512 NATURE [JuLy 18, 1912 
daily frequencies for the four trimestres were:—N. | RECENT WORK IN MINERALOGY AND 
hemisphere, 0°3, 0°6, 0'4, and o'r; S. hemisphere, 13, PETROGRAPHY. 
r2, 14, and 11. Thus for the year the frequencies C. BRANNER, in studying the “Minerals 
were 04 (N.) and 12 (S.), as compared with 12 and 
1'4 respectively in 1910. The decrease throughout the 
year was fairly regular in the N. hemisphere, but in 
the southern there were very marked recrudescences 
in June, July, and August, and in October and 
November. On forty-five (24 per cent.) of the days 
of observation no prominences were to be seen. Taking 
the distribution of the prominences in 10° zones, there 
were two maxima, 20° to 29° and 40° to 49°, in the 
northern, and one maximum, 40° to 49°, in the 
southern hemisphere. 
THe Minor Pranet i911 MT.—It appears now 
that the period of the minor planet ro1r MT. is 
probably about five years, and that its aphelion lies 
beyond Jupiter’s orbit. The recovery of this small 
body, after its temporary loss soon after Dr. Palisa 
discovered it, is a wonderful astronomical achieve- 
ment, which Dr. Crommelin has likened to the re- 
covery of Ceres by Gauss. As a writer in The 
Observatory points out, Dr. Leuschner’s computers 
had, in the present case, only about one-sixth the 
length of arc, i.e. about half a degree, that Gauss 
had to work on in the case of Ceres. The new minor 
planet, according to Dr. Crommelin, is probably not 
more than four or five miles in diameter, but it can 
probably be kept sight of in future, and may prove 
useful in providing data for a determination of the 
earth’s mass from the periodic perturbations produced 
in its orbit by the comparatively massive earth. 
Tue VARIATION OF LatiruDE.—Prof. Albrecht’s sum- 
mary of the provisional results secured by the Inter- 
national Latitude Service in 19110 appears in 
No. 4588 of the Astronomische Nachrichten, accom- 
panied by the familiar spiral curve showing the pole’s 
wanderings since 1906. It would appear that the 
maximum departure from the mean position occurred 
in 1911, and the curve has now commenced to coil up 
again towards its centre; the uncoiling occupied the 
years 1906-11. The values along the x, y, and z 
coordinates for 1912'0, extrapolated, are +0'216", 
—o'076", and +0'079" respectively. 
Reports OF OBsERVATORIES.—In his report of the 
work done at the Oxford University Observatory 
during the year ending April 30, Prof. Turner states 
that the new method of obtaining differential places 
of the reference stars, for the astrographic catalogue, 
by photography is being given an extended trial; the 
results first obtained were so promising that one 
complete zone, +29°, is being observed. Already two- 
thirds of this zone has been covered, and some 16,450 
star images, on seven of the nine plates exposed, have 
been measured. The Oxford Observatory is also 
assisting the Watican Observatory in reducing the 
measures for the Vatican zones of the Astrographic 
Catalogue. : 
Among the many important items mentioned by Mr. 
Hough in his report of the work done at the Cape 
Observatory during 1911, we may note only one or 
two. The reductions of the transit-observations show 
that the azimuth-marks are remarkably stable, but 
there is a collimation discrepancy for which, so far, 
no adequate cause has been found. A new Hartmann 
spectro-comparator has been presented by Sir David 
Gill, and of the 1219 stellar spectra taken for radial- | 
velocity and solar parallax work, 875 have now been 
completely measured and reduced. For the coordina- 
tion of the stellar magnitudes in the Cape Astrographic 
zone forty ‘‘magnitude”’ plates, 160 exposures, were 
taken with the astrographic telescope, and with the 
photoheliograph 603 negatives of the sun were taken | 
on 293 days. 
NO. 2229, vo. 89] 
| member of this series of solutions. 
+ associated with Diamonds and Carbonados in) 
the State of Bahia, Brazil” (Amer. Journ. Sci., 
ser. 4, vol. xxxi., IgII, p. 480), comes to the con- 
clusion that the diamonds originated by metamorphic 
action in the quartzites in which they are occasion- 
ally found, together with other minerals characteristic 
of metamorphic rocks. The description given of 
these ‘Lavras quartzites,’ which may be of 
Carboniferous age, and the admitted proximity of 
gneissic and more highly metamorphosed rocks in the 
country round them (p. 489), make the reader will- 
ing to suspend judgment. 
E. T. Allen, J. L. Crenshaw, John Johnston, and 
E. S. Larsen issue a chemical and crystallographic 
study of the ‘‘ Mineral Sulphides of Iron”’ (ibid., vol. 
XXxXili., 1912, p. 169). Both marcasite and pyrite are 
shown to arise by the action of hydrogen sulphide 
upon salts of iron. Marcasite has been artificially 
formed from ferric sulphate in a closed vessel, which 
prevents the oxidation or escape of the hydrogen 
sulphide. The ferrous sulphate and sulphur produced 
are further acted on (p. 173) under these conditions 
by the hydrogen sulphide, yielding iron disulphide 
and sulphuric acid. Pyrite, instead of marcasite, 
arises where the solution remains neutral or but 
slightly acid (p. 181). Pyrite can also be made by 
the attack of a saturated solution of hydrogen 
sulphide in water on ferric hydroxide in a sealed tube, 
kept at 140° C. for seven days. These conditions 
may clearly be realised in nature. It is remarked 
(p. 191) that ferrous, and not ferric, sulphide has been 
observed to result from bacterial action in natural 
waters, such as those of the Black Sea, but an excess 
of hydrogen sulphide and an influx of air, bringing 
oxygen, would convert this into iron pyrites. Marca- 
site cannot exist at temperatures above 450° C., 
which probably accounts for the occurrence of pyrite 
in all deep veins. Pyrrhotine is carefully and experi- 
mentally considered, and is held to represent a solid 
solution, which accounts for the presence of sulphur 
in varying proportions (p. 194). ‘Troilite is an end 
Pyrrhotine is 
probably dimorphous, with a rhombic form arising 
at high temperatures and a hexagonal one at low 
temperatures. 
R. E. Liesegang (‘‘Die Entwicklungsgeschichte 
der Achate,” Aus der Natur, 1911, p. 561) shows how 
the colour-bands in agate can be imitated in a jelly 
of gelatine containing potassium bichromate. Silver 
nitrate is introduced in the centre, and the reaction 
spreads outwards, producing layers of silver chromate 
alternating with clear ones. The silver chromate 
first forms a supersaturated solution, but, as it 
spreads, the concentration causes precipitation. 
Diffusing through this layer, further silver nitrate 
repeats the process. It is urged that in nature a 
cavity may be filled by a silica jelly, and that iron salts 
may similarly spread through it, producing colour- 
bands. 
W. Hill usefully reviews British varieties of ‘* Flint 
and Chert,”’ of which he has such wide knowledge, in 
his address to the Geologists’ Association (Proc., 
vol. xxii., I9g1I, p. 61). 
Striiverite, which has attracted some attention, was 
first described from a granite dyke in South Dakota 
by L. Hess and R. C. Wells in 1911 (Amer. Journ. 
Sci., ser. 4, vol. xxxi., p. 432). Its composition is 
given approximately as Fe(Ta,Cb),O,.6TiO,,. 
C. Matveeff has examined specimens of cone-in- 
cone in anhydrite and calcite from the Ural district 
(Travaux de la Soc. imp. des Naturalistes de St. 
