Dec. 23, 1875] 



NATURE 



159 



natural beings analogous to the •vil spirits, devils, ghosts, a.nd 

 goblins of European superstition. According to Hindu doctrine 

 there are ten classes of such beings, the first seven of which are 

 demons created aboriginally with the world or by acts of the 

 higher gods on whom they wait as attendants or servants re- 

 ceiving some share of their worship, and avenging any omission 

 or neglect of ceremonies due. Though not invariably, they are 

 for the most part evilly-disposed towards human kind. But the 

 last three classes of whom the paper more particularly treated, 

 are exclusively of human origin, being malignant discontented 

 individuals, wandering in an intermediate state between a heaven 

 and a hell, intent upon mischief and annoyance to mortals, 

 chiefly by means of possession and wicked inspiration, every 

 aspect of which ancient ideas as well as of the old doctrine of 

 transmigration they exemplify and illustrate. They are known 

 by the name of Bhuta. The author went on to show how most 

 of the evils and misfortunes of life were attributable to the Bhuta 

 influence ; death from violence, evil possession, diseases in 

 families and in cattle, stone throwing, &c. He then described the 

 priestly use of those supposed powers, the cure of diseases, the 

 conduct of festivals, and dances. It was also pointed out how 

 close was the similarity between the occurrences imder Bhiita 

 influence and the prevalence of a belief among European nations 

 in witchcraft, demoniacal possessions, "levitations," ghosts, in- 

 visible powers, dancing manias, and the like. The Bhuta 

 empl9S and ceremonies were also described and compared with 

 those of the Todas and other hill tribes. The paper contained 

 accounts of several well authenticated trials consequent on Bhuta 

 interference and punishment. A series of Bhiita (Turanian) gods 

 was exhibited by the author as illustrative of the wide difference 

 between Turanian and Aryan art.— Mr. Groom Napier read a 

 paper on the localities whence the tin and gold of the ancients 

 were derived ; and a paper by Mr. Bertram F. Hartshorne on 

 the Weddas of Ceylon, was also read. 



Royal Microscopical Society, Nov. 24. — The president, 

 Mr. H. C. Sorby, F.R.S., described and exhibited his new con- 

 trivance for measuring the position of the absorption bands in 

 spectra. The new apparatus and its principle of action may 

 thus be described : — When polarised light passes along the line 

 of the principal axis of quartz, it does not suffer double refraction 

 and depolarisation, but circular polarisation. The result is that 

 when the quartz is l^ inch thick, and placed between two Nicol's 

 prisms, the spectrum of the light transmitted through it exhibits 

 seven well defined black bands, which gradually move up or 

 down the field of the spectrum on rotating one of the Nicols, 

 returning to the same place at each half-revolution. In order to 

 make use of this property in measuring the wave-lengths of dif- 

 ferent parts of any spectrum, the lower Nicol is permanently 

 fixed in a mounting connected with an ivory circle, each half of 

 which is divided into ten large divisions, and these again into 

 five smaller, so that it is easy to read off to the 1^ part of a 

 half revolution. This of course corresponds to ^-^ of the in- 

 tervals between any two of the seven bands. Placing the circle 

 at the zero point, the other Nicol's prism can be rotated until 

 the bright line of sodium is all but invisible in the centre of total 

 interference of the second band, counting from the red end. The 

 position of all the other bands is then also definite and constant. 

 By using a diffraction spectroscope the: wave-lengths of all the 

 bands and of each ^V interval can be calculated and arranged in 

 a table and the smaller intervals can be filled up by interpola- 

 tion. There is then no difficulty in determining the wave-length 

 of the centre of any well-marked absorption band seen in the 

 spectrum of any substance which is compared side by side with 

 that of the quartz ; for which purpose the binocular form of 

 apparatus described by Mr. Sorby is the most convenient. The 

 number of the band counting from the red end is easily seen, and 

 the fractional interval is easily measured by rotating the ivory 

 circle until the centres of the bands are made to exactly coincide. 

 In the case of well-marked absorption-bands consecutive readings 

 differ by only what is equivalent to one-millionth of a millimetre 

 of wave-length, and the means of several observations differ con- 

 siderably less than that. By proper attention to the illumination 

 of both spectra there appears to be no serious difficulty in mea- 

 suring the position of well-defined absorption-bands to within 

 one-millionth of a millimetre of wave-length, which is quite as 

 near as appears to be necessary in the case of the spectra for 

 which the instrument is designed. 



Geologists' Association, Dec. 3. — Mr. Wm. Carruthers, 

 F.R.S., president, in the chair.— On quartz, chalcedony, agate, 

 flint, chert, jasper, and other forms of silica geologically consi. 



dered, by Prof. T. Rupert Jones, F.R.S. After noting a few 

 of the salient mineralogical features of quartz, pointing out the 

 difference in specific gravity between fused quartz (2 '2) and 

 ordinary quartz {2 '6), the author passed on to chalcedony, which 

 bears a similar relation to quartz that barley-sugar does to sugar- 

 candy. No definite crystallised structure can be observed ; but 

 a fibrous appearance may generally be noted, at right angles to 

 the planes of deposit, which latter often render the mass flaky. 

 In some specimens this fibrous structure gradually becomes 

 stronger, close-set, minute, crystalline prisms being visible in the 

 fracture, ,and these pass into regular quartz crystals. The sub- 

 crystalline structure of chalcedony is not yet thoroughly worked 

 out. On account of the unequal resistance of some chalcedonies 

 in agates to the .action of hydrofluoric acid, by which certain 

 layers are eaten away, cut agates have been prepared in slabs 

 which take printer's ink and give impressions of their concentric 

 structure, and of the channels of infiltration (See Transact. R. 

 Acad. Vienna, &c.). Speaking of the formation of the angles 

 in "fortification-agates," the author was inclined to accept the 

 hypothesis of the chalcedonic silica having replaced calcite or a 

 zeolite ; a portion of an agate, comprising fiat transverse layers of 

 chalcedony, with quartz and calcite, being exhibited in illustra- 

 tion. The porous nature of agates, and the facilities thus afforded 

 for the absorption of colouring matter, artificially introduced, 

 were alluded to as connected with the minute prismatic structure. 

 The properties of flint are somewhat different ; it is less trans- 

 lucent, more conchoidal in fracture, and never fibrous in struc- 

 ture. Aggregations of silica were stated to be present in every 

 limestone, either in the form of common flint or as homstone, or 

 some variety of chert, and were regarded by the author as being 

 due to the replacement of carbonate of lime by silica. But as 

 this, mineral rarely succeeds calcite (crystallised calcic carbonate) 

 as a pseudomorph, it is only the amorphous, or detrital, car- 

 bonate of lime of the organisms constituting the limestone that 

 becomes changed into, or replaced by, silica (as flint), and not 

 the crystallised material of Echmodermatal structures (whether 

 spmes, plates, stems, or ossicles), nor of Inoceramus, Ostrea, 

 Terebratula, &c. These latter, however, in some cases are 

 replaced by orbicular silex. When such unchanged organisms 

 are abundantly present in flint, or when they have left cavities 

 after removal by water, or when other partially altered organisms 

 abound in the flmt, it appears coarse-grained and is called 

 " chert." The fine calcareous detritus which filled the internal 

 canal of encrinital stems, the perforations of echinite tests, the 

 parasitical borings of oyster-shells and belemmites, the tubules of 

 sponges, the cavities of sea-urchins, shells, foraminifera, &c., has 

 been changed, atom by atom, into exquisite silicious casts of such 

 hollows and interiors, and are exposed to light by the natural or 

 artificial removal of the calcareous enclosure. In some beds of 

 chalk the pseudomorphosis of the limestone has taken place 

 near and around Sponges ; elsewhere, without Sponges, large 

 masses of Polyzoan Chalk have been siHcified (France, Maes- 

 tricht, &c. ) ; also Orbitoidal and Nummulitic limestones (West 

 Indies, Alps, &c.) Freshwater limestones (Paris, Asia Minor, &c.) 

 Encrirital limestone (Carboniferous, Britain, and Tasmania). 

 The white surface of a fresh chalkflint, of whatever shape it may 

 be, shows by its rough subreticular surface, dotted with un- 

 changed microzoa and fragments of shells, the extent of the 

 creeping, pseudomorphic change between the nodule and the 

 matrix, and the replacement by silica has been through just so 

 much chalk or other limestone as the nodule or tabular mass 

 represents in size. Even some vertical flint- veins in chalk the 

 author believes to consist of the two altered walls of a fissure, 

 which has been traversed by water with silex in solution ; for 

 chalk fossils remain sometimes in situ in such vein flint. The 

 author believed that in the south of England, at least, it is rare 

 for sponge-structure to be itself converted into flint. This sub- 

 stance represents the calcareous mud filling the cavities of the 

 sponge, the tissue having generally been lost, or remaining 

 only as a ferruginous stain. Hollows in flints due to the 

 removal of involved sponge-tissue have been lined, by infil- 

 tration, with either quartz-crystals or mammillary chalcedony. 

 The specks, blotches, lines, and some other markings apparent 

 on weathered flint, the author thinks, in many cases, arise from 

 differences in the texture of the flint, due to the various organic 

 substances inhabiting or buried in the calcareous mud now repre- 

 sented by pseudomorphic silex. Among such organisms, he 

 suggests that the recent thread-like Foraminifera {Boklli>ia, &c. ) 

 of the Atlantic ooze may have had their analogies in the Creta- 

 ceous mud, giving rise to some straight and cross-fined markings 

 on the weathered surfaces of broken flint, and somewhat similar, 



