434 



NA TURE 



[April 2, 1874. 



rature of the two wires could be perceived, thereby proving that 

 not even a small proportion of the current was repulsed from 

 the repelled wire, or drawn into the attracted one, as would 

 have occurred had the attraction and repulsion taken place, even 

 to a moderate degree, between the currents themselves ; and I 

 therefore conclude that //;<? al/ractions and repulsions of electric 

 conductors are not exerted between the currents themselves, hut 

 betKieen the substances conveying them. 



Some important consequences appear to flow from this conclu- 

 sion, especially when it is considered in connection with 

 Ampere's theory of magnetism, and with the molecular changes 

 produced in bodies generally by electric currents and magnetism. 



As every molecular disturbance produces an electric alteration 

 in bodies so, conversely, the discoveries of numerous investigators 

 have shown that every electric current passing near or through a 

 substance produces a molecular change, which is rendered 

 manifest in all vessels, liquid conductors, and even in the 

 voltaic arc by the development of sounds, especially if the sub- 

 stances are under the influence of two currents at right angles to 

 each other. In iron it is conspicuously shown also by electro- 

 torsion, a phenomenon I have found and recently made known in 

 a paper read before the Royal Society. 



Numerous facts also support the conclusion that the molecular 

 changes referred to last as long as the current. De la Rive 

 has shown that a rod of iron, either transmitting or encircled by 

 an electric current, emits, as long as the current lasts, a different 

 sound when struck ; and we know it also exhibits magnetism. 

 The peculiar optical properties of glass and other bodies with 

 regard to polarised light discovered by Faraday also continue as 

 long as the current. A rod of iron also remains twisted as long 

 as it transmits and is encircled by electric currents ; and in steel 

 and iron the molecular change (like magnetism) partly remains 

 after the currents cease, and enables the bar to remain twisted. 



That the peculiar molecular structure produced in bodies 

 generally by the action of electric currents also possesses a defi- 

 nite direction with regard to that of the current, is shown by the 

 rigidly definite direction of action of magnetised glass and many 

 other transparent bodies upon polarised light ; also by the differ- 

 ence of conductivity for heat and for electricity in a plate of 

 iron parallel or transverse to electric currents ; by the sti'atified 

 character of electric discharges in rarefied gases, and the action 

 of electric currents upon it ; and especially by the phenomenon 

 of electro-torsion. In the latter example an upward current pro- 

 duces a reverse direction of twist to a downward one, and a 

 right-handed current developes an opposite torsion to a left- 

 handed one ; and the two latter are each internally different from 

 the former. As each of these four torsions is an outward mani- 

 festation of the collective result of internal molecular disturbance, 

 and possesses different properties, these four cases prove the ex- 

 istence of four distinct molecular movements and four correspond- 

 ing directions of structure ; and the phenomena altogether are of 

 the most rigidly definite character. 



As an electric current imparts a definite direction of molecular 

 structure to bodies, and as the attractions and repulsions of elec- 

 tric wires are between the wires themselves and not between the 

 currents, repulsion instead of attraction must be due to difference 

 of direction of structure produced by difference of direction of 

 the currents. 



Although the Amperean theory has rendered immense service 

 to magnetic science, and agrees admirably with all the pheno- 

 mena of electro-magnetic attraction, repulsion, and motion, it is 

 in some respects defective ; it assumes that magnetism is due to 

 innumerable little electric currents continually circulating in one 

 uniform direction round the molecules of tlie iron ; but there is 

 no known instance of electric currents being maintained without 

 the consumption of power, and in magnets there is no source of 

 power ; electric currents also generate heat, but a magnet is not 

 a heated body. 



If, however, we substitute the view that the phenomena of at- 

 traction and repulsion of magnets are due, not to continuously 

 circulating electric currents, but (as in electric wires) to definite 

 directions of molecular structure, such as is shown by the pheno- 

 mena of electru-torsion to really exist in them, the theory be- 

 comes more perfect. It would also agree with the fact that iron 

 and steel have the power of retaining both magnetism and the 

 electro-torsional state after the currents or other causes producing 

 them have ceased. 



According to this view, a magnet, like a spring, is not a source 

 of power, but only an arrangement for storing it up, the power 

 being retained by some internal disposition of its particles acting 



like a " ratchet," and termed " coercive power." The fact that a 

 magnet becomes warm when its variations of magnetism are 

 great and rapidly repeated, does not contradict this view, because 

 we know it has then, like any other conductor of electricity, elec- 

 tric currents induced in it, and these develop heat by conduc. 

 tion-resistance. 



According also to this view any method which will produce 

 the requisite direction of structure in a body will impart to it the 

 capacity of being acted upon by a magnet ; and any substance, 

 fenuginous or not, which possesses that structure has that capa- 

 city ; and in accordance with this we find tint a crystal of cyanite 

 (a silicate of alumina) possesses the property, whilst freely sus- 

 pended, of pointing north and south by the directive influence ot 

 terrestrial magnetism, and one of stannite (o.xide of tin) points 

 east and west under the same conditions. 



Geological Society, March II.— John Evans, F.R.S., 

 president, in the chair. — The following communications were 

 read : — On the relationship existing between the Echinothurides 

 Wyville Thomson and the Pcrischocchinidic McCoy, by R. 

 Etheridge, jun. In this paper the author referred in the first place 

 to the peculiar characters of the genera Calveria and Phormosoma 

 Wyville Thomson, and especially to those in which they approach 

 the cretaceous genus Echinothuria S. P. Woodward, and which 

 led Prof. Wyville Thomson to include these three forms in his 

 group EchinothuridcE. He remarked that an overlapping of the 

 interambulacral plates, more or less like that occurring in these 

 three genera, is met with also in Archaocidaris McCoy, and 

 Lcpidechinus Hall, belonging to the group of palxozoic Echini 

 wliich McCoy proposed to call Perischoechinida;, and which 

 is characterised by the presence of more than three rows of plates 

 in the inter-ambulacral areas. As there is no overlapping of these 

 plates in the other genera referred to this group, it includes two 

 types of structure. The author then discussed the characters pre- 

 sented by the test in the genera of the Perischoechinidse (namely, 

 Archtcocidaris, Pahcchinus Perischodonius, Lcpidechinus, Eoci- 

 daris, Melonites, and Oligoporus), and pointed out that although 

 we have no conclusive evidence of the presence of membranous 

 interspaces along with the overlapping plates in Archicocidaris, 

 the fragmentary condition in which the remains of that form are 

 usually found would lead us to infer their existence. No known 

 palaeozoic genus exhibits the want of distinction between the 

 ambulacra and interamhulacra on the ventral half of the test 

 seen in the recent genus Phormosoma. In Melonites and Oligo- 

 porus the author described an increase in the number of rows ot 

 plates in the ambulacra, and he indicated that all the Peris- 

 choechinida; differ from the later Echini by the increased 

 number of perforations in the ocular and genital plates. — 

 On the discovery of Foraminifera, &c., in the boulder-clays of 

 Cheshire, b«/ William Shone, jun. In this paper the author 

 described the occurrence of Foraminifera, Entoii! > traca, and 

 some other small organic bodies in the boulder-cl.) .it Newton 

 by Chester and at Dawpool. They were found partly in the 

 interior of specimens of Turritella terebra, and partly free in the 

 boulder-clay. — On the occurrence of a Tremadoc area near the 

 Wrekin in South Shropshire, with description of a new fauna, 

 by Charles Callaway. The author stated that in an exposure of 

 light green, micaceous shales dipping south-east at 50° at 

 Shineton near Cressage, which are represented as of Caradoc 

 age in the Geological Survey Map, he found a series of trilobites 

 and other fossils wliich induced him to regard these Shineton 

 shales as belonging to the Lower Tremadoc series. He de- 

 scribed as new species : — Asciphus eos, Conoeoryphc salteri, C. 

 angulifrons, Platypeltis croftii Cotwphrys sahpicnsis, Lichapyge 

 cuspidata, Lingulella nicholsoni, Metoptoma sitbrinit, and Theca 

 Hneata. The author regarded these shales as the equivalents of 

 beds containing Dictyonema, found near Malvern and at Pedwar- 

 dine. 



Anthropological Institute, Mnrch24. — Prof. George Busk, 

 F. R.S, president, in the chair. — The President exhibited and 

 described an Ashanti skull. The specimen, with other bones of 

 the iiody, waslaken bySu geon-VIajorGore from an outlying camp 

 which had been deserted on the approach of the British troops. 

 It presented the characteristics rather ot a female than a male 

 skull, but Mr. Gore affirmed that he had never heard of the 

 Ashantis carrying about the bones of a woman. Women, in 

 fact, held such an inferior position, that it could scarcely be be- 

 lieved that the Ashantis would take trouble in the preservation 

 of their remains. If the skull exhibited belonged to a man, he 

 could not have been a military leader, but he might have had 



