pupæ in (B) and four pupæ in (A). The candle was now removed.

At 6.20 I took the formicarium in a cab to a lecture I had to deliver, and at 7.30 I uncovered the bell-glassthere were now no pupæ visible and but very few ants. I applied the light towards the close of my lecture at 9.15, and at 9.30 numbers of ants put in an appearance, and there were many pupa in the upper chambers.

The nurses were busily occupied in carrying their youthful charges into the upper chambers.

A working-man told me, after the lecture, that his father often hung up things to a beam in a hothouse to tempt the ants, eg. a melon. The ants were some time before they discovered the prize, but the first to find it always went back to inform the others, when they came in large numbers to enjoy the fruit. The hardy son of toil added, 'So it appears the ants are not selfish.'

I then returned to Fleet Street. It was now past midnight-12.15. I examined the formicarium; only one pupa was visible in a passage very low down. The passage (X) I found in a great measure obliterated again. At 12.17 there were no pupæ visible.

At 8.30 the next morning, April 2, there was rain. I uncovered the glass.

At 9.50 I noticed that two pupa were carried up and disappeared in (A).

The red ants gathered under a stump (T) and the black ants, Formica fusca, upon it. The yellow ants had nearly restored their work of yesterday in (X), which had been obliterated by the homeward journey.

At 12.55 there were twenty-two pupa in chamber (B) cherished by the nurses. The sun was now shining on the formicarium. At 4.0 no pupa were visible, the formicarium being in the shade.

To prove that the ants are attracted by the light because of the heat with which it is associated, I may mention that

when the candle was placed close to the glass in order to illuminate the chambers of the formicarium, the glass had become warm, and thus a temporary source of radiant heat. Upon the withdrawal of the light the glad and willing movements of the ants are not checked, but are

FIG. 5.-The author's formicarium (front view).

A, B, g, K, o, chambers; T, stump; a and b, narrow strip of paper as a guide to observation; W, encircling trench with water in which the vase and stand are placed.

still directed to the chamber or chambers recently illuminated, but now in comparative darkness.

I have noticed also that the chambers at that side of the formicarium next a fire are always sure to be crowded by the ants, though the screen intervenes. The screen,

opaque to the luminous rays, is, as it were, transparent to the radiant heat. When the sun shines upon a formicarium, the ants are certain to be attracted to the surface, and manifest signs of pleasure and satisfaction; and when the sunbeams fall upon the screen which covers the sides of the glass vessel in which the colony is established, the ants

gather in the chambers and passages beneath the illuminated screen, bringing up with them not only the larvæ and pupæ, but the eggs also, to benefit by the genial warmth.

The observations above recorded show that ants are attracted to the sunlight, and bring their young beneath its

FIG. 6. The author's formicarium (back view).

Z, 4, 5, 7, 8, chambers; X, passage; T, stump; a and b, narrow strip of paper as a guide to observation; W, encircling trench with water in which the vase and stand are placed.

influence for the sake of its warmth, in the same way in which they are attracted by the light of a candle placed close to the sides of the formicarium; the glass through its means becoming a source of radiant heat.

CHAPTER IV.

Continuation of the subject of the effect of light and colour on ants -The prismatic colours possess different powers of illumination and varying degrees of heating power-The invisible rays at each end of the spectrum-The different coloured rays, as well as the invisible rays, possess more or less of chemical action-The significance of Mr. Busk's suggestion that certain colours are avoided by the ants because the chemical rays are distasteful to them-Professor Tyndall's demonstration, after Melloni, of the diathermancy of bisulphide of carbon-Sir John Lubbock's experiments with bisulphide of carbon and sulphate of quinineHis inference therefrom, and how far it should be modified.

LET us now see what inferences may be drawn from the beautiful experiments of Sir John Lubbock. The white sunbeam, when made to pass through a prism, is found to be composed of seven different colours, viz. violet, indigo, blue, green, yellow, orange, red. These differently-coloured rays possess also different powers of illumination, those rays nearest the centre being more luminous than those nearest the two sides of the spectrum. The lightest green or deepest yellow, occupying a central position in the sevencoloured band of light, would manifest most intense illuminating power. The different colours also possess varying degrees of heating power.

This fact was discovered by the illustrious Herschel1 when viewing the sun through his telescope, which he had darkened by glasses of many colours. He at one time

1 See The Popular Encyclopedia, article on 'Light,' p. 465.

experienced a powerful heat with a feeble light, at another, but little heat from a strong light. The result of his careful observation led him to conclude that the greatest heat was associated with the red rays or just beyond them, and the least with the violet or just beyond them.

Again, it is clearly established that, in addition to the coloured rays which are sensible to our sight, there are invisible rays on each end of the prismatic spectrum; the ultra red manifesting the greatest amount of heat, and the ultra violet the least. But though the latter have little heating power, they possess the more abundant measure of chemical action. Some think that all the coloured rays possess this attribute more or less; the violet in the highest degree and the red in the least. Others have found that though it is certainly true that the greatest chemical action is exercised just beyond the violet ray of the prismatic spectrum, and that the spot next in energy is occupied by the violet ray itself, and that the property gradually diminishes as we advance to the green, yet beyond this colour it seems wholly wanting. Judging from the above considerations, we gather that 'sunbeams, in traversing a coloured glass, produce similar effects to those caused by the differently coloured portions of the spectrum.'

With the guidance of this certain conclusion, let us now turn to the most characteristic experiments of Sir John Lubbock. In a deeply interesting and instructive paper, read by him at the Royal Institution of Great Britain on May 9, 1879, kindly presented to me by the author, he says,1 'I procured four strips of glass, similar, but coloured respectively green, yellow, red, and blue, or rather violet. The yellow was somewhat paler in shade, and that glass consequently more transparent than the green, which, again, was rather more transparent than the red or violet. I then laid the strips of glass on one of my nests of Formica

1 See Proceedings of the Royal Institution of Great Britain, vol. ix. part ii. pp. 188-190.