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but as they differ in many respects from the English, pound NO is called nitrogen dioxide,” whilst CO
is arranged in accordance with the periodic system, tice. The book is well illustrated on the whole, but
calls for little comment. Much valuable space is
wasted in some cases the photographic reproductions can
elaborate constitutional formulæ, the hardly be regarded as truly illustrative. Otherwise majority of which are advanced without the slightest we have nothing but admiration for the manner in attempt at proof or criticism. When, however, the which Prof. Dimoth in this first volume has given authors do discuss such matters they are not always. effect to the aim of the new French agricultural convincing, as the following example will show :encyclopædia.
“ The possible constitution of phosphorus pentoxide:
to phosphorus the symbol ISORGANIC CHEMISTRY FOR STUDENTS.
ΡΞP Outlines of Inorganic Chemistry. By Frank Austin
EP, Gooch and Claude Frederic Walker. Pp. xxiv +514.
suggested by the specific gravity of phosphorus in (New York: The Macmillan Co.; London : Mac
vapour condition, we might conceive phosphorus pentmillan and Co., Ltd., 1903.) Price 7s. 64. net. oxide, formed by the complete oxidation of phos'HE authors say in the preface that their aim is phorus, to have a similar constitution.
" to introduce the student to chemistry by consideration of the simplest and fewest things." Their intention is laudable enough, but it may be questioned whether their plan of entering into a long discussion of " the consecutive development of the principles upon which systematic chemistry rests,” before taking up the descriptive part of the subject, is one which Of the molecular weight of phosphorus in solid concan be commended.
dition, or of phosphorus pentoxide, we have no know
ledge, so we find it convenient to represent both subThe first 233 pages of the book are entirely devoted
stances by the simplest possible equivalent symbols, to theoretical matters, and a wide range of subjects P and P205." is included. Beginning with an exposition of the outward characteristics and quantitative
We thought that the once prevalent idea of the
laws of chemical combination, the authors pass on to discuss
preferential combustion of hydrogen in hydrocarbon balanced actions, chemical equilibrium, and the phase
flames had long since been discarded; the authors rule. Then follows a short chapter on specific heats
however, still believe in it, for in discussing the and thermochemistry, after which the student is “in
luminosity of the acetylene flame they tell us that the
gas “burns from an ordinary gas jet with a flame troduced ” to atoms, molecules, ions, and electrons.
which is luminous, but very sooty from finely divided Finally an attempt is made to teach him something about the kinetic theory of gases, the properties of
free carbon, the hydrogen burning first solutions, the theory of valency, constitutional
2C,H, +0,= 2C, +2H,0.” formulæ, physical isomerism, and stereochemical rela
In short, we find much in this book which would tionships. Whatever fault the reader may have to deter us from recommending it as a clear and trust-. find with the mode of presentment in this part of the worthy exposition of chemical facts and theories. baok, he will have no reason to complain of lack of
W. A. B. variety. The authors have attempted too much, and have sacrificed clearness to the exigencies of space.
OUR BOOK SHELF. The beginner will, we fear, be confused, and the more advanced student will find the treatment of the subject
Collodion Emulsion. By Henry Oscar Klein.
95. (London: Penrose and Co., 1905.) Price 5s. inadequate and superficial.
Without attempting any detailed criticism of these The advent of gelatin plates has almost driven. theoretical chapters, which would indeed serve collodion out of the photographic world. The wet listul purpose, we may give one or two examples of collodion process has all along retained its position in what we think an unsatisfactory way of presenting
some kinds of photo-mechanical work, but collodion idea, to the beginner. In speaking of chemical
emulsions seemed to have no place left for them until changes, the authors make use of the term " factor
a few years ago their advantages for certain technical 10 denote substances which enter into reactions ”; author of this volume did a good deal towards re
purposes were insisted on, and the publishers and mus ve read of " the change of the factor mercuric introducing them into this country on a commercial usisie into the elementary products mercury and basis. Is collodion emulsion can now be purchased OX3411 by heat," and so on. Vor do we think their the author has very little to say about the preparation invention of the clumsy expression "mass-unit
of it; he only quotes two or three formulæ from other
workers. The volume must be regarded as a guide 26. ghi" of an element will at all help the student to
to the practical user of commercial emulsions. Their KT<p the idea of " atomic weight." The beginner applications in the making of ferrotypes, lantern aili probably be at a loss to understand why the com- slides, opals, and transparencies, and for photograph
ing on wood are concisely described; but the principal doubt as to the value of the researches so ably carried part of the work, and by far the most important, on by himself and others in connection with the ample deals with the colour sensitising of emulsions, and the material of Mr. Rothschild's museum at Tring, applications of such sensitised emulsions to the produc
F. A. D. tion of negatives in the many methods of dealing with Butter-making on the Farm and at the Creamery. and reproducing colour that are now in vogue.
By C. W. Walker-Tisdale and T. R. Robinson. The applications of the newer sensitisers are de- Sixth edition, revised and enlarged. Pp. 162. scribed in many scattered communications, and often with very little discrimination between the practically
(London: Office of the Dairy World, 1906.) Price
25. 6d, net, useful and the merely theoretically interesting. Mr. Klein states that he has included only those that have
We import into the United Kingdom perhaps twice passed the test of time and been found to be
as much butter as we make, and pay twenty millions thoroughly practical. It is in this that the value of yearly for it. Some, at least, of these millions would
have been saved to the agricultural industry if our the work lies, and we think that it would have been better to have restricted the volume to this aspect of
farmers and dairymen had given as much intelligent the subject. The occasional references to the under
study to the principles of butter-making as, for
instance, the Danes have done. lying scientific facts will not help the practical man,
Unfortunately, hownor would they if they were free from the errors that
ever, in such matters as the use of centrifugal creamnow disfigure them. A volume of practical instruc
separators, the employment of pure bacterial cultures
for tions is not the place for a page or two of chemical industry, we did not lead the way; we were content
starters," and the general organisation of the equations or the expression of theoretical views that have often been called in question. However, these
to follow, and that, too, with somewhat halting foot. occupy but little space, and scarcely interfere with the
steps. Even now the small butter-maker is often a use of the book as a strictly practical manual.
sad empiricist. If cleanliness, for example, is an
article of faith with him-and frequently it is notDer Gegensatz zwischen geographischer und nicht- he holds it as a dogma, not as reasoned knowledge.
geographischer Variation. By Karl Jordan. Pp. The little book under notice may help in the re59; with 73 figures in the Text. (Leipzig: W. covery of some of those lost millions. It gives an Engelmann, 1905.)
outline of approved present-day practice in butter. The present treatise affords an excellent example of making, though it does not purport to offer much in the light that may be thrown on questions of biological the way of theoretical explanation and discussion. interest by the scientific use of entomological data. Mainly it is an account of how best to conduct the Dr. Jordan here presents a valuable résumé of some operations of a small modern dairy. It is practical of the most important results of the elaborate investi- and simple; well suited for the elementary dairygation of the chitinous sex-organs of insects, more student, for the farmer's son who wishes to know particularly the Papilios and Sphingidæ, carried on something more than mere rule-of-thumb work, and by him for many years past at the zoological museum for the private maker who supplies his own houseat Tring. These researches, the detailed results of hold from his own cows. The first few pages deal which have already appeared in the pages of “Novi- with the design, construction, and equipment of the tates Zoologicæ, are of high interest, not only to dairy: Then cream is considered, and its separation entomologists, but also to all students of the methods ripening are described, after which we pass of evolution.
to the churning and subsequent operations. A number It must, however, be confessed that the author's of simple arithmetical examples are worked out to interpretations are less acceptable than his facts. illustrate various points that arise. The last thirty Starting from the position that “species " have a pages deal, briefly and in a more technical manner. real objective existence, he endeavours to show that with the operations of a fully-equipped creamery, new species could only have arisen from geographic- including "pasteurisation " and refrigerating. ally isolated variations, not from variations occurring The book does not profess to be much more than a side by side with the parent form. The main fact on useful note-book and practical guide, but as far as it which he relies is that while “individual” goes it is excellent.
C. SIMMONDS. “ seasonal ” variation of forms inhabiting the same The Deinhardt-Schlomann Series of Technical Dic. locality is never accompanied by a variation in the tionaries in Six Languages: English, German, sex-organs (with the single known exception of French, Italian, Spanish, Russian. By Kurt DeinPapilio xuthus), the diverse geographical forms of a hardt and Alfred Schlomann. Vol. i. The Machinespecies are in very many cases found to be distinct from
Elements and Tools for Working in Metal and one another in sex-organs as well as in aspect. There Wood. Together with an Appendix, edited by P. is thus a correlation in the latter case which does not Stülpnagel. Pp. 403; 823 illustrations. (London : exist in the former, and which seems to the author to Archibald Constable and Co., Ltd., 1906.) Price warrant the conclusion that these geographical forms only can occupy the position of incipient species. This volume is the first of a series intended to aid Some of the obvious objections to this view are dealt engineers and others in reading technical works in with by Dr. Jordan, others are left unnoticed.
any of the principal modern languages. Terms of A slight inaccuracy occurs on p. 177, where a
general importance only are included; they are figure of Byblia goetsius is said to represent B. classified into subjects and many are accompanied by ilithyia, while the true B. ilithyia bears the legend an explanatory sketch. Formulæ and symbols, servB. anvatara; both mistakes being repeated in the ing as they do the purpose of an international language, text. A more serious matter is the absence of any are introduced wherever possible. The translations detailed reference to Mr. G. A. K. Marshall's work have been tested in workshops and offices in the various on this genus and his remarkable discoveries in the countries represented; so the work ought to prove of genus Precis. Some special recognition of these service in reading technical literature. The convenient should have found a place, even in a treatise of pocket size of the dictionary, the systematic arrangegeneral nature like the present. It will be gathered ment of its matter, and the full alphabetical index of from what has been said that Dr. Jordan's conclusions words in each of the six languages should gain for it are open to criticism. There can, however, be no a sphere of usefulness among technical students.
LETTERS TO THE EDITOR
that pressure ; while to apply the standard that Mr. Spens
proposes, it is necessary to determine the increment in (The Editor does not hold himself responsible for opinions
volume of the solution when unit mass of solvent enters it,
and in some cases it may be necessary to obtain the espressed by his correspondents. Neither can he undertake
coefficient of compression of the solution. lo return, or to correspond with the writers of, rejected
The experimental work saved by the adoption of the manuscripts intended for this or any other part of NATURE. standard here proposed is apparent when it is remembered No notice is taken of anonymous communications.]
that, owing to the want of suitable semi-permeable mem
branes, the measurement of equilibrium pressures is conOsmotic Pressure.
fined to but a few substances dissolved in water.
The Eruption of Vesuvius. Hr startley and I had deduced (see same volume), seems to
YESTERDAY I ascended the cone of Vesuvius up to the be an opportune moment for directing the attention of
crater, being, I suppose, one of the first climbers after the physical chemists to the necessity for an agreement as to
eruption. The ascent was made from Torre Annunziata what is meant by the term osmotic pressure.
without any difficulties, but care had to be taken to avoid Mr. Spens, following Duhem, points out that the osmotic
the courses of the avalanches of stones and ashes rushpressure, defined as the difference between the pressure
ing from the cone and spreading over the slopes more than on the solvent and the pressure applied to a solution to half a mile from the foot of the cone. semp it in equilibrium with the solvent, when the two are
I estimated the new crater to have a diameter of about separated by a semi-permeable membrane, varies according
3000 feet; the bottom was not visible, but the walls could In the nressure on the solvent. He suggests using a
be seen to a depth of about 1000 feet. The inner walls definite pressure on the solvent, say its vapour pressure,
are nearly perpendicular, partly overhanging, and I saw is the standard.
pieces of the very narrow crater edge breaking down, in I would point out that, by accepting this definition, one this way still enlarging the crater. The very regular is necessarily bound to compare two solutions when they stratified construction of the crater walls was visible. The are under different conditions-not only on account of the height of the crater edge is very different from what it was different vapour pressures of different solvents, but also on
before the eruption, being greatest on the west side, and Huvunt of the different pressures on the solutions them- diminishing in irregular steps to the north and east. At selves.
the point to which I ascended the aneroid showed an The following consideration will, I think, make this elevation of 3760 feet. From this point, which was on the lear, and at the same time will suggest a more scientific southern side, the Somma was clearly visible over the lower stardard
northern edge of the crater. This shape of the crater may There seem to be two methods of examining directly
account for the fact that the showers of lapilli and other the smotic phenomena of a solution.
fragmentary products which destroyed the villages of Otta1 One, which I may call the osmotic " force" method, jano and San Giuseppe were given a direction to the north
and east over the Somma. depends essentially on the determination of the rate at which the solvent will flow through a semi permeable
The crater now closely corresponds to the descriptions
of the great crater formed in 1822, and described by Forbes frembrane into an infinite mass of solution when there is
and Scrope. From the throat of the crater I heard a nc prressure on the latter.
constant roaring, and saw that white clouds of vapour It is r-vident that if one knew the frictional resistance
filled the huge hollow, but I did not see any ejections iu per flow, the heat developed, &c., one could calculate
of stones or dust. the Isotic " force" in absolute units.
On descending I visited the points where the lava streams I would mention, in parenthesis, that Mr. Hartley and I
started from the foot of the cone. The first lava reached have made some comparative experiments in this direction
the surface on the morning of April 4 a little west of with results which were not entirely unsatisfactory.
the Casa Firenze, but it soon stopped. Another stream 121 Viother direct methods give what may be called
started from Casa Firenze, destroying the buildings, and surbrium pressures; they depend on the measurement of
flowed half the way toward Bosco-Trecase. The lava which mi pressure necessary to bring about a balance between
damaged a part of Bosco-Trecase started on April 6 a little the solution and the solvent. These equilibrium pressures lower on the slope, and divided into two parallel branches. cannot, on account of the compression of the solution, be
The quantity of lava during this eruption was on the whole mra-ured under the same conditions.
comparatively small. No lava came from the crater. The An example will, show this plainly. The equilibrium general characteristics of the eruption are the immense jarr sure between a solution of 540 grams of cane-sugar amount of volcanic ash, lapilli, and other fragmentary in the litre of solution and the solvent (water) under atmo- material ejected, and this makes the eruption of April, 1906, spheric pressure is, in round numbers, 70 atmospheres. very similar to that of the year 79 A.D. The equilibrium pressure for 750 grams in the litre is Visiting the destroyed village Ottajano on April 19, I 134 almospheres. In the actual measurements each solution
made the following curious observation. A great number has been compressed, in one case by 71 atmospheres and of the window glasses are broken, but among the others in the other by 135 atmospheres. The conditions were there are many regularly penetrated or pierced by circular theqelore not comparable.
holes one two inches in size. These holes are 1 we could measure the osmotic “ force" of these two common on the northern and eastern sides of the houses solutions as in (1) then comparable results would be as on the other sides, and they can therefore not have been @biained, for in both cases the solution and the solvent caused by the showers of lapilli, which only came from the muld be under the same pressure (gravitational).
south-west. Some people ascribed these holes to the very tp to the present, so far as I am aware, no serious heavy lightning which accompanied the fall of the lapilli, 111pts to measure the osmotic “ force have be but I am not aware that electrical discharges may produce marle, but would suggest that, pending these, the re- such effects. larriti between the vapour and osmotic pressures of a It may be of interest to note that when visiting the luon as deduced by Mr. Hartley and myself may be vclcanic vents of the Phlegrean Plain to investigate if uwul lor the purpose of comparing the osmotic pressures any kind of volcanic activity was shown in connection with 461 off-pent solutions.
the eruption of Vesuvius Í heard that the emanation of This relation gives the osmotic pressure of a solution steam from the Solfatara diminished greatly during the what it is under no pressure but its own vapour pressure. days of the strongest eruption of Vesuvius : normal conknowledge of the vapour pressure, together with the ditions set in later.
HJ. SJÖGREN. disruits of the solvent, is all that is required for calculating Naples, April 23.
of the natural ionisation and the potential gradient are In your issue of January 14, 1886 (vol. xxxiii., p. 245),
similar. Mr. T. Mackenzie reported lightning from a bank of cloud In order to discuss a possible dependency of these two to the clear sky, but, as it was quite dark, one cannot
factors, Dr. Richardson assumes that “the distribution of be certain that there were no indistinct outliers. In the earth's field reduces itself to a case very similar to Hann's “ Lehrbuch der Meteorologie (ed. 1, p. 632) that between two plane electrodes immersed in a gas and other cases of lightning from a cloud to the clear sky are
maintained at a constant difference of potential.' It is referred to.
more than questionable as to whether this assumption is On the evening of March 26, at 6.30 p.m., before dusk justifiable or not, for in atmospheric electricity we are had set in, there was a large thunder cumulo-nimbus cloud dealing with constant quantities of electricity, and not with about eight miles north of Johannesburg. The summit of constant potentials. But, rather than follow up this objecthis cloud was very sharp against a clear dark blue sky. tion, I would prefer to look at the problem from a different There was no false cirrus. Six flashes of lightning darted point of view, and show that the exact contrary conclusions from near the summit of the cloud into the clear sky. can be deduced. The longest path was about ten degrees. One Hash re- In discussing this problem, it is usual to accept that turned to the cloud, the others finished in the clear sky. there is a negative charge on the earth's surface, and Before dusk set in this phenomenon ceased to occur. All that the corresponding positive charge is a volume charge the flashes were directed to that part of the sky from which distributed in the atmosphere.
Now all the measurethe cloud moved.
ments which we have of the daily variation of potential In a well-known book on meteorology we read gradient have been made within a few metres of the suris impossible to say whether a flash of lightning moves face. Within these few metres there can be, relative to from a cloud to the earth or in an opposite direction," and the charge on the earth, very little volume charge, so further that the lightning is instantaneous. Hann does what our measurements actually refer to is the charge on not confirm these statements, and it is time that they were the surface, the relation being dv/dh=-410. The point modified in English text-books. Quite frequently I have to notice in this is that, with a given charge on the surface observed lightning flashes leaving a cloud for the earth, and the corresponding charge in the atmosphere above, the but fading away before reaching it; the opposite pheno- vertical distribution of the charge and the conducting
state of the upper atmosphere do not in the slightest affect the potential gradient within a few metres of the surface. If the potential gradient changes there it can only be by a change in the surface charge on the earth.
If there is a penetrating radiation which, besides ionising the air in closed vessels, also ionises the air in the atmosphere, we should expect from Messrs. Campbell and Wood's experiments the ionisation of the air in all parts of the atmosphere to have a daily variation. Thus the air quite near the surface would twice a day be exceptionally conducting ; one would expect that at these times there would be a greater loss of the surface charge, and so the remaining charge to be diminished, and with it the potential gradient. The consequence would be a daily variation of the potential gradient corresponding to the variation of ionisation, but the maxima of one corresponding to the minima of the other.
That such a relation does exist between the ionisation
of the lower atmosphere and potential gradient has been Fig. 1.—Lightning at Vereeniging, 1903.
shown by many observers situated in most parts of the
globe. Thus from Messrs. Campbell and Wood's results menon has not been observed. The paths of lightning
one would expect minima of the potential gradient to occur shown by photographs taken in the Transvaal all indicate
at about 8 a.m. and 10 p.m. ; this is the exact reverse of discharges from cloud to cloud, and from cloud to earth.
what really occurs. The enclosed photograph, taken by Mr. T. N. Leslie at
Thus it would appear as if Messrs. Campbell and Wood Vereeniging, is typical. Some flashes of lightning are
have added one more to the many puzzling factors coninstantaneous, the majority are not, but I do not think
nected with atmospheric electricity. any exceeds a duration of a third of a second.
GEORGE C. SIMPSON. volving wheel has been used, and shows that the duration is often certainly much longer than 1/40th of a second.
August Rainfall. Johannesburg, April 2.
R, T. A. I.
According to Greenwich experience, August has been a very dry month considerably oftener about sun-spot
maxima than about minima. This fact may be of some Diurnal Variation of Ionisation in Closed Vessels.
practical interest. UNTIL Messrs. Campbell and Wood give us some more Using Mr. Nash's table (from 1815), let us confine our definite information as to the magnitude of the daily attention to the three years about the eight maxima and variation which they have found in the natural ionisation the three about the eight minima, i.e. twenty-four years of air in closed vessels (NATURE, April 19, vol. lxxiii., in each division. p. 583), it is somewhat premature to go into a detailed The driest August in the minima division was in '55, discussion as to how this discovery will affect theories of with 1.40 inches. But in the maxima division there are atmospheric electricity. Still, the letter in NATURE of ten cases of lower values, ranging from 1.25 inches down April 26 (vol. lxxiii., p. 607) on this question from Dr. to 0.45 inch, viz. '38, 49, 59, 61, 69, '71, '82, 83, 84. O. W. Richardson calls for some remarks.
'93. Since 1837 no three-year group of this division has The facts are shortly :-(1) Messrs. Campbell and Wood been without at least one such very dry August, two have discover that the natural ionisation of air in a closed had two, and one three. vessel has a double daily period, the maxima being between The total August rainfall in those twenty-four-year 8 a.m. and 10 a.m. and between 10 p.m. and i a.m., the groups is, in the sun-spot maxima division, 50.25 inches, corresponding minima being at 2 p.m. and 4 a.m. ; (2) the in the minima division 66.50 inches, the higher value thus potential gradient in the lower atmosphere has, at most showing an excess of 16-25 inches (nearly one-third of the places, also a double period, the maxima being at about lower). 8 a.m. and 8 p.m., and the minima at about 4 a.m. and The sun-spot maximum we are now near (1905 ?) has not midday. Thus, allowing for a certain amount of un- been here considered, but I may remark that in 1904 we certainty in the exact determination of the times of the had one of those low August values (1.24 inches). maxima and minima, we may say that the daily variations
Alex. B. MacDowALL.
AT THE HEAD OF LOCH FYNE.' A
LARGER number of contributors even than
those mentioned on the title-page have conspired to make this memoir authoritative and complete. It is descriptive of Sheet 37 of the i-inch geological map of Scotland, an attractive work published in 1903, in which the north-east and southwest lines of the Caledonian earth-folding predominate, and are followed out in the trend of the intrusive masses. The memoir is illustrated by excellent plates, one of which is here reproduced; and the fact that part of the ground is familiar to the tourist gives it an additional interest.
The region described is cut, from corner to corner, by the noble inlet of Loch Fyne. The parallel reach
landscape. The fundamental rocks of the district are metamorphic, and formed a part of the Caledonian continent, on which the Old Red Sandstone gathered; and Mr. Hill points out how denudation is removing the Devonian lavas and lake-deposits in the northwest, and is revealing, in the sculpture of the old continent, a highland much like that of modern days. The ice-flows of the Glacial epoch, however, have moulded the present surface in many of its details, have left erratic blocks in quaint positions on the hills, and have deposited moraines and banks of gravel across the edges of the ancient schists.
The metamorphosed series is mainly of sedimentary origin, with many bands of limestone. The albiteschists (p. 15), which are “highly micaceous or chloritic rocks with grains or crystals of clear
FIG. 1.–The summit of the Pass of Glencroe, with Loch Restil. The rugged bill scenery is formed by the Ben Bheula schists.
From “The Geology of Mid Argyll."
of Loch Awe lies in the north-west, and Loch Eck, secondary albite,” are of special interest. Dr. Teall banked out by gravel terraces from the sea, comes in supplies an analysis, showing 3.2 per cent. of soda near Loch Long in the south-east. The traveller by and an equal amount of potash. This allows 28 per land usually enters the region by the steep and rugged | cent. of the rock to be formed of albite.
" Green fastnesses of Glencroe, and leaves it by Glen Aray, if beds,” which are hornblendic, and yet are not the he is willing to face the rain-swept moorland above intrusive epidiorites so familiar in Dalradian areas, which Cruachan towers in the north. The geological occur in a band south-east of Loch Fyne, and may surveyors, however, have become familiar with a have been derived clastically from apme preexisting
practically untrodden by any visitor. basic igneous series (p. 18). Truf walls of epidiorite Mr. Hill's appreciative introduction should be read occur, however, plentifully among the metamorphic with the aid of the hill-shaded Ordnance map,
rocks between Loch Awe and Loch Fyne. In the Sheet 37, one of the most beautiful products of a same region there are numerous later intrusions of draughtsman who surely possessed a sentiment for quartz-porphyry and other igneous rocks, probably
1. The Geology of Mid-Argyll." By J. B. Hill, with the collaboration post-Silurian in age. “Kentallenite,” described in of E X. Peach, c. T. Clough, and H. Kynaston, with petrographical detail by Mr. Hill in 1900 (Quart. Journ. Geol. Soc., tales by J.IJ. H. Teall and J. S. Flett. Pp. vi+166. Memoirs of the Geological Survey, Scouand. (Glasgow, for H.M. Stationery Office :
vol. lvi., p. 531), and first known from the Appin I Hedderwick and Sons, Ltd., 1905.) Price 8s.
promontory, occurs here and there, as a link between