\f\V. 191. 



KNOWLEDGE. 



The melting of an iceberg is accompanied — especially in 

 calm weather — with the production of fog, because the air in 

 the neighbourhood soon becomes supersaturated with moisture, 

 while the low temperature causes deposition of this moisture. 

 For this reason, and also owing to the peculiar cloud-like 

 aspect of an iceberg at night, the iceberg is not easily visible. 

 The danger is increased by the fact that the extent of the 

 iceberg may be far greater under water than it appears to be 

 above : the action of the waves help to cause a shelving away 

 of the berg near the surface of the water. The actual volume 

 •t the ice above water always has a fixed ratio to that below, 

 ibout as one is to eight. The detection of icebergs becomes a 

 matter of great importance to shipping — as has been so 

 deplorably made manifest recently by the disaster to the 

 ■' Titanic." The method by means of which the whereabouts 

 of an iceberg might be established cannot be numerous, for the 

 reason that the ice is much the same substance as water: one 

 could suggest, perhaps, a few possible methods of detection — 

 temperature of the water, or saltness of the water in the 

 neighbourhood of the iceberg. However, in a big pack or 

 icefield, the alteration of such properties of the sea water 

 would not be sufficiently great to be of practical value. It 

 would appear more practical to provide every ship with some 

 form of search-light which could be made to automatically 

 p.ass a very intense beam of yellow light across the course of 

 the ship from side to side. The yellower the light the more 

 fog-resisting the beam. This suggestion would seem the most 

 practical method of combating a danger which can ha\ e such 

 appalling consequences. The lighthouse is at any rate some 

 use in a fog. 



EMISSION OF ELECTRONS DL'KIXG CHEMICAL 

 CHANGE. — Lavoisier's principle that "matter is inde- 

 structible " and that " during a chemical change there is no 

 loss or gain of matter" has been proved by Landolt to hold, 

 so far as the most accurate balance can settle the i|uestion. 

 Hut since heat is often evolved during such a change and 

 since the force of chemical affinity appears to be of an 

 electrical nature, it is quite possible that the energy changes 

 entail loss of electrons — which would be quite undetectable 

 by the change in weight of the reacting substances. Professor 

 Habcr has recently made experiments on amalgams of sodium 

 and the other alkali metals and finds that in an exhausted 

 space containing small quantities of reacting gases, such as 

 bromine or phosgene gas. the metal acquires a positive charge 

 and negatively charged electrons are set free. Similar 

 experiments with quinine salts showed that they absorb 

 water and in doing so tend, owing to discharge of negative 

 electrons, to ionise the air. Gases, evolved by the action of 

 acids on metals. Sir J.J. Thomson showed to be ionised and 

 his interesting results were published in a book entitled the 

 " Discharge of Electricity through Gases." Such experiments 

 lead to the ijuestions " To what extent is the atom of an 

 element capable of undergoing change in electrical structure 

 before it ceases to behave in its own distinct manner ? " and 

 " To what extent is the atomic mass of an element an 

 invariable quantity ? " Does the " atomic mass vary with the 

 temperature ? " 



EXPLOSIONS. — .-\n interesting study of the radiation 

 during explosions forming carbon dioxide and water vapour 

 has been recently published in the October Philosophical 

 Transactions of the Royal Society, by W. T. David. The 

 results appear to show that when an explosion occurs the 

 vibr.atory energy is a maximum before the maximum pressure 

 is attained and. therefore, before the mixture attains the 

 maximum temperature. Hence it is probable that a consider- 

 able part of the energy of combination goes to set up internal 

 vibrations of the carbon dioxide and steam molecules : part of 

 this energy is lost as radiation and part is transformed into 

 rotational energy and translational energy, the latter causing 

 increase of pressure of the gases. The work of Professor 

 Dixon and also of Professor Hopkinson. on the propagation 

 of explosions is highly interesting and should be consulted by 

 those who wish to follow up the matter. 



ZOOLOGY. 

 By PROi-iissoR J. Arthur Thomson, M.A. 



INTELLIGENCE OF FISHES.— There are not many 

 precise data in regard to the intelligence of fishes. Some 

 observers say they can be trained a little ; others, like Edinger, 

 deny them even memory. It seems that the brain, of bony 

 fishes in particular, remains at a low grade. M. Oxner has 

 recently made some interesting observations at the Oceano- 

 graphical Museum at Monaco with a fish called Coris julis. 

 When he disguised the hook perfectly he caught the same fish 

 as often as he pleased. But that only proved that the disguise 

 was perfect and that the fish was appetised. 



In another set of experiments he used an e<|ually well 

 hidden hook, but placed a piece of red paper on the gut-line a 

 couple of inches above it. For the first week the fish (an 

 inexperienced one, of course) remained indiflerent; on the eighth, 

 ninth, tenth and eleventh days it took the bait ; on the twelfth 

 day it refused the bait till the red paper was removed ; on the 

 thirteenth, fourteenth and fifteenth days it refused the bait 

 with the red paper, though it examined it carefully ; on the 

 sixteenth day and on the following six days it began by 

 snapping at the red paper, and then turning to the hook bit 

 off the bait in small scraps, without any hurry, and with a 

 thousand precautions. 



It looks as if an association was here established between 

 the pain of being hooked and the red paper, and as if the latter 

 became a warning advertisement, inhibiting the instinctive 

 attraction to swallow the bait, literally putting a drag on the 

 animal's movements. Gradually, however, the fish regained 

 liberty of action, it disregarded the taboo, it very deliberately 

 experimented with the bait, it succeeded, and we say that it 

 "understood." .^pprendre, M. Oxner says, n'est que la 

 serie successive des essais reussis. 



RESOURCES OK THE SEA.— With the great resources 

 of the sea, such as fishes, whales, seals, turtles and crust- 

 aceans everyone is familiar, but the miscellaneous minor 

 treasures are less appreciated. It is interesting, therefore, to 

 take a concrete case, and we may refer to Alvin Seale's 

 account of the miscellaneous marine products of the Philippine 

 Islands. There are the trepangs or sea-cucumbers, a staple 

 food of all Oriental people ; Sharks' fins are dried, cured, and 

 exported to China as a basis for soup ; there is the window- 

 shell (Placiima placenta) the right vjilve of which is used 

 intact instead of glass in most of the buildings in the city of 

 Manila ; there are several Gasteropods, such as Trochus 

 niloticHS and Turbo niarnioratus. whose shells are used for 

 button-making : there are various corals (including apparently 

 the precious coral) useful for decorative purposes ; the black 

 antipatharian is used for making canes; there are several 

 edible seaweeds ; and there are sea-snakes whose skins make 

 beautiful leather. 



PURIFICATION OF OYSTERS.— Fabre-Domergue con- 

 tinues his important experiments on the purification of oysters. 

 He has tried keeping them in filtered artificial sea-water, 

 introducing a sand-filter into a closed circulation through a 

 series of tanks. He has obtained excellent results not only as 

 regards purification, but as regards the \itality and flavour of 

 the oysters. 



E.NPERIMENTAL REDUCTION OFWINGS.— J. Dewitz 

 returns to some very interesting experiments which he made a 

 dozen years ago on wasps (Po/isics). He placed the nests 

 for forty-eight hours in a refrigerator and found that this had 

 the result of hindering the development of the wings. Similarly, 

 with the pupae of flies (Calliphora), exposure to cold resulted 

 in defective wings. Extending these experiments, Dewitz finds 

 that chrysalids with shortened wings result when the cater- 

 pillars of Porthesia chrysorrhoea. just about to undergo 

 metamorphosis, are placed in an atmosphere containing hydro- 

 cyanic acid. It seems that a ferment (tyrosinase), which 

 occurs diffuselv in the larva, is localised in the wings of the 

 pupa, and the author suggests that the artificial conditions 

 noted above act prejudicially on the ferment. Perhaps the 



