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Title
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Scientific. Science Notes.
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Description
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Australasian (Melbourne, Vic. : 1864 - 1946), Saturday 24 March 1900, page 52
SCIENTIFIC.
SCIENCE NOTES.
By PUYS1CT
Tin: HEARING OR INJECT
Can insects hear? In order to answer this question it 'would seem necessary to demonstrate the possession by insects of t-oine organ that can reasonably be supposed to be ;i hearing one. Sounds are prop-agated by pul&ations or waves of the air. Ii there were no atmosphere the transmission of sound would not be possible. But even when sounds are produced there must be some means by which the vibrations may be conreyed to some part o! the nervou* s\>tetu and, so to speak, interpreted. A serie- of waves may strike a nerve and yet give rise to no sensation of any kind. Our organs of sight and smell are complicated structures, but they only respond to certain stimuli, and not to all. It seem- necessary, juc'giiig irom tbe examination of healing organs in different group1- <ii ;tiiiinnl>. that these should be some solid bodit.« which are s-et in motion by the air wave.-. These solid bodies then actually .-Hike wl.at. for our purpose, we may call the end of a nerve. The stimulus thus produced is transmitted in the ca=e of our-elve- to the brain, and is there interpreted .as a sound. In the back-boned annuals the place where sensations are perceived is the brain, but there is no reason why it should be so in all animals. There is no reason why, for example, the nerve mat- which perceives a sound should not be at one end of the body, that which perceives lieht at the other end. and that for the perception of an odour :n the middle. A s!ie!!-!isii. such as a cockle, has nothing resembling .1 brain, for it has no head, yet B'jine ?>! its allies have eyes for seeing, and an urtran probably akin to a nose in junction: it kno-vs how to keep the right way up and 'i-irt to search for its food. lhis being so. it does not follow that even if an animal has a head and something akin to a brain thf.t we are to believe that all
.jrc /-crcejvcd in this brain. We are not i" -11; pose- that if an animal has an on: an ca table of receiving vibrations of the air that :ht- nerve from that organ must lead t" tl.e br.iin in order that the sounds may be j-eweivtfd as such. The nervous centre, as it i- termed, for the organ may, in l'act. be piaced anywhere, and in the same y 1 lit* part of tbe body which is ni'id'Met i'.i receive the stimulus may be anywhere.
') his beinc so, there is no reason why
should cxpeci a grasshopper s hearing ore ui t » be ;;i its head ot its centre for the inU'ipTctauon in the brain. What we have tf- look for is something which will be riuved by sound waves, and so irritate a rr-rve ending. In many animals tlitre are additions made to these simple essentials, such as a sheet of tightly-stretched membrane expose a larger surface to the impact of the air waves. This is called a tym: aiiiim. or drum; while to tins is sometime- ii'hled. as in ourselves, an external fold of sl::n to collect a still larger numlier of wave- and convey them to the drum. Nov.- ;;n organ, almost certainly for bearing, is found in the locust, and is placed on the abdomen, or that part oi the body behind the legs. There is a tight membrane stretched on a horny ring, and tn the middle of this are fixed a couple of iiurd plates, which support a bag of fluid. To this bag runs a nerve, which leads back, not to the brain, but to one of the ganglia of the thorax. This organ certain!'.- locks like a hearing organ, and is generally accepted as such. In j-ome of the green grasshoppers an organ of similar stiiicture is found, but it is placed, not on the abdomen, but on the front legs. In the vvater be:-tie the hearing organ seems to be situated in the antenna?, or so-called feelers or horus, and there are other modifications. It may lie asked why not make poises and see if the insects pay any attention to them. A little while ago it was pointed out in this column that when the vibrations rise above a certain number to a second we can perceive no sound, but it does not follow that no animal cannot do so. Many insects are provided with somewhat complicated sound - producing organs, and were their fellows deaf the reason for the existence of these organs would be difficult to explain. But as we find the sound-producing faculty is generally associated in the same insect with what appears to be an organ of hearing, we would eecm to be justified in answering the question, "Can insects hear?" in the affirmative.
THE ORIGIN OF MAGNETISM.
The actual cause of magnetism is unknown to us; and till within the last few weeks no light whatever had been thrown on the subject. It appears, however, that Professor Rowland has bee® engaged for some time on experiments which, if all we hear about them is true, will go far towards an explanation of the origin of terrestrial magnetism.
So far as the course of tbe investigation has yet been made public, it appears that the professor wound a length of wireseveral miles of it-on a brass wheel, which he then set in rotation, and found that while revolving it behaved a8 a very weak magnet, the strength of the resulting magnetic field appearing to depend only on the speed of rotation. The magnetism is supposed to be due to a feeble electric current set up in the wire coil.
It has long been known that a wire coil in which an electric cujrent circulates has all the properties of a magnet; on this fact Ampere based his explanation of magnetic bodies. He supposed that the molecules were the seats of electric currents, and showed that, if such were the caee, the behaviour of steel magnets on dissimilar bodies could be accptinted for; 1»ut this only pushed the problem one step backward, aa the further question suggested itself, how are these molecular currents set up? The mathematical researches of Ixird Kelvin
J^ iim to surmise that something of the
jof n»Mion must exist in magnetised bodies; and a few years ago Professor Schuster mttgeflted, as a bare posMbttity, that every TaJnge rotating body
atbe a magnet, and proved th^t if euch
[ a reasonable theory of terres
be formulated on
:toi
doubt that a conducting body, when set in rotation, is so acted on by the cthcio spa.ce as to become a magnet. On the other hand, it is qui*"? certain that bodies at rest-such as the nee-die ot a compass
can be magnets: and it will be a simple ana obvious deduction from the espenmen s to ascribe their magnetism to the lm
rotations of their constituent molecules, which, might l>e supposed to set up eleotri
currents in their mass just as such currents are said to be set up in Rowland s coil.
A RED I.AKE.
The natron lake# of Egypt have long been known as a source of carbonate of soda, from the Arabic name fromwhich the words natron and nitre come, though themi^ily they ;-.re very different substance?. A German company is now walking somo of the :lakes in the LiKan Desert, and they were
recently visited by a bk>logi>T. w"ho no; iced and '.vjj puzzled by the led colour of tlie water. He v.v? told hy people living on the fi-ot ihat the rolour was due to the prosenc-e of the brine shrimp, which communicated its reddish tint to the water This explanation Mr. Dewitz. the scientist in Question, dismissed as untenable, since at the time of lr® visit no brine shrimps
wesunt. their s^i^on being past, msides." the.-e small so-called shrimps, like hmiiv of the irustacea. owe their colour to their blood and not to a pigment on the outer surface of their bodies, which coneeivablv migbt bo dj.-^olvtnl off at ue.un. Though he found no brine shrimps, he found some moMjuito larva?, w;iich normally are not red, though these were. 1 his showed that probably the mosquito larva? were red because the water was> red. and not vice-versa. The author tound that a red silt of an organic acid was present. Prcbabiv it is an iron salt, thugh he noes not siv ";o. As to the origin of the salt, ho a mi: be? it? formation to certain red bactena which are abundant in the w::ter. We know of variously coloured bacteria, some of which are very highly tinted. The small bright pink spots. for instance, that are sometime- seen in bread are due to bacteria belor.gine to the same group, and which, like "by far the greater uumber ot bacteria, are in no way harmful to man.
A CHEAT MODKKX INDl'STRY.
The electrkal production of refined copper is an industry of very reccnt date; hut it ha^ already assumed gigantic proportions. Brought into use about a quarter of a century ago. it was then employed on a very small scale, about twenty tons j)er week being the world's output. This has now increased to five hundred tons pc-r day, or one hundred and eighty thousand tons per annum, the net value of the annual output being about nine millions sterling. Of almost equal importance are the by-products of the indus-try. Crude copj>er alwavs contains gold and silver among its impurities; the latter to a very large extent, its average being over one hundred ounces to the ton. To separate these from the copper bv the older process would cost more than they were worth; but the electrical proves* effect- a complete separation, and as the silver forms more than half of the total residues from the process its extrac
tion therefrom and the separation of the gold become profitable, the annual .net value of the preeiou* metals so obtained being about three millions sterling.
An industry so extensive is naturally the subject of continual modification and impiovement; ainoag the most recent of these is the direct proce.-s of manufacture of copper tubes. The met.i! is now deposited by the current on a rapidly revolving cylinder, instead of a flat plate, as in the earlier day> of the industry: as copper tubes are very largely used in the arts this is a valuable device, but it has other advantages as we!!. Under ordinary circumstances c-opr>ei tends to be deposited by the current in a somewhat loose state of aggregation, and to give the deposit the necessary hardness and density requires the continual action of the burnisher; but Mr. Cowper-C'olesthe inventor of the new method-finds that the friction set up by the rotation of the c-vlinder in the depositing solution answers the same purpose as burnishing, lie makes use of this fact in the production of plates and wires; to obtain a plate it is only necessary to slit lengthwise a tube of the proper size, and then flaiten it out; to make wires, a thin thread of some insulating substance is wound on the cylinder, and the copper deposited in the spiral groove left between the windings of the insulator. The thread of copper thus obtained is easily drawn down to the required gauge by ordinary wire-drawing tools. Tne process is not only convenient, it is cheap, too; the net cost of refining the copper in this way being less than 2 per cent, of the value of the finished product.
DESTRUCTION OF GADFLIES.
Fortunately in Victoria we are not much troubled by gadflies, which are such a scourge in some parts of the Northern Hemisphere. They do a considerable amount of injury to stock by biting, and so annoying them to such an extent at times that their condition is considerably reduced, while they are credited by their bites with occasionally transmitting anthrax to human beings. In the United States and in Russia the practice prevailed of rubbing cattle with oil in order to lessen the painful nature of their bites. This measure, however, is only a palliative, and does not prevent the attacks or destroy the pests. Professor Porch iuski, of St. Petersburg, has hit on a simple method of lighting this plague. The gadfly is a thirsty creature, and ie very fond of drinking from stagnant pools while on the wing. Daring the operation it touches-the water with the lower surface of its body, which is protected by a coat of long hairs, and so is not wetted by the act. Porchinski thought that if he could wet them they would be unable to. free themselves from the water, and so" would be drowned .--The idea of spreading a layer of kerosene on the water struck him, and he tried it with complete success. The amount used was about nalf-a-pint to the square yard, and was renewed every morning. The insects in attempting to drink were at once wetted by the kerosene, and, as it were, became stock to the surface of ine pooL The kerosene then rapidly killed them, and they floated ebout in small islands in the water in vast numbers. .Kerosene has been recommended as a meens of destroying mosquito iarvae, which are aquatic and-come to the surface ,to Jbreathe, which act they perform by thrashing their foils up intothe air^ Ifthe water be covered by a layer of kerosene they are killed by it, just SB many ^orchard pests are br spraying the plants with kerosene emul
sion. ,;
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Date Issued
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1900-03-24
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Creator
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Physicus
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Publisher
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The Australasian
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Location State Territory
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Victoria
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Location Town City
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Melbourne
