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as (p. 60) that he was informed " (which implies that he opinion that the Report under discussion was open to this did not previously know) that one of Van der Waals' papers :: criticism. As a reviewer, it was my duty to express my opinion contains an elaborate study of the molecular pressure in fluids. in all honesty, and, as I hope, in all courtesy. Again he says, “I have left the passages .. which refer to this

ARTHUR W. RÜCKER. ubject in the form in which they stood before I became acquainted with Van der Waals' work. I have not sufficiently! sulied his memoir to be able as yet to form a definite opinion

Visualized Images produced by Music. whether the difficulty. .. which is raised in Appendix E. can,

In the annexed paper, and in her own words, are related the it cannot, be satisfactorily met by Van der Waals' methods." Further, he states that he had been under the impression tones and orchestral combinations. They are so very singular,

very curious effects produced on a lady friend by certain musical .. that Laplace's views had gone entirely out of fashion so entirely outside my experience, and, withal, so inexplicable, having made, perhaps, their final appearance, about 1850." that I shall be glad if you will give them a place in your

As a matter of fact, Van der Waals adopted Laplace's views columns, in the hope that some of your readers-physiological in 1873, and his formula differs from the expression po = RT, or psychological-may be able to throw some light on them. only by the introduction of two terms, one of which is obviously

I should state that the lady is in perfect health, is very intellian additional pressure such as is deduced from Laplace's theory. from these passages in Prof. Tait's Addendum that when writing conscious that these spectral images have only a subjective existI do not think that any reader could be expected to conclude gent, an accomplished musician, and not at all, in this or any

sense, the victim of a disordered imagination. She is quite fue paper he had long known the" main features of Van der ence, though visually they have all the vividness of presentment Waal investigation." To me they seemed to mean that he had which belongs to realities. tvor previously been acquainted with Van der Waals' work, nor with his methods, nor with the facts that he studied molecular were in some way a response to stimuli sent through the auditory

At the first blush it would seem as though these apparitions pressure and adopted Laplace's ideas.

While, therefore, I willingly submit to Prof. Tait's correction perve ; but this, if any, is an imperfect explanation, since it will of the phrase that he had never heard of Van der Waals," I be noticed that occasionally these visualized pictures slightly

precede the instrument they belong to. cinnot admit that, on the evidence then before me, I did him any This fact suggests that a state of unconscious expectancy may -ulutantial injustice. 12; I very much doubt whether the distinction between the ulti- be a factor in their reproduction, but it fails entirely, I think, to

Geo. E. NEWTON. mate volume and the molecular volume can be maintained if the account for their initial appearance. Equations are treated as empirical; and even if they are not, I

25 Woodland Road, Gipsy Hill, S.E. ucaht whether the ultimate volume, as defined by Prof. Tait, has The sound of an oboe brings before me a white pyramid or any real physical meaning. The value of x when p = 0 is inde: obelisk, running into a sharp point ; the point becoming more pendent of the temperature, whether deduced from the theoretical acute if the note is acute, blunter if it is grave. The obelisk

mula to which Prof. Tait refers (p. 48), or from those of Van appears to be sharply defined and solid if the note is loud, and sier Waals or Clausius : hence it must (from this point of view) vague and vaporous if it is faint. All the notes of the 'cello, te the molecular volume. In the case of Prof. Tait's new the high notes of the bassoon, trumpet, and trombone, and the eraation, which was published after his Report was completed, low notes of the clarionet and viola, make me see a flat unat which is the only one I had not seen when I wrote the dulating ribbon of strong white fibres. review, the results when we put p = or T = 0, are such as to “The tone of the horn brings before me a succession of white how that its application to these extreme cases is not legitimate circles of regularly gradated sizes, overlapping one another. My own view is that such algebraical solutions are worth very | These circles and the ribbon float past me horizontally, but the istle, and I only discuss them because I wish to show that if we point of the obelisk seems to come at me. ximit them at all they justify my treating Prof. Tait's number as "In an orchestra, when the violins strike up, after the wind an estimate of the molecular volume.

band has been prominent for a time, I see often, but not always, (3) I cannot say that I think that Prof. Tait's reason is a shower of bright

white dust or sand, very crisp and glittering vdequate. The Royal Naval College at Greenwich has done I am taking note of the recurrence of this impression, and think Dere for our naval officers than he would have us believe, and, it is becoming more frequent, but it is not invariable like the of it were not so, the Challenger Reports are not addressed to others. members of any one profession, por intended for English-speak "I have heard a great deal of orchestral music all my life, ing scientific men alone. Their cosmopolitan character is shown but I have only noticed these effects for four or five years. They hy zle e fact that bound up in the same volume with Prof. Tait's gained gradually in frequency and clearness, and now the first Report is another by a distinguished Belgian geologist.

three are invariable. Foreigners have helped to describe the specimens which our "If I know the scoring of a piece well, the various effects Expedition collected; they will read the Reports which our experts slightly precede the instrument they belong to; only the objects Paave written. It would have required but a few minutes' work, are vague and faint till the sound begins. und a few additional lines of print, to have given the final "Sometimes, if an oboe passage has an intense and yearning realts un terms which they would have understood at a glance. , character, the white point comes so near me, and moves so

(4) The analogy is fallacious. Prof. Tait has devised a rapidly, that I think it must wound me. furula into which he introduces two quantities (age and speed), "I am very anxious to make it clear that I am not trying kich are commonly expressed with reference to different units to describe a mental state by symbols, but that I actually see of time.

the point, the fibres, and the circles. Generally they seem to 1 pointed out that he had expressed in the same formula (con- float half-way between me and the orchestra. krary to conmon usage) the same quantity (pressure) in terms of “If only one class of instruments is used, the effect does not two different units, of which one is not ordinarily used by extend beyond the opening bars : for instance, in a string many of those who will make use of his work.

quartette I only see the white sand for a moment at the begin. As to the last paragraph, I have only two remarks to make, ning; if, however, wind and stringed instruments are combined, First, that I think Prof. Tait does himself injustice in re- I see the various effects again and again in one piece.” zarding a description of apparatus devised by another, and the Planery of a blunder of the Bureau International, as two of Ire most important things in his Report. Secondly, that I

Foreign Substances attached to Crabs. ihink the imputation of motives should be banished from scientific discussions.

In your issue of December 26, 1889 (p. 176), Mr. Pascoe drew In conclusion, I wish to add that probably I should have left attention to the cases of certain crabs which are frequently found Prof. Tait's defence unanswered if he had not accused me of covered with sponges, algæ, shells, &c., and brought forward spfairness. I have no desire for any controversy, and no wish also the well-known case of the Gastropod Phorus. He at the in impago his knowledge of the theory of gases. But he will same time confessed that he could not see "where protection tergive my reminding him of the old saying, *** Noblesse oblige.' came in" in any of the cases which he cited. Mr. A. O. Walker,

classical research should not be published in a state which on the other hand (NATURE, January 30, p. 296), regards it as leads the reader to the conclusion that the author was only just obvious that the attachment of these foreign substances is a t.ecoming acquainted with facts which bear upon his work and useful adaptation for purposes of concealment. Prof. Herdman have been long before the world. As a reviewer, 1 formed the also (NATURE, February 13, P. 344) bears witness to the

“scarcely recognizable" appearance of the crab Hyas when Botrylloides Gasconia) to its back instead of sponges, a variations covered with algæ, &c. Indeed, no one who has seen one of these of habit which is very interesting in connection with the appacrabs brought up with the dredge, or has found a well-covered rently fixed habit of the Australian species.-W.G. Stenorhynchus on our own shores, can seriously doubt the usefulness of the habit in rendering the animal inconspicuous. In Stenorhynchus and Inachus the process of " dressing" with

A Key to the Royal Society Catalogue. weeds and zoophytes has been described by Bateson (Journ. “A CATALOGUER" appears to have misunderstood me u Mar. Biol. Association, vol. i. 1889, p. 213), and it is seen from two points. In the index that I propose, the beads would no his description that, as also in the cases of Dorippe, Pagurus, be numbered. Again, in forming an estimate of the size of the Dromia vulgaris, &c., the foreign substances or animals become work, I made the supposition that the 8 papers of an author attached to the body not by accident but by the act of the crabs could be grouped, not under 8, but under 3 heads themselves.

JAMES C. McCOXXEL. Now Mr. Walker, in regarding all these cases as instances of adaptation for concealment, has overlooked the fact that in two of our British species of hermit crab (Pagurus bernhardus and

A Meteor. P. prideauxii) it is the habit of the animals to prefer, and often

Last night (Monday, the 3rd), as I was crossing the U to fight for, shells which are rendered conspicuous by the attach Deer Park to Richmond, I witnessed the fight of an exception ment to them of species of Anemone, in the one case Adamsia ally fine meteor, which shone out with great brilliancy Dolce rondeletii (Sagartia parasitica), in the other Adamsia palliata. standing the presence of a bright moon, which was almost i Another British species (Pagurus cuanensis) is almost invariably the full. found inhabiting a shell enveloped in the sponge Suberites

It appeared to start from the constellation of Leo, and travellel domuncula, which is frequently of a conspicuous orange-red across the sky to the westward, vanishing some too or 159 above colour Only in the smallest species of Pagurus (e.g., P. lævis) the horizon. does the animal depend invariably upon an inconspicuous ap

The night was very quiet at the time, and I heard po repart. pearance for its safety.

T. W. BAKIL The value to the crabs of a preference for shells to which

Kew Observatory, Richmond, Surrey, March 4. Actinians are attached is found in the fact that these gaily. coloured animals are carefully shunned by fishes on account of their stinging powers; and although hermit crabs themselves THE DISCOVERY OF COAL NEAR DOVER are very palatable to fishes, their association with Actinians, while rendering them conspicuous as they move about, is at the THE

question of the existence of coal under the newer same time an efficient protection from the persecution of their attention of some of our leading geologists since the year enemies.

This also explains the habits of the two Mauritian crabs, 1855, has found its final answer in the discovery announced which, according to Möbius, carry about a sea-anemone in each last week in the daily press. The story of the discovery claw.

is a striking example of the progress of a scientific idea, The sponge with which Pagurus cuanensis is associated is (like passing through various phases, and growing more clearly all other sponges with which I have experimented) exceedingly defined through opposition and failure, until ultimately obnoxious to fishes on account of its bad smell and taste. I has been proved to be true, and likely to lead to industria have never succeeded in inducing a fish of any species to swallow changes of national importance. a fragment of the sponge ; but on the contrary the smell is in most cases quite sufficient to drive the fish away. The associa- Mr. Godwin-Austen in a memorable paper brought before

The question was originally started 35 years ago by for I know of no fish capable of extracting the crab from its the Geological Society of London, in which it was arged, retreat. It is seen from this that the case of Dromia vulgaris from the character and arrangement of the coal-fields and should probably be removed from the category of adaptations for associated rocks of Somersetshire and South Wales nn concealment, and, like the cases of P. bernhardus, &c., be in the west, and of the Belgian and North French coal-fields cluded in a special group of warning adaptations.

on the east, that similar coal-fields lie buried beneath the There yet remains the interesting case, adduced by Dr. R. von newer strata of the intervening regions. Mr. GodwinLendenfeld, of Dromia excavata associated with a Compound Austen pointed out that the general direction of the Ascidian of the genus Atopogaster (Herdman). This, I believe, exposed coal-fields was ruled by a series of great ease will be found to belong to the same category of warning adapta- and west folds, running parallel to the great line of dis tions, for after repeated experiments with Compound and other turbance_"the axis of Artois,"_from the south of Ireland, Tunicata at the Plymouth Laboratory I can state that these through South Wales and Northern Somerset on the animals are essentially inedible to fishes. The inedibility is in west, eastwards through Belgium and Northern France large part due, as in the case of sponges, to the characteristic into the valley of the Rhine, near Düsseldorf. Through odour which Tunicata, and more especially Compound Tunicata, give out, and in no family (excepting perhaps the Botryllida) out this area the exposed coal-fields lie in long east and is this better marked than in the Polyclinida, the group to which west troughs. This series of folded Carboniferous and older Atopogaster belongs. Bearing in mind also the fact that Com- rocks formed also an east and west ridge along the line posite Ascidians frequently vie with sponges and Actinians in the of the axis of Artois, which gradually sank beneath the possession of varied and conspicuous colours, it is rendered waves of the Triassic, Liassic, Oolitic, and Cretaceous practically certain that the case of Dromia excavata is another seas. Against this the strata of the three first of these instance of this same type of adventitious warning contrivances. rocks gradually thin off, while the coal-measures and

Thus the edible (the edibility is not yet proved for foreign other rocks of the ridge have repeatedly been struck in species) Crus'acea which attach foreign substances to their bodies France and Belgium, and are now being worked imme may be divided into two groups :

(a) Those which are rendered inconspicuous in relation to their diately underneath the Cretaceous strata over a wide natural surroundings by the habit ; e.g., Stenorhynchus, Hyas,

area. Dorippe, Pagurus lavis, and young forms of Pagurus bernhardus, newer rocks in the south of England, is marked frums

The axis of Artois also, where it is concealed by the &c.

(B) Those which associate themselves with animals, easily Somerset eastwards by the anticlinal of the chalk of recognizable by, and possessing qualities offensive to, their chief North Wiltshire, and the line of the North Downs, the enemies ; e.F., Dromia vulgaris and excavata, Pagurus bern general law seeming to be that when any great folding hardus, priteauxii, and cuanensis. WALTER GARSTANG. and dislocation of the earth's crust has taken place, each Laboratory of the Marine Biological Association,

subsequent disturbance follows the very same lines, and Plymouth, February 21.

that simply because they are lines of least resistance." P.S.-From facts which Mr. Weldon and Mr. Harmer have Mr. Godwin-Austen, by combining all these observa communicated to me, it would appear that Dromia vulgaris fre- tions, finally concluded that there were coal-fields

beneath quently attaches Compound Ascidians (Leptoclinum maculosum, the Oolitic and Cretaceous rocks of the south of England,

and that they were sufficiently near the surface to allow of Wealden rocks were present, they were more than of their being of great economic value. He further 1000 feet thick. specified the line of the Thames Valley, and the region For the next eleven years the problem remained where of the Weald, as possible places where they might be it was left by the results of the Netherfield boring ; while discovered.

in the district of London, evidence was being collected These important conclusions were during the next 11 | in various sinkings for water, which proved the existence years generally received by geologists, with the exception of the Palæozoic ridge of rocks, Silurian and old red of Sir Roderick Murchison. The next important step in sandstones, older than the Carboniferous, at about 1000 the direction of their verification was that taken by the feet from the surface. Here, too, the Oolitic strata were Coal Commission of 1866-67, by whom Mr. Godwin- not more than 87 feet in thickness, at their thickest point Austen and Sir R. Murchison were examined at length, in the well at Richmond. The older rocks, moreover, and the results of the inquiry embodied in the Report by were inclined at a very high angle, as in the case of the Mr. Prestwich. In the Report, Mr. Godwin-Austen's similar rocks underlying the coal-fields of Somerset, and views are accepted, and fortified by a vast number of of Northern France and Belgium, and this implied the details relating both to the coal-fields of Somersetshire existence of troughs of coal-measures in the synclinal and of France and Belgium. Mr. Prestwich also calls folds, in neighbouring areas. special attention to the physical identity of the coals of I come now to the last experiment, which has been so these two regions, and to the fact that the Carboniferous fortunately crowned with success. In 1886, I reported and older rocks in both are similarly disturbed. He con- to Sir Edward Watkin that it was desirable, both on cludes, further, that the coal-fields which now lie buried scientific and commercial grounds, for a boring to be put beneath the newer rocks are probably equal in value and down in South-East Kent, in the neighbourhood of Dover, in extent to those which are exposed in Somerset and and that the Channel Tunnel works under the ShakeSouth Wales on the west, and in Belgium and France on spear Cliff would be the best site for the experiment. It the east.

was almost within sight of Calais, where the coal-meaIn 1872 the Coal Commission Report was published, sures had been proved at a depth of 1092 feet. It was and in the same year the Sub-Wealden Exploration also not many miles away from the spot where a large Committee was organized i by Mr. Henry Willett to test mass of bituminous material—which, according to Mr. the question of the existence of coal in the Wealden area Godwin-Austen, was the result of the distillation of coal by an experimental boring. The site chosen was Nether- from the measures beneath-had been discovered in the field, near Battle, in Sussex, where the lowest rocks of the chalk. Sir Edward Watkin acted with his usual energy Wealden formation form the bottom of the valley. It on my report, and the work was begun in 1886, and was resolved to go down to the older Palæozoic strata, carried on, under my advice, down to the present time. which were thought to occur at about 1000 feet from the The boring operations have been under the direction of surface, or to carry the bore-hole to 2000 feet if they were Mr. F. Brady, the chief engineer of the South-Eastern not struck before. The work was carried on under con- Railway, to whose ability we owe the completion of the siderable difficulties for the next three years, until in 1875 work to its present point, under circumstances of great it had to be abandoned at a depth of 1905 feet, because difficulty. The strata passed through may be generalized of the breakage of many hundred feet of lining-pipes, as follows :coupled with the loss of the boring-tool at the bottom. The section of the strata passed through is as follows :

Section at Shakespear Clif, Dover.

Lower Grey Chalk, and Chalk-Marl
Netherfield Section,

Glauconitic Marl
Feet.
Gault

500. Purbeck strata

200

Neocomian
Portland strata

57

Feet.

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Portlandian
Kimmeridge Clay?

1073
Corallian rocks?

Kimmeridgean
515

Corallian ...
Oxford Clay
60

660. Oxfordian

Callovian 1905

Bathonian ... This section, although it yielded no information as to

Coal-measures, sandstones, and shales and clays, with

one seam of good blazing coal, struck at 1180 feet the Palæozoic rocks, showed that in this particular district they are more than 1900 feet beneath the surface,

from the top of the bore-hole ... and revealed the great thickness of the Kimmeridge Clay The coal-measures were struck at a depth of 1160 feet, and Corallian rocks, sufficiently distant from the ridge of or 68 feet below the point where the coal-measures were coal-measures and older rocks, against which the Oolitic met with in the boring at Calais. It may also be noted strata thin away to the north, to allow of an accumulation as a remarkable confirmation of Mr. Godwin-Austen's of Oolitic sediments to a thickness of more than 1700 feet. views as to the abrupt thinning off of the Wealden strata, In this respect, therefore, it afforded unmistakable evi- that, although along the line of the North Downs the dence that the search for the ridge in question might be Weald clay strikes towards the French coast, and is seen carried on with much greater chance of success further at low water between Hythe and Folkestone, it and the to the north, in the direction of the North Downs. The underlying Wealden strata are not represented in the great and increasing thickness of the successive newer section at the Shakespear Cliff. rocks of the Wealden formation, which form the surface It is too soon as yet to measure the full value of this of the ground between Netherfield and the North Downs, discovery near Dover, while our work is as yet unfinished. rendered it undesirable to repeat the experiment within We may, however, remark that the coal-fields of the the Wealden area proper. Close to Battle, the Secondary Continent, which have been proved beneath the newer strata were of great thickness, and where the whole series rocks in Northern France and Belgium, some 60 miles to

The Committee consisted of Profs. Ramsay and Phillips, Sir John Lub- the west of their eastern outcrops, have now been traced back. Sur Flulip Egerton, and Messrs. Thomas Hawksley, Warington across the Channel, that they are at a workable depth, Smyth, Prestwich, Bristow. Etheridge, Boyd Dawkins, and Topley, and that we have now a well-defined base for further

The precise boundary between these two groups is uncertain. If the Kammendge Clay series be taken down to the Coralline Oolite, its thickness researches in Southern England. will be 1913 fect.

W. BOYD DAWKINS.

20.

1.

Atomic

THE RELATION BETWEEN THE ATOMIC tained and the position occupied by the added metals in VOLUMES OF ELEMENTS PRESENT IN the periodic classification (Phil

. Trans. Roy. Soc., rol IRON AND THEIR INFLUENCE ON ITS clxxix. p. 339, 1888). Prof Roberts-Austen has deduced MOLECULAR STRUCTURE.

from this that an analogous relation should exist for Iron IN N a lecture on the Hardening and Tempering of Steel, but the irons and steels of commerce are such complex

published in November last (Nature, vol. xli. pp. 11, products, and the same metal may assume such different 32), an attempt was made to set forth the prominent facts aspects, that the relation in question is not readily apparen

: M. Osmond, which tend to prove that iron, like many ideas as guides, it appeared to me that the law of Robert developed in recent researches, more especially those of from a study of their mechanical properties.

“In reviewing my former experiments with these ne allotropic one.' It was shown that as a mass of iron or Austen was well based, and new experiments undertakes steel cools down, there are at least two distinct evolutions to verify it have only confirmed my first view. of heat, one occurring at a variable temperature not higher of iron I have studied experimentally with more or less

“The foreign elements whose action on the critical pointa than 855° C., the other at a more constant temperature, near 650° C.' From a long series of most patient investi completeness, are ranged as follows in two columns in the gations, Osmond argues that there are two kinds of iron, order of their atomic volumes :one [hard] B iron, and the other (soft) a iron. The

IL molecular change from B to a iron is indicated by the

Atomic volume.

volan first evolution of heat in the cooling mass of iron or steel, Carbon

36 Chromium and at this point the cooling mass of iron regains the Boron

41

Tungsten ... 96 magnetic properties which it loses at higher tempera Nickel

67

Silicon tures. The second evolution of heat only occurs in car Manganese 69

Arsenic burized iron or steel, and marks the point at which carbon Copper

71

Phosphorus 133 itself changes from the dissolved or 'hardening-car

Sulphur

157 bon,' to the state of combined or "carbide-carbon.' In highly carburized steel, the two points at which "The elements in column l., whose atomic volumes are heat is evolved coincide, and experimental evidence smaller than that of iron ('2), delay during cooling. has been given (loc. cit

. p. 34) as to the abnormal cæteris paribus, the change of B[hard) iron to a (soft) iron, molecular weakness which is exhibited when a very hot as well as that of 'hardening-carbon' (carbone de trempu'

. bar of such steel cools down to about 660°C. In a recent into 'carbide-carbon' (carbone de recuit). For the communication to NATURE (February 20, p. 369), Prof. two reasons they tend to increase, with equal rates of Carl Barus, of Washington, has pointed out, with refer- cooling, the proportion of B iron that is present in the ence to this molecular weakness, that when iron passes cooled iron or steel, and consequently the hardness of the through the temperature of recalescence its molecular metal. Indeed, their presence is equivalent to a more or condition is almost chaotic”; whilst with regard to less energetic hardening Osmond's view that a iron passes to B iron when sub “On the other hand, the elements of column II., whose mitted to any stress which produces permanent deforma- atomic volumes are greater than that of iron, tend m tion of the mass, Prof. Barus says that "there is reason raise or at least to maintain near its normal position to be urged even in favour of the extreme view” that such during cooling, the temperature at which the change of molecular change may be produced in most metals. In B to a iron takes place; further, they render the inverse the lecture at Newcastle, I expressed the belief (NATURE, change during heating more or less incomplete, and loc. cit.) that it would be shown that the influence of usually hasten the change of 'hardening-carbon' :0 small quantities of other elements on masses of iron 'carbide-carbon.'? would be found not to be at variance with the periodic "Thus they maintain the iron in the a (soft] state at high law. I had already given experimental evidence to show temperatures, and must therefore have the same effed in that the action of small quantities of impurity on the the cooled metal. In this way they would act on iron & tenacity of gold was closely in accordance with that law, annealing does, rendering it soft and malleable, did not but in the case of iron it was difficult to say what pro- their individual properties, or those of their compounds

. perty of the metal would be most affected by the added often intervene and partially mask this natural conse matter. It appeared safe, however, to point to the pos- quence of their presence. sibility that the direct connection with the periodic law “The essential part, therefore, played by foreign elemes: would " be traced by the effect of a given element in alloyed with iron, is either to hasten or delay the passant retarding or promoting the passage of ordinary iron to of iron, during cooling, to an allotropic state, and m the allotropic state," a point of much importance, as the render the change more or less incomplete in one sense mechanical properties of the metal must depend on the or the other, according to whether the atomic volume of atomic arrangement in the molecules.

the added impurity is greater or less than that of iron I am glad that so eminent an authority and admirable In other words, foreign elements of low atomic volume experimenter as M. Osmond has satisfied himself as to tend to make iron itself assume or retain the particula: the probable accuracy of this view. In two recent papers molecular form that posses-es the lowest atomic volume. communicated to the Académie des Sciences, the results whilst elements with large atomic volume produce the of his experiments are given, and the following is a inverse effect. translation of the later of these (Comptes rendus, vol. cx. “It should be noted that carbon, whilst obeying the p. 346):

general law, possesses on its own account the property of

undergoing, at a certain critical temperature, a change the “Within the last few years and quite recently (Comptes nature of which is still disputable, although its existences rendus, Séances des 26 octobre et 6 décembre 1886, 4 acknowledged. It is this property which gives carbon a avril 1887, et 3 février 1890), I have had the honour to place by itself in the metallurgy of iron." submit to the Academy facts relating to the allotropic modifications of iron, and to the part played in such M. Osmond has shown me the curves which represen! changes by foreign bodies alloyed with the mass. Prof. the results of his experiments, and these will doubtless Roberts-Austen, by studying the effect produced on the To the elements of column J. hydrogen may be added. As ie wn mechanical properties of gold by the addition of the same known, this element renders electro-deposited iron hard and faritale, peito weight (about o 2 per cent.) of seventeen foreign metals, it would be better to say with Graham hydrogenanm, for hydrogen gaan has discovered a curious relation between the results ob

not appear to have a marked influence on the antical temperamre.

Tungsten alone presents certain anomalies

soon be published. Whatever may ultimately prove to early resolved into their constituent formations by be the true nature of the molecular change which accom- Murchison, and later as completely by Sedgwick in his panies the thermal treatment of iron and determines its more difficult field. mechanical properties, there is little doubt but that there Already in March and April of 1833, Murchison showed, is a close relation between the action of foreign elements by his communications to the Geological Society of and their atomic volume. Few metallurgial questions London, that he had made great progress ; for the reare of greater interest at the present time than those port says : 2-He" separated into distinct formations, by which relate to the molecular structure of metals, and the the evidence of fossils and the order of superposition, the admirable work of M. Osmond has shown it to be very upper portion of those vast sedimentary accumulations probable that the presence of a small quantity of a foreign which had hitherto been known only under the common metal may cause a mass of another metal to pass into an terms of Transition Rocks and Grauwacke.” And these allotropic state. In relation to iron and steel the problems distinct formations” were: (1) the Upper Ludlow rocks ; are of great industrial importance, and it is fortunate (2) the Wenlock limestone ; (3) the Lower Ludlow rocks; that we appear to be nearing the discovery of a law in (4) Shelley sandstones, "which in Shropshire occupy accordance with which all metallic masses are influenced separate ridges on the south-eastern flanks of the Wrekin by “ traces." W. C. ROBERTS-AUSTEN. and the Caer Caradoc”; (5) the Black Trilobite flag

stone whose "prevailing Trilobite is the large Asaphus

Buchii, which with the associated species,” he observed, SEDGWICK AND MURCHISON: CAMBRIAN

"is never seen in any of the overlying groups”; and AND SILURIAN.1

below these, (6) Red Conglomerate sandstone and 'slaty

schist several thousand feet in thickness. ER RRONEOUS impressions have long existed among By the following January, 1834, Murchison was ready

American geologists with regard to the relations to with a further report, in which he described the “four one another, and to Cambrian and Silurian geology, of fossiliferous formations” in detail, and displayed, on a Sedgwick and Murchison. The Taconic controversy in folded table arranged in columns, their stratigraphical this country served, most unreasonably, to intensify feel order, thickness, subdivisions, localities, and characings respecting these British fellow-workers in geology, teristic organic remains.” The subdivisions of the rockand draw out harsh judgments. Now that right views on series in the memoir are as follows, commencing above : the American question have been reached, it is desirable (I.) Ludlow rocks, 2000 feet ; (II.) Wenlock and Dudley that the facts connected with the British question should rocks, 1800 feet; (III.) Horderley and May Hill rocks be understood and justly appreciated.

(afterward named Caradoc), 2500 feet; (IV.) Builth and Sedgwick and Murchison were literally fellow-workers Llandeilo flags, characterized by Asaphus Buchii, 1200 in their earlier investigations. Prof. John Phillips, in a feet; and, below these, (V.) the Longmynd and Gwasbiographical sketch of Sedgwick (NATURE, vol. vii. p. 257), taden rocks, many thousand feet thick, set down as whose intimate friendship through fifty years "he had unfossiliferous. the happiness of enjoying," speaks thus, in 1873, of their Thus far had Murchison advanced in the development joint work:

of the Silurian system by the end of his third year, "Communications on Arran and the north of Scotland, Upper and Lower Silurian strata were comprised in it, including Caithness (1828) and the Moray Firth ; others but these subdivisions were not yet announced. on Gosau and the Eastern Alps (1829-31); and still During the interval from 1831 to 1834, Sedgwick prelater, in 1837, a great memoir on the Palæozoic strata of sented to the British Association in 1832 a verbal comDevonshire and Cornwall, and another on the coeval munication on the geology of Caernarvonshire, and rocks of Belgium and North Germany, show the labours another brief report of progress in 1833. A few lines for of these intimate friends in the happiest way-the broad each are all that was published. The difficulties of the generalizations in which the Cambridge professor delighted, region were a reason for slow and cautious work. well supported by the indefatigable industry of his zealous In 1834, as first stated in the Journal of the Geological companion."

Society for the year 1852, the two geologists took an Prof. Phillips then speaks of the Cambrian and Silurian excursion together over their respective fields. Sedgwick labours “ of two of the most truly attached and mutually says (Quarterly Journal of the Geological Society, viii. helpful cultivators of geological science in England.” 152, 1852): “I then studied for the first time the Silurian

Of these Cambrian and Silurian labours it is my purpose types under the guidance of my fellow-labourer and to give here a brief history derived from the papers they friend ; and I was so struck by the clearness of the published. They were begun in 1831, without concert natural sections and the perfection of his workmanship, Sedgwick in Wales, Murchison along the Welsh and that I received, I might say, with implicit faith everything English borders.

which he then taught me." And further, the whole In September of 1831, the summer's excursions ended, Silurian system' was by its author placed above the Murchison made his first report at the first meeting of great undulating slate-rocks of South Wales.” The geothe British Association. It was illustrated by a coloured logists next went together over Sedgwick's region, and scological map representing the distribution of the * Transition Rocks," the outlying Old Red Sandstone, Werner, 10 our own, the belief was impressed on the minds of geologists that and the Carboniferous limestone (Murchison, Report of entirely dissevered them from the fossiliferous strata with which we were the British Association, i. 91, 1831).

acquainted." These " Transition Rocks" (of Werner's system), up-Sixty to seventy-five years ago it was applied by Maclure, Dewey, and Eat n,

The term "Transition" early appeared in American geological writings. turned semi-crystalline schists, slates, and other rocks, to the rocks of the laconic region and their continuation ; for these were passing down into uncrystalline, and regarded as mostly extended eastward to a region of gneisses. The study of the rocks was comnon-fossiliferous, the "agnotosoic" of the first quarter of menced; but in 1842, before careful work for the resolution of them had been the century, were the subject of Sedgwick's and Murchi- dine-like that in which

Murchison and Sedgwick were engaged—they were, son's investigations--the older of the series, as it turned

Potsdam age ; at the same time "Transition" was shoved west of the Hud. out, being included in Sedgwick's part. They were son, over rocks that were horizontal, and already resolved. Owing to this

forestalling of investigation, and partly also to inherent difficulties, the right Printed from advance sheets kindly supplied by Prof. Dana. The determination of the several formations comprised in this Tac nic or “Tranarticle appears in the current number of the American

Journal of Science. sition " region was very long delayed. Murchison says, in the introductory chapter of his "Silurian System," 2 Murchison, Proceedings of the Geol. Soc. London, i. 470, 474, 1833, in a D4 "No one (in Great Britain, before his investigations began) was aware of the existence below the Old Red Sandstone of a regular

series of deposits

paper on the sedimentary deposits of Shropshire and Herefordshire.

3 Murchison, Proc. Genl. Soc., ii. 13, 1834. The subject was also before edutaining peculiar organic remains."" From the days of De Saussure and the British Association; Report for 1834, p. 652.

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