THE EARTH'S MAGNETISM.-PROFESSOR ADAMS'S ADDRESS.

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HE opening address of Section A-Mathematics and Physicsby Professor Grylls Adams, is chiefly devoted to the molecular hypotheses which at the present time occupy so much attention. The address itself being an abstract, it would be vain to attempt any further abstraction, especially as the subject demands much explanation in order to render it generally interesting. At the conclusion, Professor Adams takes up a subject of more general interest-viz. that of the connection between the earth's magnetism and solar activity and ventures to put forth an explanatory hypothesis which demands no special invention of ethers or atoms, or other figments of mathematical imagination, but is based simply upon ascertained facts and established physical laws.

The existence of vast quantities of iron vapour in the solar envelope is one of the best-established facts of celestial spectroscopy. Although the magnetic properties of iron are greatly reduced by heating, "we have no proof that it has absolutely no magnetic power left." We also know that a body which is magnetically polarized induces a similar condition upon other magnetisable bodies in the vicinity, and that the earth, by reason of the iron it contains, is such a body, and therefore that the magnetic condition of the earth may possibly be induced by that of the iron in the sun; but whether to such an extent as to account fully for its polarisation as shown by the needle, is an open question.

There is another action proceeding in the sun that may induce the earth's magnetism. The solar prominences are mighty jets of erupted matter, projected to a distance of 200,000 miles and more from the solar surface, and largely composed of dissociated water and steam. Now, we know that when a jet of steam issues forcibly from a boiler, electric disturbance occurs to such an extent that the hydro-electric machine, exhibited some years ago, produced flashes of mimic lightning, although the boiler was but a few feet in diameter. Everything surrounding such a boiler was electrically disturbed by induction, and such disturbance cannot occur without corresponding magnetic excitation. In the last chapter of "The Fuel of the Sun" I ventured to suggest that the earth's magnetism may be thus induced, and that we may thus account for the tremors of the needle that accompany every excessive solar outburst. I still cling to my own hypothesis, but do not therefore reject that of Professor Adams, for both actions may coexist and co-operate. My hypothesis explains the magnetisation of the iron vapours which Professor Adams

assumes, and his magnetised iron vapours intensity the induction which I demand, somewhat in the same way as the core of iron wire increases the intensity of the induced currents of a Rumkorff coil machine.

THE "DARWINIAN THEORY."-THE ADDRESS OF F. M. BALFOUR.

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WOULD fain continue with a commentary on all the Association addresses, but space will not permit. As it is, I am compelled to carry over to next month many notes that are already due, and must therefore leave the Association addresses, but not without a few words concerning that of F. M. Balfour to the Biology Section. The subject is the "Darwinian theory" and its developments. I use this term as a quotation, having some hesitation in adopting it, fearing that it may help to confirm a widely prevailing delusion-viz. the idea that Darwin is a theorist. He is the very opposite to what we commonly understand when we use the term "theorist." The great characteristic of his wonderfully extensive labours is patient, toilsome, indefatigable collection of facts, and scrupulous cautiousness in theorizing. I read "The Origin of Species" a year or two after its publication, and found it very heavy, on account of the overwhelming quantity of detail it contains. People who have not read it sometimes compare it with "The Vestiges of Creation." It is totally different, the latter being a speculative essay throughout, starting with a cleanly cut-out, smoothed, and polished hypothesis, and simply bringing forward all sorts of facts, and not a few fancies, to support it. This renders it far more readable than Darwin's book, and explains its popularity. I have heard a great many educated people, lay and clerical, denounce Darwin, and have asked most of them whether they had read "The Origin of Species." Without a single exception, they were compelled to answer "No," and about nineteen out of twenty had not read a single line of anything else that Darwin had written; but several had read the "Vestiges" throughout. I speak of some years ago rather than of a later period, and was not at all surprised at the answers to my rude question.

As there are so many who cannot spare the time and effort for struggling through the original work and the others that have since followed it, a readable and reliable epitome of the conclusions of Darwin and his disciples is very desirable. This is admirably supplied by the address above named, which will not bear any condensation or abridgment. I strongly recommend all who desire to acquire a fair general knowledge of the subject with the least possible

amount of work, to read this address very carefully throughout, digest it for a few weeks, and then read it again.

Speaking generally of the British Association addresses, both inaugural and sectional, I regard them as the most valuable contributions to the diffusion of scientific education that our literature can boast, and regret that they are not collected and republished separately from the other material of the reports. All who desire to follow the progress of science should read them carefully and intelligently. What I mean by reading intelligently is this: on reaching the end of every paragraph, ask yourself what that paragraph means, and stick to it until you can answer the question. If technical terms occur that you do not understand, hunt them out by means of elementary treatises, or, better than nothing, by the help of a technological dictionary.

Nine out of every ten of these discourses are worth this trouble; the few exceptions are for the most part those which are SO technical as only to interest the sectional specialists. It would not do to deal thus with ordinary literature; the unfortunate reader of the greater bulk of it would indeed be tasked to discover the meaning of each paragraph, seeing that in so many none exists, the writer merely struggling to cover a large acreage of paper with neatly rounded sentences that shall "read well," though meaning nothing. The writers of the British Association addresses have all to struggle with the difficulties of condensation; the ideas they desire to express far exceed the possibilities of the time allowed them, and therefore they use the smallest possible number of words, all of which the writer has carefully considered, and they should be similarly treated by the reader.

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AN UNSUCCESSFUL ATTEMPT AT MARTYRDOM.

ERR R. EMMERICH appears as a rival to Dr. Tanner, but not exactly an imitator. Instead of endeavouring to commit suicide by starvation, Herr Emmerich has striven to attain this object by drinking daily more than a pint of water from one of the brooks near Munich which receives sewerage of all kinds, and which he believes to include the drainage from houses wherein typhoid fever cases have occurred. He is not yet dead, and appears to suppose that his own survival disproves the multitude of melancholy facts upon which the received conclusions respecting the poisonous character of sewage water are founded.

He will probably find some disciples among the anti-vaccinators and others who fix their minds upon individual cases, and upon them build up general pathological conclusions.-John Brown's child fell ill and died after vaccination, therefore vaccination is a murderous operation. That notorious drunkard Bill Smith lived to 80 years of age, therefore drunkenness does not shorten life.

The folly of generalising upon individual cases, and setting such practically baseless conclusions against those which are founded on thousands of observations, and even against the collected experience of many generations, is obvious to all who will reflect on the complex variability of the animal organisation. Rats can live and thrive, increase and multiply in sewers, feeding exclusively on sewer garbage. Rabbits would die in a few days if similarly fed and surrounded, though both are rodents. The experiment of Dr. Emmerich merely proves that his constitution is more nearly allied to the rats than to the rabbits. The tens of thousands who are annually killed by sewage poison prove that the majority of human beings resemble the rabbits rather than the rats.

THE PERSPIRATION OF PLANTS.

LL who have revelled in the luxury of cultivating their own cabbages must have noticed the big drops of water that roll about on their leaves during even the driest weather. Being most abundant in the morning, they are generally regarded as dew-drops, but this is a mistake. They are accumulations of vegetable perspiration, but nevertheless are as pure as dew-drops.

Dr. J. W. Moll has investigated this subject and published in Amsterdam the results of his researches. In eight out of forty-two cases of different species of plants the exudation was effected by special water-pores, in four of these by the stomata, or breathingpores; in eight other cases by stomata, and in three cases it took place at portions of the leaf containing neither stomata nor special water-pores. His general conclusion is that most plants have the power of excreting water in drops from their leaves, and that the effect of this excretion is to relieve the plant from excessive injection by root pressure, which injection or over-supply of water would otherwise probably interfere with the respiration of the plant by choking the air-passages.

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THE AIR OF STOVE-HEATED ROOMS.

MONG the most inveterate of the many prejudices of Englishmen are those concerning stoves and open fireplaces. "The Englishman's fireside" is the altar of his most adored family fetish, whereon he burns his daily sacrifice of coal, and at which he worships by roasting his knees and nose, while his back is lumbagoed by exposure to the main draught of cold air that flows from door and windows to the chimney.

If his lungs were in his legs with tracheal breathing apertures at their sides like those of a caterpillar, the ventilation due to open fireplaces would be admirable, seeing that the fresh air comes in and goes out by a current running along the floor and never reaching the height of the mantelpiece.

One of the reasons for the common aversion to stoves is that formerly they were usually constructed as small iron boxes which were filled with coal, and when in full operation became red-hot. This heating was accompanied with a peculiar suffocating smell, and those who breathed the air of rooms heated by such stoves were victims of a peculiarly oppressive headache.

It was once supposed that in such cases the air was unduly dried by the stove, and vases or basins of water were accordingly placed on the top. These failing to remedy the mischief, another theory was started, viz. that the odour, &c., is produced by the singeing of those particles of fibrous and other matter which are suspended in the air and visible in a sunbeam. But Tyndall has shown us that the burning of such suspended organic matter purifies and improves the air, and even that their partial combustion or roasting is advantageous by destroying the vitality of contagion germs.

In Germany and the northern parts of Continental Europe, where the winter is so severe that, with our open fireplaces, the floor stratum of cold air would be quite intolerable, the construction and operation of stoves has occupied the attention of eminent men of science. In 1851 Pettenkofer examined the action of heated stove-plates on the air, and these investigations were followed up by Deville, Troost, Morin, and others. They proved that red-hot iron absorbs carbonic. oxide, formed by the semi-combustion of the carbon of the fuel, and that the gas thus absorbed passes through the iron and is given off from the outside of the stove. Now, this carbonic oxide which is produced when the carbon takes up one equivalent of oxygen is an active irritant poison. The carbonic acid which is formed by the