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The second division of the subject is the discussion of the leading cases which have been used to prove the actual uplift and subsidence of the land, such as the raised shore-lines of Norway and northern Europe, the bored pillars of the Temple of Serapis, near Naples, the raised beaches around the Baltic, and the submerged peat bogs and forests on the British coasts. Suess examines these cases in detail, and denies that they give any evidence of secular uplift. He rejects what are generally considered some of the best established of geological truths, such as the still progressive tilting of Scandinavia. Suess denies these popular conclusions, and during his argument claims that both Lyell and Darwin mistook kitchen middens for raised sea beaches. Suess examines the evidence in detail for each case, and maintains that the inferences based on it are invalid. The shore-lines of Norway he claims to have been formed along the shores of glacierdammed lakes. The Temple of Serapis, he maintains, has no connection with secular movements, because it is actually in the breached crater of a volcano. Submerged forests, he points out, may be due to growth behind storm beaches, or on land along a low shore which has sunk by the shrinkage of an underlying water-logged bed. The raised beaches around the inner Baltic he explains by the gradual lowering of the water by the emptying of that sea. The slow emergence of the north Baltic shore is, therefore, according to Suess, the consequence of a climatic change, not of an earth movement; and Suess advances evidence to prove that the level of the southern Baltic has been constant throughout historic times.

The latter part of this volume is perhaps of most popular interest, but it is the least convincing part of the "Antlitz," and perhaps the least essential to Prof. Suess's main position. Suess admits some cases of uplift, as at the Temple of Serapis, and he admits that some of the lower Norwegian shore-lines are true sea beaches We may accept Dr. Günther's evidence showing that the uplift near Naples was somewhat wider than Suess admitted, or accept a slow uprise of the land near the great lakes of America, without rejecting the doctrine that the major changes in the range of the sea are due to changes in its level. Suess only briefly refers to the phenomenon of isostasy; and the work of Colonel Burrard in India shows that the plumb-line agrees with the pendulum as to the unequal density of the blocks in the earth's crust; and therefore some areas may have been uplifted to restore that hydrostatic equilibrium at which others are still upheld.

The second division of this volume shows that the easy inference that every submerged forest and every raised beach involves a movement of the land is not justified. Suess shows that they can be explained without any assumption of earth movements. Each case must be judged on its merits. We can accept either the explanation of a limited emergence or submergence of the land without rejecting Prof. Suess's main proposition that, in the geological past, the major changes in the range of the sea have been due to variations in its level. J. W. G.

REFUSE DESTRUCTORS.

(1) The Disposal of Municipal Refuse. By H. de B. Parsons. Pp. x+186. (New York: John Wiley and Sons; London: Chapman and Hall, Ltd., 1906.) Price 8s. 6d. net.

(2) Garbage Crematories in America. By W. M. Venable, M.S. Pp. x+200. (New York: John Wiley and Sons; London: Chapman and Hall, Ltd., 1906.) Price 8s. 6d. net.

(1) THE author has not attempted in this book to produce a treatise dealing with the designing of the details for the final disposal of city refuse, but rather to set forth clearly the principles underlying the sanitary and economic handling and destruction of such material. The book owed its origin to certain designs which Mr. Parsons was engaged upon in connection with the disposal of the refuse of the city of New York, and as a result the bulk of the appliances and plant which the author describes are those which are employed in the Empire City, and there is a number of excellent reproductions of photographs of the methods adopted in that city both for collecting and for disposing of the refuse.

In

In chapter iii. it is shown that the general refuse for which a method of collection and disposal must be provided can be divided into five classes :— (1) ashes; (2) garbage; (3) rubbish; (4) street sweepings; and (5) snow; and tables are given to show the average composition of the first four of these, and the weight which has to be collected annually a number of selected American cities; in New York the refuse varies from 2.6 lb. to 4.9 lb. per head per diem. The methods of collecting the various classes of refuse are then dealt with, and the author rightly lays stress on the absolute need of arranging the collections at regular intervals, and of the use of properly designed, covered, and water-tight carts; the important problem of cleansing streets crowded with vehicular traffic is also briefly discussed.

In the next two chapters the methods of disposal are taken up, and the various systems in use contrasted and compared; such processes as those of dumping on land or dumping in water should never be permitted; they are hopelessly insanitary; one of the illustrations—“ Disfigurement of Beach by Dumping at Sea"-is a striking instance of the abominable results which may arise from such cheap and nasty methods. Mr. Parsons is evidently of opinion that the reduction process (only applicable when the garbage is separately collected), by which oil and grease are extracted and sold, can never be made a paying process, and it seems, therefore, highly undesirable to put up plants of this nature, when they are liable to produce such serious nuisance from foul smells. It is pointed out that the incineration process, which has been such a success in the cities of England and Germany, has so far not been adopted on a large scale in the United States, but the author considers that this method is bound to become more and more common in the States; where it has been a failure it is entirely due to faulty design of the destructors, and to the desire unduly to cheapen first cost.

Undoubtedly the form of civic government in

America, with its frequent changes of administration and its too often objectionable policy of the spoils to the victors, renders such problems as the economic and sanitary disposal of city refuse much more difficult to solve than in the case of the cities of Europe, where the municipal engineering and sanitary staff have much greater influence and powers of control.

(2) Called upon to remedy defects in existing crematories in the United States, Mr. Venable has made a complete study of the principles of design of every type of crematory so far built in the States, and this book is the result. In an introductory chapter the author points out that the crudity of the methods of disposal still in use in many cities is almost incredible, and he traces much of the slow progress of reform in this matter to the frequent changes in the administrative officials. In the second chapter tables are given as to the quantities which have to be collected, and the average composition of the refuse in a few large cities; in four cities in the States the weight per head per annum ranges from 1140 lb. to 1670 lb.

In

The problem of burning refuse without offence is then taken up, and Mr. Venable insists on the absolute importance of so designing the furnace that a temperature is reached which renders the discharge of odours from the chimney stack impossible. chapter iv. the various types of crematories are divided up into classes, based on the fact that there is, or is not, some attempt at preliminary drying; each class is then described in some detail, and illustrations are given of a well-known example of each class, and lists of all the patents so far granted in the States for such crematories; the next chapter deals with the cost of working destructors, and the heat available from the products of combustion for steam raising.

In chapter vi. a complete history is given of the building of crematories in the States from 1887, the pioneer year, to the present date, and sectional drawings are reproduced of many of the furnaces which have been put up during that period. Mr. Venable is an advocate for the separate collection of garbage, refuse, and ashes, and, therefore, while quite ready to admit that the destruction of refuse in England, where usually the whole of the refuse is collected in one receptacle, is admirably carried out at the present day, he does not think that the British type of destructor is ever likely to come into extensive use in America; he, however, gives details of some of the tests carried out on Meldrum furnaces in Great Britain. In the last three chapters the materials and methods of construction likely to give the most satisfactory results are discussed, and, lastly, a draft specification is given.

These two books will be extremely interesting to English municipal authorities, because they deal fully with the methods of disposal of city refuse in the United States, methods which differ radically from those in use in our own country, and, while still convinced that we are ahead of our Transatlantic cousins in this important sanitary problem, nevertheless there is much we can learn from them.

SOME On Carbohydrate Metabolism, with an Appendix on the Assimilation of Carbohydrate into Proteid and Fat, followed by the Fundamental Principles and the Treatment of Diabetes, dialectically discussed. By Dr. F. W. Pavy, F.R.S. Pp. xi+138. (London: J. and A. Churchill, 1906.) Price 6s.

RECENT WORKS ON PHYSIOLOGY.

net.

The Dynamics of Living Matter. By Prof. Jacques
Loeb. (Columbia University Biological Series,
No. 8.) Pp. xi+233. (New York: The Columbia
University Press; London: Macmillan and Co.,
Ltd., 1906.) Price 12s. 6d. net.
Geschmack und Geruch.
berg. Pp. viii+149.
1906.) Price 4 marks.

DR.

By Dr. Wilhelm Stern(Berlin Julius Springer,

R. PAVY'S new book on carbohydrate metabolism deals with a subject to which he has devoted a long life of study and original research, and his opinions are therefore entitled to the most careful consideration and respect. He treats the subject partly from the physician's point of view, for the disease known as diabetes cannot be properly understood until the nature of the metabolism which the carbohydrates undergo in health is a matter of certain knowledge. Those acquainted with Dr. Pavy's previous writings will be aware that he has never accepted the glycogenic theory of Claude Bernard, and in the present brochure he brings forward fresh evidence of what he regards as its incorrectness. Dr. Pavy also was the first to direct attention to the glucoside nature of the proteids, and this view is also amplified. Most attention, however, will be centred on the new doctrine of absorption he puts forward, and to the important role in this process which he assigns to the lymphocytes. He supposes that what first occurs is that these cells assimilate nutrient matter and incorporate it in their protoplasm, and subsequently carry it to the tissues. Among other facts in support of this view he directs attention to the great increase in the lymphocytes of the blood after a meal. One imagines this view will not be immediately accepted, partly because it is doubtful whether the lymphocytes are sufficiently numerous, or capable of sufficiently rapid integration and disintegration to bear the burden of the large amount of material which has to be transported, and partly because the acceptance of such a theory will involve the rejection of much recent physiological work in which it has been shown that the foodproteids are broken down during digestion into the small molecules of the amino-acids of which they are composed. Dr. Pavy has produced an interesting and suggestive book, but he has made no experimental attempt to disprove the new ideas of complete hydrolysis of proteids in the intestine which are rapidly gaining credence.

Prof. Jacques Loeb's book is the outcome of a series of lectures he gave at Columbia University in 1902. He has entitled it the " Dynamics of Living Matter," and it is an attempt to explain the phenomena of life on the basis of physical chemistry. Prof. Loeb has

been an arduous worker at this branch of science, and it will be convenient to have in a compact form the outcome of his numerous fuller publications, fuller publications, which it is the object of this book to present. Prof. Loeb's name is best known in connection with tie parthenogenesis which he has artificially produced in unfertilised marine eggs, by altering the saline constituents and other physical conditions of the surrounding water. This subject is here given in its most recent developments, but the book naturally contains a good deal in addition. We may regard the work as a useful counterblast to those who term themselves neo-vitalists. It can hardly be considered the last word on the subject. Physical chemistry in relation to inorganic material is in a state of flux, one theory displacing others with startling rapidity. It is, therefore, a little early to apply it to organic and living substances with any hope of obtaining universal acceptance of the theories put forward. The speculations indulged in are interesting, and the facts will settle down into their proper places later on.

The third book in this physiological batch relates to a small corner of physiological inquiry, namely, taste and smell, and mainly the former. Dr. Sternberg has devoted attention to this sub-branch of a branch of physiology, and has produced a readable pamphlet. It is, however, a little difficult to understand why books should be written with such limited scope, and it is doubtful if they are really needed.

MATTER AND RADIO-ACTIVITY.

The Electrical Nature of Matter and Radio-activity.
By Prof. Harry C. Jones. Pp. ix+212. (London:
Archibald Constable and Co., Ltd., 1906.)
7s. 6d. net.

THIS

Price

HIS book consists of a series of articles, written in semi-popular style, reprinted from the Electrical Review. The first third of the book is occupied with the electronic theory of matter, and follows the usual popular lines. The subject is treated only from what may be called the Cavendish Laboratory point of view, and, in fact, we read that we owe the whole electronic conception to Prof. J. J. Thomson. The optical and spectroscopic foundations for the theory are omitted, and the names of Larmor, H. A. Lorentz, and Zeeman are not mentioned.

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The author, by thus presenting so dogmatically and literally the speculations which have centred around the electron as the basis of matter, has directed attention away from the solid experimental work on which our knowledge of the nature of electrons rests. It is this work, and not the sweeping electronic hypothesis, which is connected with radioactivity. But for the pioneer work on the ionisation of gases done in the Cavendish Laboratory and elsewhere, the electrical method of radio-active measurement could not have reached its present perfection. and it is safe to say that, deprived of this method, radio-activity would have advanced but slowly. But whether the atom of mercury has 200 or 150,000 electrons is a question which fortunately has nothing to do with the very fundamental and independent conclusions of the nature of matter formed from radio-active evidence.

Radio-activity, the second topic, is started in chapter v., and with the remainder of the work and the mode of treatment no exception can be taken. except that it is not very up-to-date. The last chapter, which is entitled "Most Recent Work in Radio-activity," attempts, however, to accomplish

this.

The book as a whole gives a comprehensive and interesting survey of the radio-activity of matter as it is interpreted by the disintegration hypothesis. Perhaps the best chapters are those dealing with the reproduction of radio-active matter and the theory arising therefrom. Here the chemical training and point of view of the author are in evidence, and the significance of the continuous reappearance of the products of change after complete removal by chemical or other means is very clearly brought out.

Attention may be directed to some inaccuracies and errors of minor importance. The author does not seem very clear about the nature and properties of they rays. We learn that their power to affect the photographic plate is much greater than that of the B or even the a particles, an error which is frequently repeated. Their origin is ascribed to the impact of B rays on solid matter rather than to the acceleration of the B particle during expulsion. In the experiment of causing, by means of a glass tube containing

It is difficult to attempt to review this part of the radium, a discharge to pass between two points just book, for if the reviewer has interpreted a recent paper by Prof. J. J. Thomson aright, the view that the constituent electrons of an atom are present in sufficient numbers to contribute any appreciable part of its mass appears to have been disproved. Here, however, we read :

"There is one point at least brought out so clearly that there can scarcely be any question about it, and that is that matter is a pure hypothesis."

And again ::

"The atom according to this theory is very complex. Take, for example, the atom of mercury.

so far apart that ordinarily the spark fails, most of the ionisation from the glass tube is ascribed to the 7 rays. It is safe to say that if the glass were as thick as this the experiment would fail. The statement that the emanation can be condensed at low temperatures like an ordinary gas into a liquid i obviously a slip, for a little later we read that no liquid or even mist will be seen. Twice later, however, the statement is repeated, and liquid appears a loost word for non-gaseous. The B rays are ascribed little power of exciting phosphorescence, and the effect on a platino-cyanide screen is said to be greater for = than for 8 and y rays. F. S.

OUR BOOK SHELF. Résistance, Inductance et Capacité. By M. J. Rodet. Pp. x+257. (Paris: Gauthier-Villars, 1905.) THIS book is devoted entirely to the three subjects which form the title, and it has evidently been the author's aim to include everything within the limits mentioned likely to be of use to engineers or physicists.

As a whole the author has succeeded, and has produced a valuable book of reference. The subjects are treated in the order mentioned. Under the heading of resistance, in addition to the usual constants, information is given as to the conductivities of insulators, solid and liquid, and the insulation due to a film of oil between a rotating shaft and its bearings. An account is given of the various rectifiers, including the Cooper-Hewitt.

Under the heading of inductance a full and clear statement is given of the usual phenomena, and the various methods of calculating coefficients of selfand mutual inductance are explained, but no mention is made of a rectangular coil such as is used in certain instruments of the dynamometer style. The inductance of cables is also studied, and a reference is made to the apparent increase of resistance of conductors traversed by alternating currents, but no mention is made of the internal self-induction of an iron rail, which is an important factor in the application of alternating currents to electric traction.

The initial portions of that part of the book which is devoted to the study of capacity follow the ordinary methods of exposition. Tables of specific inductive capacity of various substances are given, and information is presented as to the variation of this property with temperature. Following this, the distribution of the potential in a compound condenser is described, as, for instance, in a condenser in which the dielectric is composed of two plates of glass separated by a layer of air. (This matter is of practical importance in the building of high-voltage machines, as brought out by Messrs. Hobart and Turner in their recent book on insulating materials.) A brief reference is made to the electrodynamic condenser proposed by Mr. Swinburne, and a section is devoted to the study of capacity effects due to cables and overhead transmission lines.

The book would have been more complete if the researches of the late Dr. John Hopkinson had been referred to as to the specific inductive capacity of materials at very low temperature. For practical men, however, this volume contains almost everything that they are likely to want, and to them it can be thoroughly recommended.

Natural Phenomena. A Collection of Descriptive and Speculative Essays on some of the By-paths of Nature. By F. A. Black. Pp. xiv+366. (London and Edinburgh: Gall and Inglis, n.d.)

IN this book Mr. Black offers some essays which might well be of value to the student of physiography. Treatises on this subject are usually crammed very full of facts, and more interest might be awakened and a wider horizon opened to the student, if he reads such a work as this in connection with the ordinary text-books. There are ten essays altogether; four deal with some points connected with our own atmosphere, and four discuss problems of elementary astronomy, arising mainly from the motion of the earth on its axis. The remaining two treat of the Sargasso Sea and the Zodiacal Light with its allied phenomena. These seem to be highways rather than by-paths.

It would not be correct to say that Mr. Black is always exact in his descriptions; he is apt to be somewhat loose, and his book suggests that he has not consulted the most recent authorities. But he is never so far wrong as to be misleading. He may puzzle the student by apparent contradictions, due to the introduction or exclusion of circumstances which can exercise an important influence upon the point under consideration. Particularly would we caution the student to beware of those explanations for which the author himself is responsible, and in which he seeks to remove difficulties that have not yet received a satisfactory solution. An example will be found in the discussion on the semi-diurnal barometric inequality. The author seems, too, to have lost his way in the chapter on weather cycles; but the book is calculated to arouse interest, to stimulate curiosity, to promote further study, and on these grounds one may welcome its appearance. The illustrations are generally effective, and a very good index accompanies the book.

A Text-book of General Zoology. By Dr. Henry R. Linville and Dr. Henry A. Kelly. Pp. x+462; illustrated. (London and Boston: Ginn and Company, 1906.) Price 7s. 6d.

THIS addition to the long shelf of text-books of zoology has some fresh features. Practical experience has led the authors to begin with the Arthropods, work down to the Protozoa, and then ascend the vertebrate series. The study of insects has been found the best introduction to the broad problems of zoology, and in the earlier chapters a modified inductive method is pursued. About half-way through the book, after the student has become familiar with systems of organs, he is introduced to physiological principles, illustrated with special reference to the earthworm. Throughout the book prominence is given to the study of animal behaviour and the environmental conditions. Thus there is a feeling of fresh air through the chapters. The authors have reacted from the position of identifying zoology with comparative anatomy, and the introduction to the science which they have presented seems to us, not only interesting, but educationally wholesome. Most of the illustrations are original, and many of them are beautiful.

Science Readers. Book VII. By Vincent T. Murché. Pp. 299. (London: Macmillan and Co., Ltd., 1906.) Price is. gd.

Object Lessons in Elementary Science. Stage VII. By Vincent T. Murché. New and revised edition. Pp. xvi+322. (London: Macmillan and Co., Ltd., 1906.) Price 28.

THESE books deal with elementary physics. The first is intended for pupils to read in class, lesson by lesson, after they have attended an explanatory and experimental demonstration from the teacher on the subject in hand. The second book contains notes of lessons designed only for the use of teachers. The notes are accompanied by helpful advice, blackboard sketches, and many other evidences of the wide experience of the author. Both volumes are attractively illustrated and well printed, though it may well be doubted if the bewildering profusion of types in the second book adds to its helpfulness. The author is a master of simplicity of expression, and the information he supplies is, as a rule, trustworthy. The books deserve the careful consideration of teachers of very elementary classes.

LETTERS TO THE EDITOR.

[The Editor does not hold himself responsible for opinions expressed by his correspondents. Neither can he undertake to return, or to correspond with the writers of, rejected manuscripts intended for this or any other part of NATURE. No notice is taken of anonymous communications.]

Absorption of the Radio-active Emanations by
Charcoal.

THE interesting property of certain kinds of charcoal, notably that of the cocoa-nut, of rapidly absorbing gases, except the inert gases belonging to the argon family, is now well known since the recent experiments of Sir James Dewar.

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In a recent investigation I had occasion to pass the radium emanation through a tube filled with cocoa-nut charcoal, and was surprised to find that the emanation was completely absorbed by it. If a slow current of air, mixed with the emanation of radium, thorium, or actinium, is passed through a tube filled with charcoal, the issuing gas is completely deprived of emanation. This occurs ordinary temperatures, and there is no necessity for initial cooling of the charcoal. This property of charcoal of absorbing the radium emanation can be shown by a very simple and striking experiment. If a side tube containing a fraction of a gram of charcoal is attached to a vessel containing the emanation released from several milligrams of radium bromide, in the course of time the emanation is absorbed by the charcoal. At ordinary temperatures, several hours or days, depending on the size of the vessel, are required to effect a complete absorption as the emanation diffuses slowly through the air. If some powdered willemite is added with the charcoal, the gradual absorption of the emanation is shown by the increasing brilliancy of the phosphorescence produced in the surrounding

willemite.

It makes no difference whether the charcoal has been initially heated to get rid of the absorbed air or whether it has already absorbed its full quantity. At low pressures of the gas, using charcoal which has been previously heated, the removal of the emanation takes place rapidly. This is probably due to the rapid absorption of the gas which carries the emanation with it. The charcoal retains the emanation at ordinary temperatures, for I have found that the emanation retained in a charcoal tube open to the air loses its activity at the normal rate observed in sealed vessels.

The greater part of the emanation is released by heating the charcoal below a red heat. I have not yet settled whether the release of the emanation is due to an alteration in the absorptive power of the charcoal for the emanation at high temperatures, or whether the emanation is mechanically carried away by the rush of air which takes place when the charcoal is heated.

Since the emanations behave like inert gases of the argon family, it is somewhat surprising that charcoal should so readily absorb them. It must be remembered, however, that in ordinary experiments a very minute quantity of the emanation is present, and it is not unlikely that even the gases argon and helium are absorbed by charcoal to a small degree.

This property of charcoal of retaining the emanation promises to be of service in laboratories where radium is kept in a state of solution. It is dangerous to keep radium in the form of solution in sealed vessels, as the gradual production of hydrogen and oxygen in the solution raises the internal pressure, which would ultimately lead to the bursting of the vessel. At the same time, the escape of the emanation causes a radio-active contamination of the laboratory which renders delicate experiments on radioactivity or ionisation very difficult.

This problem will be solved by the use of a small tube containing cocoa-nut charcoal attached to the vessel, with one end open to the air. The air inside the radium vessel is kept at atmospheric pressure, while the emanation is completely stopped in the charcoal. The emanation mixed with a small quantity of gas can at any time be obtained from the charcoal by heating.

Experiments are in progress to test whether this property

of charcoal can be utilised to determine quantitatively the amount of radium emanation existing in the air, and also the amount of emanation diffusing to the atmosphere from the soil. E. RUTHERFORD.

McGill University, Montreal, October 6.

The Recent Radium Controversy.

I WAS absent from Montreal during the time of the interesting discussion on radium which appeared in the Times, and it is only quite recently that I have had an opportunity of reading the correspondence in full. In the course of this discussion some weight has been attached to a remark in the second edition of my book "Radioactivity, viz. that radium is a compound of helium and lead. It is far from my intention to reopen this discussion, on which I think quite enough has already been said, but in the last issue of NATURE (September 27) which I have just received, there appears a letter by Lord Kelvin in which this remark is still further emphasised.

Lord Kelvin quite correctly quotes my words, but I feel that the statement, apart from its context, is liable to leave erroneous impression of my views on the question especially in the minds of those who are not directly acquainted with my writings.

an

At the risk of being somewhat lengthy, I should like to quote fully some statements made in my book which, 1 think, clearly show my attitude on this question.

V. p. 482-"In order to explain the presence of helium in radium on ordinary chemical lines, it has been suggested that radium is not a true element, but a molecular compound of helium with some substance known or unknown. The helium composed gradually breaks down giving rise to the helium observed. It is at once obvious that this postulated helium compound is of a character entirely different from that of any other compound previously observed in chemistry. Weight for weight, it emits during its change an amount of energy at least one million times greater than any molecular compound known (see section 249). In addition it must be supposed that the rate of breaking up of the helium compound is independent of great ranges of temperature-a result never before observed in any molecular change. The helium compound in its breaking up must give rise to the peculiar radiations and also pass through the successive radio-active changes observed in radium.

"Thus in order to explain the production of helium and radio-activity on this view, a unique kind of molecule must be postulated-a molecule in fact which is endowed with every single property which on the disintegration theory is ascribed to the atom of the radio-elements. On the other hand, radium, as far as it has been examined, has fulfilled every test required for an element. It has a well marked and characteristic spectrum, and there is no reason to suppose that it is not an element in the ordinarily accepted sense of the term.

"On the theory that the radio-elements are undergoing atomic disintegration, the helium must be considered to be a constituent of the radium atom, or in other words, the radium atom is built up of parts, one of which, at least is the atom of helium...

P. 483 —“ Taking the view that the a particles are prjected helium atoms, we must regard the atoms of the radio-elements as compounds of some known or unknoær substance with helium. These compounds break up spontaneously, and at a very slow rate even in the case of radium. The disintegration takes place in successive stages, and at most of the stages a helium atom projected with great velocity. This disintegration is accompanied by an enormous emission of energy. The liberation of such a large amount of energy in the radioactive changes at once explains the constancy of the rate of change under the action of any of the physical and chemical agencies at our command. On this int uranium, thorium, and radium are in reality compounds of helium. The helium, however, is held in such strong combination that the compound cannot be broken up he chemical or physical forces, and, in consequence, these bodies behave as chemical elements in the ordinar l accepted chemical sense.

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