the autograph of St. Luke. The details of the investigation will be found, with many other points of interest to New-Testament students, in the article above referred to.

INFLUENCE OF MAGNETISM ON CHEMICAL ACTION.1

2

MORE than a year ago I gave an account of some experiments which I had performed with the object of determining whether magnetism exerts any influence on chemical action. I succeeded in getting what appears to me to be strong evidence in favor of the view that magnetism does, at least in one case, exert a marked influence on chemical action. The principal experiment upon which this conclusion is based may be briefly described here. A vessel made of thin iron (ferrotype-plates were used) was placed on the poles of a magnet, and a solution of sulphate of copper poured into it. Instead of getting a uniform deposit of copper on the bottom of the vessel, the metal was deposited in distinctly marked lines, the direction of which was at right angles to the lines of magnetic force. Further, directly over the poles, the deposit was uniform; and this uniform deposit was bounded by a band of no deposit, from one-sixteenth to one-eighth of an inch in width.

Since the first paper on this subject was published, I have spent a great deal of time in endeavoring to discover other cases of similar action, and to extend the observations in various directions, in the hope of reaching a satisfactory explanation of the phenomenon described. I shall soon give a full account of the work in the American chemical journal. In the mean time a condensed account is here given.

I should say at the outset, that the subject of this paper has frequently been discussed and experimented upon in past years. In 1847 Wartmann summed up what had been done previous to that time, and also described some new experiments of his own. According to him, magnetism does not influence chemical action. His proof was furnished by two experiments. In the first, the electrolysis of water was carried on in a magnetic field, and the results compared with those obtained with the same apparatus without the magnet. The results were the same in both cases. In the second experiment, iron cylinders were placed

1 Abstract of a paper read before the National academy of sciences, at its semi-annual meeting in New York, Nov. 14–17, 1882.

2 American chemical journal, iii. 157. Philosophical magazine, 1847 [3], 30.

in a solution of copper sulphate. Some of the cylinders were magnetized, and others were not. No difference was observed between the deposits formed. The author calls attention

to the fact that his conclusion, that magnetism does not influence chemical action, differs from that of a number of earlier writers, among whom may be mentioned Schweigger, Döbereiner, Fresnel, Ampère, and Robert Hunt; but that, on the other hand, it agrees with that of Otto-Linné Erdmann, Berzelius, and the Chevalier Nobili.

Among the experiments referred to by Wartmann, those of Robert Hunt1 are perhaps the most striking; and to these I turned my attention. Hunt states, that, when a concentrated solution of silver nitrate or of mercurous nitrate is placed on glass over the poles of a magnet, the salts crystallize out in curious lines, of which an illustration is given. While these experiments have no direct bearing on the question whether magnetism influences chemical action or not, I nevertheless repeated them. To my surprise, the effects described by Hunt were not obtained. The conditions were repeatedly changed, the strength of the solutions, the strength and form of the magnets, the thickness of the glass plates, being varied; but under no conditions were the expected effects obtained. Some of the other experiments of Hunt were also repeated, but only with negative results. So that even the most positive statements of Hunt will require verification before they can be accepted in favor of his conclusion that magnetism influences chemical action and crystallization.

Among the experiments which I have performed since the publication of the first paper already referred to, may be mentioned the following: 1. The action of copper on zinc. In this case the magnet evidently exerted some influence on the action; causing apparently an accumulation of copper on the lines bounding the space directly above the poles. No lines between the poles like those obtained when copper acts on iron were observed. I am unable to say positively whether the faint figure observed in the zinc was due to an increased deposit of copper or to a lack of deposit. 2. Action of silver on zinc. Indistinct lines were observed, which appeared to be at right angles to the lines of force. These were obtained only when the solution of silver nitrate was quite dilute. 3. Action of copper on tin. The action was evidently modified by the presence of the magnet. 4. Action of silver on lead. No action was 1 Philosophical magazine, 1846 [3], 281.

observed. 5. Action of silver on iron. A slight effect was produced.

This

It will thus be seen, that the first experiment described is the one which best exhibits the influence of the magnet. The question still remains, whether the striking effect observed is due to the influence of magnetism on the chemical action, or to some indirect influence of the magnet. An examination of the liquid while the action is going on shows clearly that there are currents in it. Small particles of dust, or any light material, on the surface of the liquid, are drawn towards the poles, and then move in circles above the poles, to the right above one, to the left above the other. We have hence electric currents in the liquid; and these revolve under the influence of the magnet, as we would expect them to. action gives rise to a streaky condition of the liquid, and this may possibly account for the deposition of copper in the peculiar lines which have been described. I am unable to say whether this satisfactorily accounts for the fact, that the lines of deposit are at right angles to the lines of force; but, as far as I have been able to determine, it does not. Further, if the presence of the currents is the cause of the peculiar deposit of copper on iron, it would appear that the same kind of action should be observed whenever one metal is deposited upon another under the influence of a magnet. This, however, is not the case, as was pointed out above. The fact that the action takes place markedly in the case of iron, and only very slightly, if at all, with other metals, suggests, though it does not prove, that the action is in some way connected with the magnetized condition of the iron. Up to the present I have been unable to experiment with cobalt and nickel. Using nickel-plated brass, I did not succeed in getting any displacement of other metals from solutions by nickel in this condition. Experiments with these metals will of course be of special interest. If it can be shown that with them the same kind of action takes place as with iron, and that with nonmagnetic metals it does not take place, the influence of magnetism directly on the chemical action would be practically demonstrated. The slight effects observed with other metals already described may possibly be attributed to the presence of small quantities of iron in the metals experimented upon.

Turning from the ridges of copper deposited on the iron, what is the cause of the space around the outline of each pole upon which no copper is deposited? It is sharply defined; and at the end of the operation it is bright,

having remained entirely unaffected by the solution of copper sulphate. Here is evidently a region, not by any means inconsiderable, in which no chemical action has taken place. This can hardly be ascribed to the presence of currents in the liquid. The cause must, I think, be looked for in the magnetized condition of the iron; and I venture, though with misgivings, to suggest, that, the influence of the magnetism being most strongly felt in the iron at the outlines of the poles, these parts of the iron resist the action of the copper sulphate. We may imagine, that the molecules of iron in the regions immediately surrounding the poles are held more firmly than those which are less directly under the influence of the magnet, and that the interference with their motion protects them. Just as, in general, any cause which facilitates the motion of molecules facilitates chemical action, so, also, any cause which interferes with the motion of molecules would probably prevent chemical action either completely or partially. I recognize the crudeness of this suggestion. If there are any objections which can be raised against it, I shall be glad to be informed of them. In the mean time it may at least serve as a working hypothesis, and may lead eventually to a more satisfactory view. I intend to continue experiments on the subject under consideration. Unfortunately, the phenomena which can aid in the solution of the problem appear to be but few, and these do not readily lend themselves to quantitative treatment. The work will necessarily advance slowly, but I shall continue it as long as there appears to be any hope of getting results of value. IRA REMSEN.

ROTIFERA WITHOUT ROTARY ORGANS. PROFESSOR JOSEPH LEIDY, in a paper recently published in the Proceedings of the Academy of natural sciences of Philadelphia, observes that the Rotifera, or wheel-animalcules, form a small class, abundant in kind, and found almost everywhere in association with algae and with infusorians to which they were formerly considered to belong. Later they were regarded as crustaceans, but now are looked upon as belonging to the group of worms. Their usual striking characteristic, the rotary disks, is not possessed by any well-marked crustacean. Among the Rotifera, however, there appear to be some which do not possess the rotary organs, and yet in all other respects conform in structure to ordinary forms.

Dujardin, Gosse, and Claparede have described rotifers which they regarded as destitute of rotary organs: but Cohn described one with these organs, otherwise resembling the form of Dujardin, and suspects that the latter made a mistake; and remarks that the existence of a rotifer without vibratile cilia would be an abnormal condition in the class. While the forms described by the three authors above named are open to the suspicion that they may possess rotary organs which were withdrawn at the time of

their observation, there can be no question that there are others which are entirely destitute of them, and have efficient substitutes. Of this character is Dictyophora vorax, discovered by Professor Leidy in 1857. The animal is oval, transparent, and fixed in its position. The interior exhibits the usual structure of rotifers, together with the powerful muscular pharynx armed with jaws, observed to be in frequent motion. From the truncated extremity of the body the animal projects a capacious delicate membranous cup more than half the size of the body. The cup is a substitute for the rotary disks of ordinary rotifers, and is used as a net to catch food. At will it is entirely withdrawn into the body with its prey. The animal feeds on smaller animalcules; and in one instance upwards of fifty of these, mostly entomostracans, were squeezed from the stomach. With extended net, the animal measures up to 1 mm. in length. It was found in the Schuylkill River, attached to stones and aquatic plants, and also was observed attached to the sides of an aquarium.

Mecznikow, in 1866, described a similar rotifer under the name of Apsilus lentiformis, found at Giessen, attached to the leaves of the Nymphaea lutea. It especially differs from Dictyophora in the possession of bristled tentacles, and a ganglion to the pouch. Recently, also, Mr. S. A. Forbes of Normal, Ill., has described a similar rotifer with the name of Cupelopagus bucinedax; but this Professor Leidy suspects to be the same as the Dictyophora.

Later Professor Leidy has discovered another remarkable form, which he has named, from the absence of rotary organs, and its restless habit, Acyclus inquietus. It was found attached to the stems of Plumatella, a ciliated polyp, on stones in the Schuylkill River. It was always single, enclosed in profuse bunches of the familiar rotifer Megalotrocha, from which it was rendered conspicuous by its larger size, resembling a giant in a crowd. For the most part, in general structure it resembles Megalotrocha; but as a substitute for the rotary disks of the latter, it possesses a large cup-like head prolonged at the mouth into an incurved beak. The cup is retractile and protrusile, contractile and expansile. When protruded and expanded, the mouth gapes widely, and the beak becomes more extended, but always remains incurved. The animal bends incessantly in all directions, and it contracts and elongates in accord with its surrounding associates. It frequently bends, almost doubling on itself, so as to bring its prehensile mouth within the play of the currents produced by the rotary disks of the Megalotrochae, while the mouth expands and contracts so as to grasp a portion of the food brought within its reach. The movements of the animal are somewhat of a grotesque character, and reminded the author of a zealous demagogue addressing a crowd, obsequiously bowing, and greedily accepting contributions. The length of Acyclus is up to 1.5 mm. in length. The embryo at the time of its escape from the egg is a worm-like body, having the mouth furnished with vibratile cilia.

The original paper is furnished with illustrations representing both Dictyophora and Acyclus.

In one instance Professor Leidy remarks, that he had the opportunity of seeing an individual of Plumatella, with outspread arms, and in its immediate vicinity a group of Megalotrochae with open disks and an Acyclus in its midst, together with two worms of the genus Dero, with extended and expanded branchial tails, all acting together in concert, apparently perfectly regardless of the presence of one another, messmates partaking of the same repast.

RHYTHMIC MUSCULAR CONTRAC

TIONS.

CONTINUING those researches on the physiology of the contractile tissues to which we owe so much, Engelmann has lately been at work (Pflüger's archiv, xxix. 1882) on the arterial bulb of the frog's heart; selecting it as a muscular organ which contracts rhythmically on stimulation. Preliminary careful study with the aid of some of his pupils confirmed the result of all previous workers, that the bulb contains no nerve-cells. Löwit, however, just as Engelmann had finished his work, described a 'bulbus ganglion: this led to a fresh histological examination, also fruitless, so that Engelmann finally asked Löwit to send him some of his preparations. These were received and examined. Engelmann unhesitatingly asserts that the supposed nerve-cells are nothing but endothelial elements and connective tissue corpuscles. The isolated arterial bulb is accordingly nothing but a mass of muscular, connective, and epithelial tissues; nevertheless, when filled with blood serum under a suitable pressure, it, like the apex of the ventricle, executes slow rhythmic pulsations. These cease in ten or fifteen minutes, but after a while recommence, and may continue for hours. A single sudden stimulus of moderate strength applied in any pause between two pulsations calls forth, not as in the case of the ventricle a single contraction, but a rhythmic series of such. A weaker stimulus leads to only one beat, or none. Any part of the musculature of the bulb has this property, even pieces cut off and so minute as to need a lens for their observation. It is therefore undoubtedly a property of the muscle elements themselves. The muscle is also conductive: a stimulus applied to a portion united only by a narrow uncut strand with another portion, will arouse contractions in the latter. The stronger the stimulus, up to a maximum limit, the greater the number of pulsations in the series which follows its application, and the less the intervals between the individual contractions of the series. The influence of successive stimuli at not too short (3-5) intervals is like that observed by Bowditch on the ventricular apex. After long rest, irritability and contractility are diminished; if then equal successive stimuli be applied, of such strength that each only arouses one beat, each beat is more powerful than that which preceded it, until a maximum is reached; at the same time a weaker stimulus than that required at the end of the period of rest becomes sufficient to excite a contraction. Each pulsation nevertheless temporarily exhausts the muscle; if the stimuli follow at less than 2 intervals, the successive results are smaller. The contraction is always maximal for the given condition of the muscle: a strong stimulus causes no more powerful contraction than a weak, provided the latter acts at all. As in other muscles, a stimulus in itself too weak to cause a contraction makes the organ more sensitive to succeeding stimuli. As a result of this, rapidly repeated (tetanizing) stimuli at first too feeble to influence the bulb may after a time make it give an occasional beat, and ultimately cause rhythmic pulsations: that is, practically continuous stimulation gives rise not to continuous but to periodic contraction. These experiments go far in support of the view which has been gaining ground for some time back, that the rhythm of the heart's action is due not to intermittence in the stimulation sent from its ganglia to its muscle fibres, but to a property of the cardiac muscle tissue itself. The paper also contains interesting experiments on the influence of warmth and cold, and of varied

1

pressure of its contents, upon the isolated arterial bulb. The most striking temperature observation is, that the bulb, when brought to heat-standstill at or a little above 40° C., will nearly always beat again if the temperature be still raised two or three degrees. H. NEWELL MARTIN.

LETTERS TO THE EDITOR..

Algae and spray markings. INCIDENTAL to a note in Nature (xxvii. 46) on Invertebrate casts versus algae in paleozoic strata, the writer would call attention to the fact, that he has seen many track-like markings made by dried seaweeds blown along the shore. In some cases a series of parallel indentations, as if some animal had walked along, were made by the stiff projections of the rolling plant. These algae tracks and markings are very similar to many fossil tracks which have been figured. Forms similar if not identical with those described by Billings as Arenicolites spiralis from St. John's, Newfoundland, have been seen by the writer to be formed on the beach by the spray. This was especially observed last autumn at Marblehead Neck. The spray dashing over a projecting rock, and falling on the wet sands left by the retreating tide, produced a series of drop and ring like markings in the sand, varying in size from minute drops to those one or two inches in diameter. This corresponds, as regards size, with the specimens of Arenicolites collected by the writer at the Newfoundland locality. The common form of the larger spray markings is that of a ring, with a raised centre and a depressed border, surrounded by the displaced sand. The appearance is as if the drop fell like a partly closed bell of a jelly-fish, and then expanded outward in every direction, carrying the sand with it, but leaving the central portion untouched. These forms would probably be somewhat modified by the next tide, causing variations in the structure, if not obliterating the forms for the most part. As in Newfoundland, so on this modern beach, the impressions are seen crowded together, as well as singly. (See Can. nat., (2), vi. 478; Geol. survey Canada, pal. foss., ii. 77; Amer. journ. sc., (3), iii. 223.) M. E. WADSWORTH. Cambridge, Mass., Jan. 9, 1883.

Geology of Lake Superior.

I am pleased to learn from a communication published in your number of Feb. 9, and signed A. R. C. Selwyn, that the present head of the Geological survey of Canada has arrived at conclusions with regard to the geology of the Lake-Superior region precisely similar to those reached and published by Foster and Whitney over thirty years ago.

That it would have been well for the Canada survey, and for geological science generally, if more attention had been paid by Mr. Logan and his assistants to the results of the survey carried on along the south shore of the lake by the U.S. geologists, during the years 1848 to 1850, will, it is thought, become apparent to every geologist who reads a work prepared by Dr. Wadsworth and myself, soon to appear in the bulletin of the Museum of comparative zoölogy, and entitled 'The azoic system and its subdivisions.' J. D. WHITNEY.

Cambridge, Feb. 12, 1883.

Rock disintegration in hot, moist climates. Some remarks of Nordenskiöld, in his 'Voyage of the Vega,' pp. 707-713, relating to precious stones, suggest the thought that the marked differences which occur as to the manner and rate of the weathering of granitic rocks at the north and at the south

can hardly be so familiar to European scientific men as they are to American observers. At the south it is common enough to find soils that have been formed ' in place,' from the thorough and deep-seated chemical decomposition of the rocks on which they rest; while at the north, well-marked disintegration of this sort is rarely met with, even in places where the observer is not perplexed and confused by the mechanical results of glacial action. The subject has often been alluded to by American geologists, working in our southern states, notably by Professors Kerr of North Carolina, and Stubbs of Alabama, who have expressed themselves in the following terms: Speaking of the geologic formation which, "after hugging the east side of the Appalachian chain of mountains and forming some of the most valuable farming lands of the Atlantic states, enters the central eastern part of Alabama," Professor Stubbs says, "The rocks which by disintegration have given the soils of this section are mainly granites, gneisses, feldspars, hornblendes, mica-schists, etc.; and much the greater part of the section is covered by soils which have resulted from disintegration of the above-mentioned rocks in situ. And here I may remark a notable feature of these soils, -a feature which cannot fail to arrest the attention of every northern geologist: viz., that decomposition of these rocks in southern latitudes has proceeded much farther than with the same rocks in higher latitudes, and therefore has given us deeper soils. It is difficult to find in the north a soil over a few feet deep; while here it is not uncommon to find in railroad-cuts, wells, etc., disintegrated strata to the depth of thirty, fifty, or even seventy-five feet. This can be accounted for to a large extent by climatic influences. The warm waters, charged with carbon dioxide, percolating throughout the year the easily permeable strata, act continuously as a chemical agent in the work of disintegration; while farther north not only the amount of water, the temperature, and the chemical activity are reduced, but for one-half of the year the soil is locked up by frost from all access of decomposing agencies." The influence of these soils of disintegration upon the agriculture of the regions in which they occur, has often been noticed; and their bearing upon the history of the use and manufacture of commercial fertilizers in this country is no less clearly marked. It would seem to be plain, that disintegration such as this, when accompanied with or followed by denudation, would readily account for the accumulation, and, so to say, concentration in pockets,' or other places of rest, of any heavy or refractory minerals which were originally contained, dispersed, in the native rock; and that among the multitude of individuals thus thrown together there would be much greater likelihood of finding superior specimens than can be obtained by searching the comparatively meagre deposits that are formed at the north.

The statement of Nordenskiöld, above referred to, is here given in condensed form.

"Precious stones occur in Ceylon mainly in sand-beds, especially at places where streams of water have flowed which have rolled, crumbled down, and washed away a large part of the softer constituents of the sand, so that a gravel has been left which contains more of the harder precious-stone layer than the originally sandy strata or the rock from which they originated. Where this natural washing ends, the gem collector begins. He searches for a suitable valley, digs down a greater or less depth from the surface to the layer of clay mixed with coarse sand resting on the rock, which experience has taught him to contain gems.... The yield is very variable, sometimes abundant, sometimes very small. . . . Sapphires are found much more commonly than rubies. . . . The precious stones occur in nearly every river valley which runs from the mountain-heights in the interior of the island down to the lowland. . . . But some one perhaps will ask, Where is the mother-rock of all these treasures in the soil of Cey.

lon? The question is easily answered. All these minerals have once been embedded in the granitic gneiss which is the principal rock of the region" (and which weathers readily). . . ." In weath ering, the difficultly decomposable precious stones have not been attacked, or attacked only to a limited extent: they have there. fore retained their original form and hardness. When in the course of thousands of years, streams of water have flowed over the weathered rock, the softer constituents have been for the most part changed into a fine mud, and as such washed away, while the hard gems have only been inconsiderably rounded and little diminished in size. The current of water, therefore, has not been able to wash them far away from the place where they were ori ginally embedded in the rock; and we now find them collected in the gravel-bed, resting for the most part on the fundamental rock which the stream has left behind, and which afterwards, when the water has changed its course, has been again covered by new layers of mud, clay, and sand. . . . Of all the kinds of stones which are used for ornaments, there are both noble and cominon varieties, without there being any perceptible difference in their chemical composition. The most skilful chemist would have difficulty in finding, in their chemical composition, the least difference between corundum and sapphire or ruby; between common beryl and emerald; between the precious and common topaz; between the hyacinth and the common zircon; between precious and common spinel: and every mineralogist knows that there are innumerable intermediate stages between these minerals which are so dissimilar, though absolutely identical in composition. This gave the old naturalists occasion to speak of ripe and unripe precious stones. They said that in order to ripen precious stones the heat of the south was required. This transference of well-known circumstances from the vegetable to the mineral kingdom is certainly without justification. It points, however, to a remarkable and hitherto unexplained circumstance; namely, that the occurrence of precious stones is, with few exceptions, confined to southern regions... Another remarkable fact in connection with precious stones is, that most of those that come into the market are not found in the solid rock, but as loose grains in sand-beds. True jewel-mines are few, unproductive, and easily exhausted. From this, one would be inclined to suppose that precious stones actually undergo an ennobling process in the warm soil of the south."

To the writer of this note, it seems more reasonable to suppose that the greater abundance of noble gems in southern climates should be attributed to the more active and thorough-going disintegration which occurs in those regions, and to the consequent-comparatively speaking-enormous accumulation and concentration of the precious minerals, as above suggested. Other things might be far from being equal, and yet the chance of finding a stone of price be greater in a heap of ten thousand rough jewels than in a collection which contains but a few score. Bussey Institution.

F. H. STORER.

The November aurora in California. Auroras are exceedingly rare phenomena in southern California; yet we had the pleasure of witnessing one Nov. 17, at which time a great electric storm raged over North America and Europe. The photographic traces during the time from Nov. 10 to Nov. 20 are very interesting; as they have preserved a perfect record of the twitchings and jerkings, large and small, fast and slow, to which the magnets were subjected during this time.

A slight shock of earthquake was reported here on Jan. 23, about 5.20 P.M. I was on the street, and did not feel it; and so far as I can detect no harm was done at the observatory. MARCUS BAKER.

Los Angeles, Cal., Jan. 26.

TRYON'S CONCHOLOGY.

Structural and systematic conchology: an introduction to the study of the Mollusca; by GEORGE W. TRYON, JR. Vol. I. Philadelphia, the author. 1882. 8312 p., cuts, 22 pl. 8°.

WE have received the first volume of Mr. Tryon's new work (to be completed in three volumes), intended as an introduction to the study of the mollusks. This portion consists

As

of some general considerations, a description of the anatomy, habits, and economy, distribution in space and time, notes on nomenclature, classification and collection, of mollusks. sistance in paleontological matters has been rendered by Prof. Angelo Heilprin. The work is well printed and bound; but the plates, though not so bad as in the Manual' of the same author, contain mostly inferior renderings from old and familiar figures, produced by processes which cannot be made to yield really good results. The map is very badly drawn, and besides this, through overlaying," resulting from folding and inferior or excessive ink, has become nearly illegible. Mr. Tryon frankly disclaims authorship for his compilation, which is derived almost wholly from Woodward's well-known Manual,' and the earlier parts of Dr. Paul Fischer's Manuel de conchyliologie,' now in process of publication. Since both these works are accessible at a total price less than that of the first volume of Mr. Tryon's book, it is not clear why the latter should exist. Perhaps the future volumes will explain.

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Groups

Meanwhile we do not feel that any very warm welcome should be extended to a work of compilation so destitute of perspective as this. Though not what the author would have made it had Lovèn's work on the dentition of mollusks appeared ten years earlier, Woodward's book is nevertheless a thoroughly coherent manual, in which the parts retain proper proportions to each other and to the whole. There are many statements in it which are now obsolete, or supplemented by more precise, fuller, or more accurate information. not recognized by Woodward have attained their majority, and no longer train timidly in the leading-strings of a few bold specialists. The study of embryology, histology, and general anatomy, has entirely changed the situation so far as the point of view is concerned; but the great merits of Woodward, as originally published, are as conspicuous as ever. The work of Dr. Fischer is directly on Woodward's lines, and embodies of course much of his information; but it is not a mere revision, an ill-considered conglomeration like that of Tate, nor such a compilation as the present one of Tryon's. Silk and leather are good in their places; but man does not patch one with the other, or, doing so, repents of it. Mr. Tryon's first volume appears to us to resemble a mosaic of granite, chalk, precious stones, and mud, which is not delightful to the eye, neither will it wear. The work of the last twenty years in general, except so far as embodied in the ex