244 



SCIENTIFIC NEWS. 



[Mar. i6, iS 



as the broader ring is traversed, and then more and more 

 rapidly. Near the centre, where the isobars are very 

 close together, it has been known to fall an inch in 50 

 miles. Of course, as you recede from the centre 

 the barometer rises o'2o inch as you pass from 

 one isobar to the next outer one. So long as 

 the barometer continues to fall, the centre is getting 

 nearer ; when it steadies and begins to rise, this marks 

 the nearest point, and here the shifts of wind will 

 be the most sudden and violent and the sea highest and 

 most confused. The use of this diagram is to enable 

 the ship's position to be found with reference to the 

 centre of the hurricane, by means of the direction of the 

 wind and the fall of the barometer. If the vessel is 

 making any great way, the direction of the wind may 

 appear different from its true bearing ; this must be care- 

 fully considered, and it is best to heave to when observ- 

 ing. Suppose the wind is ESE, and the barometer 40 degs. 

 below normal. Find at the margin of the diagram the 

 wind arrow marked ESE, and follow the line in toward 

 the centre as far as the isobar marked four-inch; this will 

 give the position of the ship, and will give some idea of 

 the distance of the centre of the storm. The centre 

 should be marked on the sailing chart, and the operation 

 should be frequently repeated, marking the storm-centre 

 on the sailing chart ; every change of relative position can 

 then be watched, and the course can be made to run out 

 of the storm, or if that is impossible, to take such action 

 as may seem best, having regard to the speed of the 

 ship, the rate at which the storm is apparently travelling, 

 the lay of the land, and the passage that is being made. 

 The force of the wind is given in the figures of the 

 Beaufort scale. Fig. 5 is the storm card, with the sailing 

 instructions as recommended by the U. S. Hydrographic 

 Office. 



LUMINOSITY IN ANIMALS. 



/^NE of the greatest of the many mysteries which zoolo- 

 ^^^ gists have in vain attempted to solve is that strange 

 capability of emitting phosphorescent light which is 

 common to many of the lower forms of life. We find 

 it in various insects, of which the lantern-fly, the fire- 

 fly, and our own British glow-worm are very familiar 

 examples. We see it in certain of the myriapods, repre- 

 sented in this country by the well-known luminous centi- 

 pede. Above all, we find it in numbers of the jelly-fish and 

 their allies, from the large disc-bearing species, which 

 occasionally appear in such vast shoals, to the infinitesi- 

 mal atoms, which, although individually so small that 

 the unassisted eye can scarcely perceive them, yet throng 

 the water so densely that at night it appears like one 

 broad sheet ol living fire. The boat passing by leaves a 

 wake of light behind it, each splash of the oars throws 

 up the spray like a shovsrer of blazing jewels ; and when 

 the tide goes down and leaves the rocks and the beach 

 exposed, one sees the seaweed closely studded with 

 glittering points of brilliance, each like some tiny glow- 

 worni shining with pale radiance in the darkness. 



What is this light, and why is it given ? No man can 

 tell. Theory after theory has been put forward ; theory 

 after theory has been shown to be utterly false. The 

 luminosity is an evident fact, but no chemist can account 

 for its presence. Concerning its nature, its origin, and 

 its functions, we are still utterly and completely at 

 fault. 



Take the case of the glow-worm. Here we have a 



beetle with luminosity strongly developed, due, as we 

 easily find, to a certain liquid secreted within the body, 

 and in some mysterious manner under the control of its 

 owner, who can turn it on and shut it olT at will. Nothing 

 in nature is without its use ; yet of what service can this 

 light be to the glow-worm ? Is it a sexual attraction, 

 designed to guide the winged and active male to his grub- 

 like and crawling mate ? But the male possesses it 

 also, although not in equal degree, and to him, upon 

 such a supposition, it can be of no avail at all. And, 

 moreover, if such be the case, why do not other and 

 similarly constituted insects possess it ? There are 

 numbers of beetles, moths, and bugs in which the one 

 sex is winged and the other apterous ; yet we do not find 

 that any special attraction is necessary to guide the one 

 to the other. The female vapourer moth, a heavy, 

 clumsy, helpless being, who cannot even walk, much less 

 fly, is visited by suitors in scores, who detect her 

 presence from an almost incredible distance, and wing 

 their way with unerring certainty to the spot where she 

 is resting. They require no guide, other than that 

 strange instinct which all creatures alike appear to 

 possess. Why should the glow-worm need more ? 



The fact that both the larva and pupa are luminous, 

 which many writers have urged as an additional argu 

 ment against the theory of sexual attraction, has no bear- 

 ing whatever upon the subject. In them the phos- 

 phorescent capability is merely developing, just as are 

 the future organs of the imago, and luminosity in some 

 degree is inevitable from the very nature of the property 

 in question. In the larva the anatomist can trace the 

 rudiments at least of every organ belonging to the future 

 perfect insect, and it were strange indeed if the luminous 

 liquid and the glands which secrete it were suddenly to 

 come into being with the mere casting off of the pupal 

 skin. They, like every other part of the bodily frame, 

 must pass through their incipient stages, and the faint 

 light which we see in the glow-worm larva, and the 

 somewhat stronger radiance emitted by the pupa, are 

 the natural and inevitable concomitants of the developing 

 faculty which attains to its perfection only in the mature 

 beetle itself. 



Is this light granted as a protection from natural 

 enemies ? 



Scarcely, for its very nature causes it to act as a 

 source of attraction rather than as one of repulsion ; and 

 certainly the glow-worm is not rejected by insectivorous 

 animals. The present writer, for instance, once stocked 

 a small fernery with forty or fifty glow-worms, only to 

 find that they all perished in a couple of nights at the 

 hands, or rather the tongues, of the toad to which the 

 fernery in question served as a harbour of refuge. Since 

 a toad, as we know, will repeatedly swallow fragments 

 of glowing charcoal, it is scarcely to be expected that it 

 should be deterred by the pale cold light of the glow- 

 worm. 



Why is this light under the control of its possessor ? 

 Some say, to protect it from night-flying insectivorous 

 birds, at whose approach it can darken its gleaming 

 lantern, and so remain in safety until the danger has 

 passed away. But, I would ask, how is the beetle to be 

 aware of their presence ? Lying deep among the roots 

 of the herbage, how can it tell that a bird, and a bird 

 which is likely to devour it, is in its immediate neigh- 

 bourhood ? How is it to know that a toad or a frog is 

 dangerously near ? Even the vibration of a human foot- 

 fall does not alarm it, much less would the almost 



