July 24, 1884] 



NA TURE 



and there is apparently an absorption of energy which does not 

 appear either in the form of expansion or of sensible heat as 

 temperature. At this high stage the specific heat of some of the 

 simple gases has increased threefold, while some gases have a 

 greater rate of expansion than others. 



The same thing occurs with other simple gases, but at a much 

 lower temperature, as, even within o° and 200°, where dissocia- 

 tion cannot be entertained, chlorine and other halogens differ 

 considerably from N or H, and at 1600°, if an air thermometer 

 indicated 1600 for a given expansion, a chlorine one would 

 register by expansion 2400 for an equal temperature, though 

 with a much greater absorption of heat by the chlorine. 



This difference is dependent on the fact that at 1600 the com- 

 parative density of chlorine has diminished one-third ; or, in 

 other words, that its volume, as compared with H, instead of 

 being 1, has become i"5 ; or, to put it in another way, that 

 under these conditions, the specific heat of CI is threefold that 

 of H. 



Quite apart from these extreme cases the specific heat is never 

 a constant value ; it takes more heat to raise a given weight of 

 substance i° at one temperature than another. 



The specific heat increases with temperature, but differently 

 for different substances : — 



Iron 



Platinum 



Mercury 



The differences here are both distinct and small, but Be 

 (glucinium) increases twofold within a moderate range, and we 

 have seen that between - 50° and 600° carbon increases its 

 specific heat sevenfold, or, as Mr. Sprague expresses it : "The 

 heat relation of each substance is described by a particular curve ; 

 and the small differences observed in some cases are not errors, 

 but actual differences of the several curves, and where there is 

 approach to identity it is accidental, due to the temperature of 

 observation being within a limit at which the curves are near 

 their commencement, and have barely begun to separate." 



However tempting or fashionable it may be to rush into hypo- 

 thetic explanations of half-digested truths, yet I have taken some 

 pains to keep within facts, which are in some respects incipient 

 and but little understood. 



If the causal differences in the production of light and sound 

 had been fairly or patiently entertained, the "luminiferous ether" 

 would never have been invented, which now crosses our path, as 

 an "opaque fact, stopping the progress of further knowledge." 



If a little more humility and patience had been evinced in 

 respect of the expanding facts connected with gaseous volumes 

 and specific heats, the old equivalents would never have been 

 doubled, trebled, or quadrupled, to mar the symmetry of a 

 beautiful science. 



I quite agree with M. Troost, who, in repudiating the hasty 

 references to dissociation, &c, observes: "The only conse- 

 quences which necessarily flow from the experiments at high 

 temperatures, or at low pressures, are that the coefficient of 

 expansion is variable with the temperature, or that the coefficient 

 of compressibility varies with the pressure." Also with the final 

 conclusion of M. Berthelot : "The only law absolutely and 

 universally applicable to the elements is the invariability of the 

 relations of weight according to which they combine. This 

 notion, and that of the energy brought into play in their reactions, 

 are the sole and only firm foundations of chemical science." 

 Samuel E. Phillips 



A Ca'nivorous Plant 

 With reference to Prof. Moseley's letter in your issue of May 

 22 (p. 81) on "A Carnivorous Plant preying on Vertebrata," 

 I may mention that in 1 88 1, when surveying at the Paracel 

 Islands in the South China Sea, I saw a somewhat similar oc- 

 currence. The tide was low on the reef on which I was strolling 

 and admiring the lovely forms of coral existence. As I neared 

 a pool cut off by the tide from the sea, I noticed amongst other 

 submarine verdure a very ordinary-looking flesh-coloured weed 

 about one foot high and of similar girth. My appearance 

 alarmed numbers of tiny fish, which darted to the cover of 

 overhanging ledges, but I noticed about half a dozen apparently 

 seeking cover in the weed. Bending down closer, I saw that they 

 were lying helpless about the fronds, with very little life left in 

 them. Putting my hand down to pick up one of the half-dead 

 fish, I found my fingers sucked by the weed, the fronds of which 



closed slightly on them. The fish were not caught by the head 

 especially, but held anywhere round the body. The death 

 seemed to be slow and lingering, and where the fish had been 

 held its skin was macerated. These captives may have been 

 caught some time, and were in different stages of exhaustion. I 

 regret being unable to name the plant, or the young fish. They 

 were from an inch to an inch and a half long. The plant had a 

 dirty and rather slimy look about it. Alfred Carpenter 

 H.M.S. Myrmidon, Suakim, Red Sea, June 24 



Phosphorescence of the Jelly-Fish 

 The conclusions arrived at by Mr. Verrill (Nature, July 17, 

 p. 28 1) cannot fail to be of interest to all who have ever specu- 

 lated on the significance of the luminosity displayed by so many 

 Acalephte, Meduses, and other marine organisms. When in the 

 tropics, in 1875, verv similar ideas occurred to me, and in an 

 address on the phenomena of cyclical propagation delivered to 

 the Essex Field Club on January 28, 1882, I ventured to put 

 forward the following views, which, as the address is still in 

 manuscript, I will beg permission to quote : — " It was in the 

 Bay of Bengal, when on the Eclipse Expedition of 1875, that I 

 first saw shoals of Meduscs in their full splendour. Speculating 

 on the meaning of the vivid colours and brilliant phosphor- 

 escence of these creatures, I came to the conclusion that both 

 these characters might be protective danger-signals of the same 

 nature and fulfilling the same function as the bright colours of 

 distasteful caterpillars according to Wallace's well-known theory, 

 or the phosphorescence of the Lampyridce ace rding to Thomas 

 Belt ('Naturalist in Nicaragua,' p. 320). The 'urticating' 

 powers of the jelly-fish would certainly make them unpleasant, 

 if not absolutely dangerous, to predatory fish, and their bright 

 colours and luminosity at night may thus be true warning 

 characters." R. Meldola 



London, July 21 



Fireball 



Recorded personal observations, such as that of Miss Annie 

 E. Cocking (Nature, p. 269) last week, must needs be so rare 

 that every detail of them — especially where the description is 

 clear and simple — is of weight and value. What strikes my 

 own mind as of much interest in this one is that, as the strange and 

 fateful visitant sank towards the carpet, " at this instant a peal of 

 thunder crashed over the home — it was the very loudest the 

 writer had ever heard." This would seem to show that, what- 

 ever the nature of the insulator which envelopes these floating 

 Leyden jars, their connection is maintained unbroken with the 

 cloud of origin until the moment of discharge ; and that, what- 

 ever causes the " crash," a peal of thunder takes effect rather in 

 the cloud than at the point of contact. This agrees also with 

 the descent of a fireball in the sea at Margate, mentioned in 

 to-day's papers, where the crash of thunder occurred while the 

 ball was yet in sight. But it is still another question whether 

 these floating globes, which only discharge themselves on contact, 

 do not in some important respect differ in their nature from the 

 commoner "fireball" discharged with the directness, if not all 

 the speed, of a lightning flash out of a thundercloud. It is a 

 question towards the solution of which only observations such 

 as that for which we are indebted to Miss Cocking can mate- 

 rially help us. Henry Cecil 



Bregner, Bournemouth, July 21 



Animal Intellig. nee 

 The following instance of animal intelligence may interest 

 some of your readers. While walking through the forest here 

 the 1 ither day, I found a young jay upon the'ground scarcely able 

 to fly. As I stooped down to examine it I was somewhat 

 startled by a swoop made at my head by the old birds, their wings 

 actually touching my hat. Determined not to be driven away, 

 I remained by the young bird, whereupon a succession of like 

 swoops were made at my head; these I easily succeeded in 

 parrying with my stick, although the old birds frequently came 

 in different directions. After about a couple of minutes the old 

 birds seem to have come to the conclusion that nothing could be 

 achieved in this fashion, and one of them, flying to some little 

 distance, kept calling to the younger one, who half hopped, half 

 flew after her. I of course followed ; and now occurred what 

 seems to me a striking instance of animal sagacity. The pines 

 here are covered with lichen and a long, hairy kind of moss, 



