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PURE CULTIVATION OF YEAST. Courses for Beginners, as well as for Advanced Students, in Physiology and Technology of Fermentations. Biological Analysis of Yeast. The Laboratory possesses a numerous collection of Yeasts (Brewers', Distillers', Wine, Disease Yeasts), Moulds, and Bacteria. Manuals: Alfred Jörgensen, "Micro-organisms and Fermentation" (London and New York, Macmillan & Co., 1900); and "The Practical Management of Pure Yeast" (London, "The Brewing Trade Review," 1903).

The Laboratory supplies for direct use Pure Cultures of Yeast for Breweries, Distilleries, Wine Manufactories, &c., and performs Analyses of Yeasts. &c.

Further particulars on application to the Director-
ALFRED JORGENSEN. The Laboratory,
Copenhagen V. Denmark.

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CONSTITUTION and STRUCTURE of an ATOM of IODINE. (Continued from Chem. News, Oct. 11, 1907, March 18 and 24, and April 1, 1910).

Iodine has been and is being produced by the power of vegetable life in seaweed acting upon the common salt (NaCl) contained in sea-water. NaCl.

Reasons:

I

(1). Latest atomic weights of I, Na, and Cl are 126'92, 23, and 35'46. 4 x 23+ 35'46 = 127 46, or, taking C1 without its condensed protyle, 4 x 23 + 35 = 127.

(2). If iodine has been or is being formed by the union of other elements, Cl is more likely than any other element to be one of its constituents.

(3). By Deduction (J) Na is another constituent.

(4). From observed facts in mineralogy it is evident that the ultimate matrix of iodine is the sea.

(5). C1 and I are both heptads.

(6). They are isomorphous.

(7). They are similar in other respects. (N.B. This involves more than one reason).

(8). Iodine is volatile owing to its string of H-Hs, by Deduction (G). (9). It is also volatile owing to the four atoms of Na at one extremity, by Deduction (K).

(10). It is well known that in experiments with I and C1 the molecule ICls is formed when there is an excess of Cl. The action of seaweed upon four molecules of NaCl is (NaCl)Cla=ICls. It is also well known that seaweed absorbs NHa; but in order that it may form the salt NH4C1, it must take another atom of H from water, thereby forming HO-OH. This molecule, on rising to the surface, is transformed into O and H2O. The nascent O given off combines with a molecule, O2, of the atmosphere, and produces ozone.

(11). It can be shown by the theory of mathematical probability that the chance that the constitutions and structures of the elements, already given, are incorrect, is one to several thousand millions. (12). Definite constitutions could not have been obtained by reasoning upon observed facts, unless they contain the truth.

(13). From the second observation in the Chemical News, Oct. 11, 1907, it is evident that the atomic weight of I must be an odd whole number. Nitrogen was mentioned as the only exception to this rule, but it probably is not an exception, since NO is said to have been obtained.

(14). The atomic weights of the elements, as given by the International Committee, cannot yet be considered as settled, since they are continually changing. There is still the error due to condensed protyle (which has been shown experimentally to exist) to be eliminated.

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CHEMICAL NEWS, }

April 8, 1910

157

VOL. CI., No. 2628.

RECENT CONTRIBUTIONS TO THEORIES REGARDING THE INTERNAL STRUCTURE OF THE EARTH.*

By Sir THOMAS H. HOLLAND, K.T.C.E., D.Sc., F.R.S.

THE intensity and quantity of polemical literature on scientific problems generally varies inversely as the number of direct observations on which the discussions are based; the number and variety of theories in general thus form a a coefficient of ignorance. Beyond the superficial observations direct and indirect made by geologists, not extending below about one two-hundredth of the Earth's radius, we have to trust to the deductions of mathematicians for our ideas regarding the centre of the earth. They have provided us successively with every permutation and combination possible of the three physical states of matter -solid, liquid, and gaseous. Starting, say, two centuries back with the astronomer Halley, geologists were presented wtih a globe whose shell rotated at a rate different to that of its core-in recent times this idea has been re

vived by Sir F. J. Evans (1878), and by the distinguished founder of this series of lectures, to account for the secular variations of the magnetic needle. Clairault's celebrated theorem (1743), on which Laplace based the most long. lived among many cosmogonies, gave us a globe of molten matter surrounded by a solid crust. Seventy years ago Hopkins demanded a globe solid to the core, and his arguments have been in general intensified by Lord Kelvin, Sir George Darwin, Prof. Newcomb, and Dr. Rudski. But Mr. Hennessy (1886) concluded that the astronomical demands could be satisfied by the old fashioned molten

earth in which the heavier substances conformed to the

equatorial belt. Late in the seventies, Dr. Ritter started the idea of a gaseous core surrounded by a solid crust, and this was modified in 1900 by the Swedish philosopher Svante Arrhenius, whose globe with a solid crust, liquid substratum, and gaseous core is now a favourite among many geologists. Though the proportions of the layers differ, Arrhenius's globe and that of Dr. Wilde are in general agreement, and of the two the latter more nearly satisfies the simple deduction from the remarkable phenomena regarding the transmission of distant earthquake shocks noticed only four years ago by Mr. R. D. Oldham. But the variety of ideas does not end with theories on the present constitution of the globe. Poisson required the process of solidification to begin from the centre and to progress outwards, while other mathematicians had been happy with the Leibnitzian consistentior status as the first external slaggy crust. Since the days of Laplace all naturalists have been made to swallow the idea of a solar system formed by the cooling and condensation of a spheroidal gaseous nebula; and all except those geologists who have vainly searched for traces of the primeval crust have been happy in this belief. Now some American astronomers and geologists have combined to form the solar system by the aggregation of innumerable small bodies, "planetesimals," which gathered gradually into knots; thus, the earth grew gradually by accretion from quite a small body, and even now, although the process has nearly stopped, it receives much meteoric matter from outside. With this theory there must have been a time when the gravity of the earth was too small to hold an atmosphere of any but the heaviest gases, such as carbonic acid; later, it was heavy enough to retain oxygen, then

Abstract of the Wilde Lecture delivered before the Manchester Literary and Philosophical Society, March 22nd, 1910.

nitrogen and water vapour; but even now it is possibly not flying off into space. With the growth of the young globe the compression at the centre gave heat enough to melt the accumulated meteoritic matter, and the molten material reached the surface as lava, such volcanic action predominating at the surface till the atmosphere became charged with water, and the familiar processes of weathering started and formed the film of "rust which geologists know as sedimentary rocks.

With this addition to the variegated array of theories about the physical condition of the earth and its genealogy, the scientific world began to settle down again into serenity, comforted by the feeling that at any rate all agree in the fact that the earth is now a gradually cooling body, with many millions of years still before it. Then came the discovery of radium, and with it the first assurance that geologists were right in claiming a long past to be followed by a longer future than the most optimistic philosopher has dared to predict with our apparently limited store of earth-heat. Now, however, Prof. Joly warns us that if the central parts of the globe contain anything near the quantity of radium found near the surface, we may even be going in the other direction, and that instead of peaceful cooling our descendants may have to face a catastrophic heating; the now inconspicuous little body known as the earth may indeed become famous through the universe as

a new star.

Thus, we see, whole fleets of hypotheses have been launched on this sea of discussion; many of them have been decoyed by the cipher signals of the mathematician; some have foundered after bombardment by the missiles classically reserved for use by militant geologists; and others, in spite of the armour-plating of physicists, have recently been riddled by the a-rays of Rutherford. Still some survive, battered and scarred, but nevertheless seaworthy; and with these well tried craft it is proposed to examine some recently acquired information.

So far as the centre of the earth is concerned the nearest

approach to actual observation is due to recent developments of seismology. It has been shown that when a large earthquake occurs, two groups of vibrations are recorded on distant seismographs-those due to the vibrations that pass through the earth, and those that travel The vibrations that stick around by the superficial crust. to the crust travel at a fairly uniform rate of 3 kilometres, or 185 miles a second; those that pass through the earth have a greater speed, and the deeper they penetrate the earth the faster they travel. But Oldham has noticed that it the second group of vibrations enter the earth so deeply that they penetrate to within about 1600 miles of the centre, they become retarded by a core which is different in its physical characters to the rest of the earth.

It is possible that this is the gaseous core postulated by Ritter, Wilde, and Arrhenius. Oldham aptly remarks that the study of seismic waves thus promises to give us data of the kind that we now get from the spectroscope regarding the constitution of distant bodies that cannot be sampled physically.

With regard to problems nearer the crust, among the show the local variations in gravity. The remarkable work most promising results recently obtained are those which recently done in India, more especially by Colonel Burrard, has a direct bearing on geological problems regarding the state of affairs immediately below the surface; for the geodetic results can be correlated with the simple geoIn the first place, it has now logical history of the area. been shown that under the Himalayas there is a deficiency of gravity, but not so great as was assumed by Archdeacon Pratt when he framed his famous theory regarding the irregularities of the earth's surface being coincident with the variations in the mass of solid matter below.

The deficiency of gravity under the Outer Himalayas is about equivalent to 3500 feet thick of solid rock; hence at stations 8000 feet above sea-level there must be a mass of rock some 4500 feet high maintained by the rigidity of the