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THE

"The object of the present work is to give an account of the theory and practice of the dressing of minerals, which will, I hope, prove useful to the miner or metallurgist who desires to understand the principles upon which this art is based, as also to the manufacturer who supplies the necessary appliances, and above all to the student who is preparing for either of the above professions." . . . "I have disregarded the time-honoured division which would make separate branches of the dressing of ores, and the cleaning of coals."

The first impression produced on reading this statement is that the new departure is warranted; that there are many points in common in the two branches, and that the comparison of practice under the different conditions would be of an illuminating character. The further perusal of the book, however, seems hardly to bear out this promise, and the joint treatment of the two branches rather tends to confusion, for the cleaning of coal involves the use of so many methods that are inapplicable to ores and vice versa that, if the two branches are to be treated in the same book, they should at least be dealt with under different

sections.

Difficulties, inherent to the method adopted of dealing with the subject, are found throughout the book, and it is practically only in the chapter on general construction of dressing works that any clear differentiation between coal and ore dressing appears. It may be that the manufacturer should be acquainted with the machines used in both classes of work, and even that the student should acquire a knowledge of, and be able to draw comparisons between them, but that coal-miners should be called upon to study the various forms of rock-breakers, stamps, and other crushing mills and fine grinders seems unnecessary.

The book is well written and interesting, more especially, perhaps, in those parts that deal with theoretical considerations which relate to the construction of the machines. The designs of various machines are illustrated by excellent plates, and leading dimensions are often given, as well as the cost of the machines and manufacturers' figures regarding capacity. The latter are sometimes apt to be high; for instance, it is stated on p. 140 that a pair of Krom rolls 26 inches diameter by 15 inches face will crush about two tons of average ore per hour to about 30 mesh.

Relatively little information, however, is given as to setting up machines, their adjustments or running, the general conditions that have to be fulfilled or the general care of a dressing plant. Early forms of machines and historical references have received a good deal of attention, possibly more than they deserve, while in many cases modern forms have been

passed over with brief mention, and a statement that they have not been long enough in use to enable an opinion to be formed regarding their value.

The treatment of the subject is divided into general considerations; volumetric sizing; sorting and washing; comminution; separation by specific gravity; appliances depending essentially on vertical fall; jigs; horizontal current separators; shaking tables; pneumatic, magnetic, and electrostatic separation; separation by surface tension; accessory appliances and general construction of dressing works.

It is, perhaps, in the chapter on volumetric sizing that the treatment of coal and ores together is most It is sometimes difficult to gather objectionable.

screen

whether the machine spoken of is used for coal or ores, and although, of course, many of them could be used for both, there is a more or less clear line of distinction between the two. To find a Wilfley impact described between the Klein screen and Zimmer conveyor screen seems curious. Trommels are said to be satisfactory to-inch mesh. In the chapter on comminution such varying machines as rock breakers, rolls, Huntingdon mills, ball mills, tube mills, and disintegrators have been dealt with all too shortly. The Griffin mill is passed over in one paragraph, in which it is described as "like the Huntingdon mill with a single large roller which is caused to revolve on its spindle by means of gearing," but the construction, mode of action, and causes of crushing are so different in the two machines that the Griffin certainly merits a fuller description.

It seems questionable whether vanners should be included under the title of shaking tables, and no distinction is made between the condition of a pulp adapted for a vanner and that for a shaking table. The number of discussions that have taken place, and tests that have been made to prove whether it is better to classify the pulp or not before treatment on vanners, do not appear to be mentioned, while an authoritative pronouncement on the subject would have been of interest.

The subject of pneumatic separation has been treated more fully than it appears to deserve, and machines described which have certainly not warranted their existence. Magnetic separation has also received a good deal of attention, and many machines are figured which are used both for strongly and feebly magnetic substances.

In dealing with separation by surface tension, the author says it is impossible to offer correct or satisfactory explanations of the observed phenomena. He, however, presents an historical account of the development of the processes which depend upon this property, and briefly refers to several of the flotation processes. He has, however, only described the Elmore oil process and the Elmore vacuum process in any detail, from which it would seem that, in his opinion, they only are worthy of consideration. The chapter on accessory appliances passes from tipplers to various ore bin gates, then comes back to creepers, and returns to various conveyors of the belt, bucket, scraper, and screw types. Car and bucket elevators and tailings-wheels are dealt with, as well as ore

feeders, and the chapter is finished with a few words day traffic with the searching demands that motor | on weighing and sampling.

There is a great deal of varied information contained in the book, but it would have been better to confine the subject to one or other of the branches referred to in the opening paragraph.

DUSTLESS ROADS.

Dustless Roads. Tar Macadam: A Practical Treatise
for Engineers, Surveyors, and Others. By T.
Walker Smith. Pp. xi+225. (London: Charles
Griffin and Co., Ltd., 1909.) Price 10s. 6d. net.

THE

HE growing use of motor-cars, and the destructive action due to the rapid speed at which they are driven, and the sucking action of the indiarubber tyres on the surface of the roads, has rendered a change in their management necessary.

It is the almost unanimous opinion of road experts that, in order to preserve the surface of the roads in good condition, it is necessary that some kind of bituminous material must be used for binding the stones of the macadamising, which, while cementing them together, will also give a waterproof and comparatively dustless surface.

traffic makes on the surface of the road, that al bituminous binding or matrix should be employed He points out that so far, although this fact is full, recognised, no scientific study has been made standardise the materials used, and the proportion and quality of this material:

"Thus the matrix is usually prepared as it seems best to the individual in charge of the tar boiler who uses anything that comes from the local gas works: who boils it as long as he thinks necessary, and adds to it whatever he thinks may improve it in the way of pitch or creosote. It is a subject in which the personal factor has entered to an exceedingly great extent, and each man acts more or less as it seems best to him in his own mind."

The aggregates for tar macadam are also fully dealt with. The author points out that as the tar binding cements the stones together, the abrasion caused by friction in water-bound macadam is thus absent, the properties of noiselessness, elasticity, and resilience being secured. The only portion of the road material which is subject to any considerable wear is the surface, which has to bear the friction due to the rolling of the wheels, and also the impact of the horses' feet. It is, therefore, contended that the use of granite or other similar expensive material is not necessary for the lower coat, which consists of from 80 to 85 per cent. of the whole; but that where the road is only subject to moderate traffic the lower layer may consist of hard limestone or slag, either of which material holds the tar better than granite; the upper

being composed of granite. The author's experience

leads him to the conclusion

66

The book under notice has, therefore, been published at an opportune time, as the method of repairing roads described in it, which has been more or less successful, has been so far only of a tentative character, the work not being carried out on any scientific basis, but very much by the rule of thumb. The author, who was borough engineer at Barrow-layer, which has to bear the surface wear and tear. in-Furness for several years, had under his charge many miles of macadamised roads subject to motor traffic, and devoted his attention to experimenting and trying to find out the best means of solving the difficult problem of keeping these roads in good order, and preventing the creation and spreading of dust, at a reasonable outlay. The results of his experience are given in the book under notice. The author, however, not content with his own experience, has also collected the opinions of a large number of road surveyors throughout the country as to the advantages and disadvantages, and cost of tar macadam, the answers to the queries submitted being given in the tables contained in the book.

The subjects dealt with are divided into fifteen chapters relating to tar macadam as a remedy for dust nuisance; the necessity for standardisation in construction; tar; aggregates for tar macadam; preparation and laying; mechanical mixing; effect of wear and tear; scavenging, watering, and maintenance; camber, gradient, noiselessness, and hygienic advantages; tractive effort; statistics of road mileage; cost of maintenance; and tar spraying. There are twentyfour illustrations and a tabulated analysis of the replies to queries.

The author shows that the binding material used in the making or repair of macadamised roads is the crux of efficient road maintenance and the prevention of dust. His opinion is that it is absolutely necessary, if macadamised roads are to meet the needs of present

that it is an absolute waste of money to put such good material as granite in the bottom when a less costly material will do perfectly well when armoured with a good coating of tarred granite."

The patent processes known as "Tarmac " is described. The makers of this road material have expended upwards of 20,000l. in the construction of works and plants at Wolverhampton. The aggregate used is slag, the tar is distilled before using, and the mixing is done by machinery. The author, however, does not seem to think that it has any special advantage over ordinary tar macadam mixed locally when this is done in a proper manner. In the tables the cost of the materials and of mixing and laying is given for a great number of localities. As an average this may be taken as from two shillings to half a crown per square yard for a coating of 3 inches of slag and hard limestone for the bottom layer, and half an inch of tarred granite for the surface coat. The general opinion appears to be that there is a saving in the cost of maintenance of roads where tar macadam is used in place of water-bound macadam, in some cases amounting to as much as 75 per cent., the average, however, being put at 37 per cent.

With occasional tarring and sanding of the surface, a tar-macadam road, so far as the lower layer is concerned, is practically everlasting. The surface

where there is much traffic requires re-covering about once in four years. Instances are given from the author's own experience where roads having a fair amount of traffic "have been as good at the end of six years as when first covered, and so far as can be seen will need very little for another six years."

This book ought to be carefully studied by all surveyors having charge of roads subject to motor traffic.

VECTORIAL GRAPHICS.

Vectors and Vector Diagrams applied to the Alternating Current Circuit. By W. Cramp and C. F. Smith. Pp. xvi +252. (London: Longmans, Green and Co., 1909.) Price 7s. 6d. net.

[OT many years ago a certain type of journalist

sentations of important relations. Thus the complex quantity RC+iLC may be laid down as a vector in a plane, RC being the component along a chosen direction and LPC the component at right angles to this direction, while the ratio Lp/R measures the tangent of the angle between the vector and the chosen direction of reference. Again, if we regard C as a complete vector, the complex operator may be considered to be a versor rotating C through the angle just named. Can we utilise these fundamental vectorial and versorial conceptions to construct a graphical representation of real value to the electrical engineer? The answer has been given in the affirmative; and among those who have worked up the method along these lines, no one holds a higher place than C. P. Steinmetz. The method has been presented in more or less detail in most of the recent

NOT to compare and contrast the theorist and books on the alternating current, and now we have

the practical man, to the demolition of the former and the apotheosis of the latter. Fortunately, such an attitude of mind is no longer possible. The merely practical man could never have constructed the Forth Bridge, nor launched the Mauritania on her recordmaking career. Innumerable examples might be given of the necessity of true theory in the economical designing of all kinds of machinery; but probably there is nothing that better proves how much mathematical science lies at the foundation of modern methods than electrical applications, especially those that have to do with the alternating current. The whole history of the development of the transformer and the alternating-current motor is simply the realisation of the solution of a differential equation given long ago by Maxwell. In this realisation the first great steps were taken by Heaviside, who introduced the terms impedance, admittance, reluctance, &c., giving a new precision to the ideas involved. By a mathematical extension of meaning the symbols which entered into the electrical equations of steady currents became applicable to the corresponding cases of sinusoidal currents. Stated in purely mathematical language, this transition depended on the properties of the complex variable.

Thus, to take the simplest case, Ohm's law RC=E for steady electromotive force becomes Maxwell's expression (R+Ld/dt)C=E when E is variable. Representing a sinusoidal electromotive by the exponential of the imaginary ipt, we get the solution in the form (R+iLp)C=E, where C and E now stand for the amplitudes of the varying quantities. This complex quantity which operates on C may be treated analytically like the real quantity R in Ohm's law. Multiplication by the conjugate gives

(R2 + L22)C = (R − ¿Lp)E.

In the end, after all analytical transformations have been effected, the real part of the expression must be picked out. A little experience will make the average student quite efficient in this kind of algebra, especially if it is combined with numerical and practical work.

But the value of the method does not stop here. Following familiar paths, we may give a geometrical form to the expressions, and obtain graphical repre

an extremely valuable addition to the literature of the subject in "Vectors and Vector Diagrams applied to the Alternating Current Circuit," the joint work of William Cramp and Charles F. Smith, both lecturers in the electrical engineering school of Manchester University. The authors, for reasons given, depart somewhat from Steinmetz in their development of the method, but the foundation is essentially the same. Once the fundamental propositions are admitted and grasped, the whole treatment is a model of lucidity and self-consistency. One unusual feature of the book is that it assumes a certain fairly advanced knowledge at the start. This is a good feature, which might well characterise more of our text-books. The authors are careful at the same time to indicate exactly what knowledge the student must possess before he is in a position to make effective use of their methods-he must know the fundamental laws of the alternating-current circuit very thoroughly. Nevertheless, it would have been of advantage to have indicated in a few preliminary sections the manner in which the method originally took shape as a synthesis of the symbolic solutions of Maxwell's differential equations. There also seems to be a certain looseness of argument in the way in which the properties of vectors are stated. For example, having defined in the usual geometrical way the meaning of the "vector product" of two vectors, and having so named it, they remark, "This product must itself be a vector product, since it has already been shown to possess a definite sense." This is no proof, but mere statement. The defined product must be shown to obey the vector law of addition before it can be called a vector product.

These imperfections do not, however, affect the purpose of the authors, who are to be congratulated on having enriched our technical literature with a clear and systematic exposition of the vectorial graphics of alternating-current phenomena. After a discussion of the more purely geometrical character of the method, illustrated throughout by reference to familiar electrical phenomena, a succession of chapters follows on self and mutual induction, the transformer, motors of the induction type, and alternating-current commutator motors. A chapter is then thrown in on the product of two vectors, and the two concluding and longest chapters deal respectively with locus

diagrams and examples of the application of locus diagrams. The book is amply illustrated by more than a hundred diagrams. Everything is concise and to the point, and the student who works through its pages will find himself equipped with a valuable weapon of research.

THE RECONSTRUCTIONAL ANATOMY OF THE KIDNEY.

Untersuchungen über Bau und Entwickelung der Niere. Edited by Prof. Karl Peter. Erstes Heft. Inhalt I., Karl Peter, Die Nierenkanälchen des Menschen und einiger Säugetiere. II., Michio Inouye, Die Nierenkänalchen des Rindes und des Tümmlers. Pp. viii+447. (Jena: Gustav Fischer, 1909.) Price 30 marks.

THE 'HE editor of this monograph holds with Koelliker that a knowledge of the morphological characteristics of the renal tubules is an important groundwork for the study of the physiology and diseases of the kidney. This ground plan he has laid down in a bulky volume, profusely illustrated by numerous and wellexecuted drawings. By means of maceration with concentrated hydrochloric acid and subsequent isolation of the urinary tubules, as well as by reconstruction models and serial microscopic sections, he has studied, along with his pupil, Michio Inouye, the structure of the kidney in various mammalian families in great detail. For the benefit of those who desire to ascertain his results without reading the whole of the text, he condenses a summary of his work into seventy-five pages of this volume.

Prof. Peter has worked out the structure of the kidney of the mouse, rabbit, sheep, cat, man, and pig, while Inouye has studied the organ in the seal and ox. They have given a minute description, perhaps too minute, of the organ in the various animals without adding, to any great extent, to our knowledge of the subject.

As a result of his study, Prof. Peter divides the medulla of the kidney into an inner and an outer zone, and the latter into an inner and an outer area. The cortex he divides into a pars convoluta and a pars radiata. These, to some extent, can be recognised with the unaided eye or by means of a lens, and each is composed of certain definite parts of the tubules, each zone or area being composed of the same ame parts in the same species. In fact, with some slight exceptions they are composed of the same parts throughout the whole of the mammalia. A summary of the zones and their contents is given.

and

These researches of Prof. Peter-minute accurate as they are have particularly little in them that will interest those who seek to elucidate the functions and diseases of the kidneys. The author himself states that as regards the significance of the Malpighian bodies his investigations have produced nothing new. Concerning the first convoluted and zigzag tubules which he includes under the name of the Hauptstück," certain observations have been recorded with regard to variations in the amount of fat contained in the cells, and from the fact that these vary in their affinity for eosin in different parts of

66

the convoluted tubule, the deduction is made that the functions of the latter are not the same throughout its length. The facts adduced by these investigations have very little bearing on the two rival theories of the manner in which the kidney removes the urine from the blood-whether by a process of secretion or one of filtration.

The function of the narrow, clear part of the loop of Henle is concluded to be the resorption of the water which has been thrown out of the glomerulus. This is deduced from a ratio which Prof. Peter has found to exist between the relative length of this part of the tubule and the specific gravity of the urine in various mammalia with the exception of some of the smaller ruminants. In this matter his observations support the experiments of Ribbert and H. Marger, and of Hausmann. These experimenters removed the whole of one kidney and the medulla of the second in a rabbit, with the result that the urine was doubled or trebled in amount. As the narrow, clear part of the loop of Henle is contained in the medulla, it is inferred that the increase in the amount of urine is due to the removal of the resorbing part of the tubule. So many factors have to be considered in a case like this that the author's deductions must be regarded with a certain amount of reserve. While one must adinire the industry and accuracy manifested by this work, it must also be admitted that even those specially interested will find it very tedious reading, and it is to be hoped that it may be possible to confine the other promised volumes within a more modest compass. R. D. K.

THE

GREEKS AND HITTITES.

Ionia and the East. Six Lectures delivered before the University of London by D. G. Hogarth. Pp. 117. (Oxford: Clarendon Press, 1909.) Price 3s. 6d. net. CHE author of this book aims at solving the interesting problem of the origin of Hellenic civilisation in the Grecian colony of Ionia, in western Asia Minor. He utilises, in a masterly manner, the results of the extensive archæological researches that have been carried out within the last thirty years in south-eastern Europe. The excavations of Schliemann, Evans, and numerous other workers in this field have completely revolutionised our ideas about the origin of that early Grecian culture to which modern European civilisation owes so much.

Mr. Hogarth's conclusions are, that in Attica the home country of the Ionians, the population, before the migration to Asia Minor, was mainly Ægean, but mixed with a northern element of invaders from the Danubian area. At this date there survived in Attica a vigorous bloom of Egean culture affected to an unusual degree by some eastern influence, so that the colonists who settled on the west coast of Asia Minor in the early centuries of the first millennium B.C. were by no means barbarians. In Ionia the Greek settlers came in contact with a highly developed Asiatic civilisation--namely, that of the Hittites-and one of the most original features of Mr. Hogarth's book is the demonstration which he gives of the powerful influence of the Hittite civilisation in the develop

ment of the Hellenic culture in Ionia. The Hittites were predominant in Asia Minor from 2000 B.C. to Soo B.C., and, besides being possessed of a highly developed culture of their own, acted as intermediaries for the transmission of Mesopotamian culture to the Greeks. Of both these influences there is distinct evidence in the few excavations that have been carried out in Asiatic Greece.

There appears to be a rich field awaiting the archæological excavator both in Ionia and in other parts of Asia Minor. In Lydia, which was apparently a Hittite satrapy, very little excavation has been done, and in the Hittite country on the upper Euphrates hundreds of buried cities are known to exist, in some of which, it is almost certain, as Mr. Hogarth points out, bilingual inscriptions connecting the Hittite script with the Assyrian will be found. We may, then, expect discoveries equalling, if not excelling, in importance those that have recently been made in Mesopotamia, in Egypt, and in Crete.

Another iconoclastic view of Mr. Hogarth's is that the Phoenicians played an insignificant part in the development of Greek civilisation. He reduces "the part played by the Phoenicians among the Greek Isles and coasts to that of mere huckstering traders who followed seaways long ago opened by others."

Mr. Hogarth considers that the Hittites were not a maritime people, but were confined strictly to their continent by the Egean command of the sea. In view of the migration from Lydia to Umbria related by Herodotus, and of the existing population of broadheaded races in the Balkans, which, judging from its present distribution, must apparently have landed on the eastern shores of the Adriatic, Mr. Hogarth's views on the non-maritime character of the Hittites will, we venture to think, be considerably modified by future discoveries. The one weak point in Mr. Hogarth's admirable little book is his disregard of the evidence of physical anthropology. No explanation of the ethnological evolution of the East will be satisfactory which fails to account for the transition of the primitive dolichocephalic peoples of the Balkan peninsula into the strongly brachycephalic population of the present day, and in this respect Mr. Hogarth's otherwise admirable work completely fails. J. G.

SOME NEW CHEMICAL BOOKS. (1) Naturgeschichte einer Kerze von Michael Faraday. Herausgegeben von Dr. R. Meyer. Pp. viii+172. (Leipzig: Quelle und Meyer, 1909.) Price 2.50 marks.

(2) Junior Chemistry. By R. H. Adie. Pp. viii+ 266. (Cambridge: University Tutorial Press, 1909.) Price 2s. (d.

(3) Chemistry. By Prof. W. A. Tilden, F.R.S. Dent's Scientific Primers. Pp. ix + 108. (London : J. M. Dent and Co., n.d.) Price Is. net.

(1) FARADAY'S six lectures on the chemical history

of a candle were, it may be remembered, delivered to a juvenile audience at the Royal Institution during the Christmas holidays of 1860-1, nearly half a century ago.

In reading them we are impressed not merely by the

delightful simplicity and freshness of their style, and by the variety and ingenuity of the experimental illustrations, but more especially with the completeness of the story he had to tell. There is little that has been modified or extended in this branch of knowledge during these fifty years; there is scarcely a single sentence which might not be uttered without comment or correction to a similar audience to-day.

It is not surprising, therefore, that a fresh edition of Dr. Meyer's excellent German translation should be in demand among young people in Germany, and it speaks well for their appreciation of Faraday and his charming "chemical history" that the translation has reached its fifth edition.

The book is attractively bound, and contains a very pleasing portrait of the author, together with a short biography.

(2) Mr. Adie justifies the production of another elementary chemistry on the ground that the average first-year student shows a lack of intelligent understanding of chemical aims and methods, for which, we infer, the other books are mainly responsible. We are inclined to think that this want of intelligent understanding is due neither to the character of a particular book, nor altogether to the teacher, but to the kind of chemistry done in schools and fostered by the scholarship system of the older universities.

If the systematic study of chemistry at the university or college were founded on a good general knowledge of mechanics and physics, and an elementary notion of those chemical processes applicable to everyday phenomena, the path of the college professor or lecturer would be made much smoother. But schools are not content with this modest programme, and insist upon a standard of knowledge beyond the grasp of the average schoolboy. The result is that the college teacher has to build upon a muddy foundation of confused ideas, which are so familiar to examiners and so difficult to eradicate later. What commends Mr. Adie's new book is not so much the disastrous effects of its predecessors as the long teaching experience of the author. results of fifteen years' experience of a thoughtful teacher are always valuable, and, as one might have anticipated, the book offers a thoroughly sound course of practical instruction.

The

The arrangement of the exercises is clear and logical, the examples are thoroughly typical, well selected, well illustrated, and carefully described. Many of the experiments, without being exactly new, are modified and arranged in a convenient form, and the quantitative examples, which are numerous and varied, furnish a sound basis for that most difficult part of chemistry, the understanding of quantitative laws and the theories drawn from them. In reference to the quantitative part, it would be interesting to know what sort of errors the author obtained in determining such things as the gravimetric composition of water, the weight of steam, and the analysis of the oxides of nitrogen, of which no actual examples are given. If the two oxides of nitrogen give anything like correct results by the method described, that much-quoted example of multiple proportion would lose something of its elusive character.

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