon was totally eclipsed, and being benighted in the course of a solitary walk through the wild region between Castlebar and Ballina, I was practically interested in the amount of light supplied by the moon.

At the commencement of totality this was considerable, in spite of the complete envelopment of the moon by the earth's shadow. The visibility of the heavy isolated mass of the Nephin mountain, lying some miles to my left as I walked down the Moy valley, served as a rough photometer.

This, and direct observation of the moon itself, indicated a steady diminution of luminosity of the shaded portion as the eclipse progressed, which was not merely a deepening of the shadow as the moon approached its centre, but a gradual darkening of the moon's surface, which continued until the termination of the eclipse.

Until the last eclipse (December 5th) I have had no other fair opportunity of repeating this observation, but did so then deliberately, using a good binocular field-glass, which was sufficient for my purpose. The result was remarkable.

When the partially-eclipsed moon first became visible at a little past five, the shaded part displayed a full copper-red colour; as the eclipse progressed this advanced to a darker or more obscure copper

colour; then the redness gradually faded, and the shaded portion of the moon grew darker and greyer, until at last it became of a dark slate-colour, and its outline or "limb was barely traceable towards the end of the eclipse.

In some elementary treatises this copper colour is attributed to "the refraction of the sun's light by the atmosphere of the earth." I fail to see how this can operate in the middle of the shadow, where it is the most decided, and why it should fade as the eclipse progresses, and finally be lost just at the outer edge of the shadow.

The Illustrated London News of January 7th states that in a lecture at the Royal Institution, Prof. R. S. Ball attributed this red illumination of the eclipsed moon to earth-light. This must be a reporter's error; so able an astronomer as the lecturer knows that there can be no earth-light on the full moon, whether eclipsed or not.

I believe that the surface of the moon is, as it appears to be, of a dull red heat, and that this high temperature is due to the action of the sun's rays striking it directly without any intervening shield of aqueous vapour or other atmospheric matter. If the volcanic tufa, of which the moon's surface is evidently composed, resembles the corresponding material on our earth, it is one of the best absorbers of heat and the worst of conductors.

This being the case, the uninterrupted glare of the sun's rays would produce its maximum possible effect on a thin film of the moon's surface; and as radiation and absorption are co-equal, this surface would rapidly cool by uninterrupted radiation while screened by the earth's shadow.

We must remember that a dull copper-red heat, just visible in the dark, is considerably below the temperature of red heat visible in daylight. Supposing the colour of the moon to be due to such heat, I should estimate its surface temperature at a little above 600°. Daniell's pyrometric experiments indicate 980° as the temperature of red heat visible in daylight. Another table ("compiled from various authorities ") which I have before me states the temperature of "lowest ignition of iron in the dark" at 635°.

This hypothesis of a red-hot moon is not so dangerous a venture now as it was when I was writing "The Fuel of the Sun," for at about the same time Lord Rosse was making some experiments by means of one of the great Parsonstown reflectors, using a vessel of hot water as a standard of reference. He concluded that the surface

temperature of the moon was 500° Fahr.

In connection with this subject it must be remembered that "red heat" is not an absolute temperature; it varies with the heated

surface when viewed in the dark.

Thus, if a piece of bright platimade be heated barely to red

num on which an ink mark has been ness, the ink mark shows out as though hotter than the metal. The dross on a ladle of melted metal shows a red heat, while the metal itself is dark. If a figured tile with black and white pattern be heated to redness, and seen in the dark, the black glow is so much more vivid than the white that the pattern appears reversed. If the pattern be in glazed and unglazed surfaces, the unglazed shows a red heat at lower temperature than the glazed.

A tufaceous surface like that of the moon is specially favourable for such display of red luminosity at the lowest possible temperature. Therefore the copper colour may be brought out by a temperature of about 600°.

The reasoning that ascribes so high a temperature to the side of the moon presented to the sun must lead to the conclusion that the dark or night side is intensely cold-that sunset on the moon is followed by such active, uncompensated radiation that in a few hours after darkness the red-hot surface must cool down to a temperature below the coldest of our arctic or antarctic regions, and the copper-red heat must return in a few hours after sunrise.

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A CHEMICAL CHAMELEON.

S everybody knows, white lead is the basis of ordinary oldfashioned white paint; but modern chemistry is not quite satisfied with it, for at least two reasons.

It is poisonous, and produces "lead colic " in some cases, though, as far as I have been able to learn by direct inquiry among painters, those who are careful and cleanly are rarely troubled with this malady

The other objection is that it is liable to change colour, to become nearly black under certain circumstances. This arises from the fact that the white lead, which is a carbonate, is decomposed, and becomes a black sulphide of lead, when exposed to sulphuretted hydrogen gas. In my opinion, this is not a defect, but a very meritorious quality, as the blackening agent is one of the constituents of sewer gas. Such being the case, the darkening of the white paint is a useful tell-tale.

I will not, however, enter further into the discussion of the merits and demerits of white lead, but simply state the fact that of the many substances offered as substitutes, the most popular are the oxides and sulphides of zinc, both of which are white. These are

used separately or mixed, or with the addition of barium sulphate, or sulphide, both very dense, like white lead, and too commonly used in adulterating it.

A gate-post, painted with this complex paint, was observed by Mr. T. Griffiths to behave very strangely. It was black all day and white all night, turning black each day just after sunrise, and whitening soon after sunset.

Dr. Phipson, an expert in that ghostly department of chemistry, phosphorescence, investigated the subject, examined the gate-post, and samples of the paint. He found that its chameleonism was due to the barium sulphide used in preparing the paint, for when that was omitted the paint displayed no eccentricities. He also found that the weird gate-post and other surfaces painted with the changing pigment remained of unchanging whiteness when covered with a sheet of ordinary window glass.

Carrying on his investigations still further, he has now succeeded. in separating the active agent from the zinc and barium compound, and the iron and other impurities of the original paint, and believes that he has discovered a new metal, to which he gives the appropriate name of actinium. The quantity of this which he found in the paint was 4 per cent., a very large quantity for a hitherto unobserved substance.

He separated the oxide and the hydrate of this metal, and found them unchanging in light and darkness, but in the sulphide of the actinium he demonstrated the concentrated mutability. It is canarycoloured when first prepared, and retains this colour in the dark, or when kept in a bottle, or otherwise protected by glass; but when exposed to direct sunlight it rapidly darkens and finally becomes quite black.

As several recently discovered new metals have proved to be mistakes, one is at first a little sceptical on this point; but, be it due to a new metal or a new compound of older acquaintances, the substance thus separated by Dr. Phipson is exceedingly interesting, and appears to me likely to become of great value as an instrument for investigating some of the mysteries of solar and other radiation.

That it should be so differently affected by the light before and after its passing through so transparent a medium as a piece of window glass, indicates a marvellous degree of special sensitiveness that opens out a wide field of experiment and speculation.

What is it that darkens this sulphide? It must be some element of solar radiation which window glass has the power of effectually ifting out. How is it affected by other light-sieves of varying colour

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