NovemBeER 16, 1916] 
NATURE 
con 
out free silica. All the rocks are rich in titaniferous 
magnetite, and analyses indicate that their most. note- 
worthy feature is the unusual abundance of titania. 
The analyses cannot be closely matched except by those 
of basalts from Scoresby Sound, Iceland, the Farée 
Islands, and the west gf Scotland. This paper is the 
first of a series in which the authors hope to describe 
rocks from all the important localities within the 
province.—Miss N. Hosali exhibited models of crystals 
constructed by herself. 
Optical Society, November 9.—Mr. F. J. Cheshire, 
president, in the chair.—J. W. French: The grinding 
and polishing of optical surfaces. The polished sur- 
face of metals consists of a layer which covers over 
small scratches and pits in the underlying material. 
When the surface layer is removed by etching, the 
scratches and pits are exposed. When the polished 
surface of glass is etched, numerous fine scratches 
reappear, and it has been wrongly assumed that glass 
behaves like metals. For purposes of description, the 
original material is referred to as a glass and the modi- 
fied material constituting the surface layer as B glass. 
Clean scratches comparable with those on metal cannot 
be formed on the a glass. The material splinters in 
the characteristic conchoidal fashion. . Perfectly clean 
scratches can be formed in the f layer; they can be 
filled in by further polishing, and it is these scratches’ 
that reappear after etching. The cohesion of the sili- 
cates constituting the surface layer is too small to 
permit of the bridging over of pits, such as minute 
airbells, that are just exposed, and no evidence of any 
inclusion of foreign matter in the B layer scratches 
has been obtained. An optical glass surface is pro- 
duced as follows :—The action of the pitch polisher 
loosens or liquefies, as it were, the surface layer of 
molecules, which rearrange themselves uniformly under 
surface tension. The polishing medium subdivides, 
breaks up, and removes the surface layer, thus expos- 
ing the underlying material. This process then re- 
peats itself, and a perfect surface is obtained only by 
the removal .of material beyond the bottom of the 
hollows produced in the glass during the earlier 
abrasion process. 
Paris. 
Academy of Sciences, October 23.—M. Camille Jordan 
in the chair.—The President announced the death of 
M. E. F. Maupas, correspondant in the section of 
anatomy and zoology.—A. Lacroix: The volcanic 
glasses of the,Cantal massif.—G. Humbert ;: Some re- 
markable numerical functions.—C. de la Vallée Poussin; 
The zeros of ((s) of Riemann.—A. Verschafiel ; Advan- 
tages of circles both mobile and with multiple origin. 
—W. H. Young: Trigonometrical series and the means 
of Cesaro.—D., Pompeiu: Series with positive terms 
and the derived functions.—D, Menchoff : The unicity 
of the trigonometrical development.—J. Guillaume : 
Observations of. the sun made at the Observatory of 
Lyons during the third quarter of 1916. Details of 
observations made on seventy-nine days during the 
quarter.—C, Camichel: The determination of the velo- 
city of propagation a in high-pressure water mains.— 
C. Zenghelis and S, Horsch: The chemical action of 
sodium peroxide upon hydrogen sulphide. The main 
product of the reaction is sulphide; polysulphides, 
sulphate, and thiosulphate are formed in smaller quan- 
tities—Ph,  Flajolet: Perturbations of the magnetic 
declination at Lyons (Saint-Genis-Laval) during the 
second quarter of 1916.—L. Vegard and O. Krogness : The 
results of observations of the aurora borealis carried 
out at the Observatory of Haldde. The discussion of 
determinations of heights measured by photographs 
taken simultaneously from two points. The lower 
NO. 2455, VOL. 98] 
limit of height always exceeds 85. kilometres, the 
upper. limit from. 100 to 330 kilometres.—G, 
Bourguignon and J: Lucas: Classification of the muscles 
of the superior member in man following ‘their radi- 
cular systematisation, by the velocity index of excit- 
ability.—_M. Weinberg and P. Séguin: Contribution to 
the etiology of gaseous gangrene. A description of.a 
new bacillus (B. histolyticus) which, while incapable 
of itself producing a gaseous infection, appears to 
play an important part in the etiology of certain cases 
of gaseous gangrene. 
. October 30.—M, Camille Jordan in the chair.—G. 
Bigourdan ; Astronomical observations at Paris from 
1632 to the foundation of the Observatory. From 1632 
to 1637 work was done by Gassendi, Beaugrand, 
Boulliau, and Descartes. About this period there 
commenced scientific gatherings which later resulted 
in the formation of the Academy of Sciences. The 
solar eclipse of June 1, 1639, was observed by three 
different groups. The paper concludes with a tabular 
statement showing the more important observations 
made between 1653 and 1667.—H. Le Chatelier and F. 
Bogitch: The determination of the density of solid 
bodies. A discussion of the chief causes of error in 
density measurements of solids. The method sug- 
gested is based on the direct measurement in a narrow 
graduated tube of a liquid by the powdered solid. It 
is shown that either benzene, carbon tetrachloride, or 
petroleum spirit may serve as the displaced liquid, but 
that water is quite unsuitable—M. Hamy: A reduc- 
tion formula for prismatic spectra.—MM. Costantin 
and Bois: The varieties of vanilla——C. de la Vallée 
Poussin: The Riemann zeros of ¢(s).—W. Kilian: The 
exact age of the ‘‘Plaine des Rocailles,” “near the 
Roche-sur-Foron (Haute-Savoie), and  fluvioglacial 
stages of Genevois-Faucigny.—L. Bouchet : The varia- 
tions of thickness of a caoutchouc sheet under the 
influence of an electrostatic field. It is proved experi- 
mentally that under the action of an electrostatic field 
vulcanised india-rubber contracts in the direction of 
the lines of force.—J. Bougault: The semicarbazones 
of the a-ketonic acids. a-Di-iodo- and a-dibromo- 
phenylbutyric acids. a-lodo- and a-bromo-phenyl- 
crotonic acids.—L. Daniel ; Experimental cultures at the 
seashore. In the course of fifteen years plants of 
various kinds, transferred from Rennes to Erquy, 
near the sea, have acquired none of the characteristics 
of halophytic plants.—P. Lesage : Trials of the seeds of 
Lepidium sativum under varying conditions. The 
effects of germination in dilute potash solutions, in 
alcoholic solutions, in solutions of chlorides, nitrates 
and sulphates of potassium, sodium, and ammonium 
were studied. The effects of time of immersion, soak- 
ing in petrol or ether, of moist air, and of solutions 
of hydrogen peroxide are also given.—F, Vincens: A 
Verticilliaceze of doubtful affinities—M. Baudouin : 
Results of the examination of the mandible of a young 
infant of the polished Stone age.—W. T. Porter: Low 
arterial pressures and their treatment. Experiments 
on animals have proved that when the diastolic pres- 
sure is as low as 45 mm. to 50 mm.,, unless appro- 
priate treatment is applied the animal dies. Observa- 
tions on wounded at the front show that there is no 
essential difference between the effects of a low pressure 
in man and in animals, and the same mode of treat- 
ment can be applied with success in both cases. The 
means adopted are :—(1) Mechanical; (2) adrenaline ; 
(3) injection of isotonic serum.—Ch. Richet ; Remarks 
on the preceding paper.—J. Beauyerie: Researches on 
the influence of the osmotic pressure on bacteria. The 
case of the cholera vibrion.—L. C, Bailleul and P. 
Girard: The polarisation of the cicatricial tissue and 
the electrical treatment of deep cicatricial adherences. 
