April 5, 1894] 



NA 1 URE 



547 



to the stu'ly of chemical reactions, by J. Ver>chaffeh. The Pul- 

 frich lerr.iciome er used, when compared vvith a standard spec- 

 trometer, ijave a constant difference in the index of refraction 

 amouniiiig to -o 00069, this being probably due to the inser- 

 tion of a ptism of different material in the refractometer. With 

 this correction the refractometer readings could be taken as 

 absolutely trustworthy to the fourth decimal place. The author 

 shows that all disas^reements with the law governing the index 

 of refraction of mixture- indicate a chemical reaction (i) if the 

 observed index is lower than the calculated index ; or (2) if it 

 is higher hy such an amount that the difference cannot be attri- 

 buted to a change of volume. — On the parietal eye, the epi- 

 physis, the paraphysi<, and the choroid plexus of the third 

 ventricle, by P. Francotti. This paper contains a detailed 

 description, illustrated by excellent microphotographs, of these 

 rudimentary organs as they appear in the slow-worm and the 

 human embryo. 



IVitdemann s Annalen der Physik und Chemie, No. 3. — On 

 elliptic polarisation of reflected light, by K. E. F. Schmidt. 

 This fir^t part of the work deals with the influence of foreign 

 surface layers. Contrary to the conclusions of Drude, 

 Rontgen, and Lord Kayleigh, the author shows that no obser- 

 vation jusiifies us in assuming that the elliptic polarisation of 

 light reflected from polished surfaces is produced by layers of 

 the polishing material. The polish attached to the mirror is 

 only capable of modifying the phenomenon. The constancy of 

 the ellipticiiy of light reflected from mirrors cleaned by means 

 of a gelatine film, which is pulled nff when hardened, implies 

 a constancy of the cause of this phenomenon, independent of 

 the polishing powder used. — Remarks upon Paschen's paper 

 on " The emission of heated gases," by E. Prinii--heim. The 

 author maintains that the so-called discontinuous heat spectra 

 observed by Paschen, cannot be fitly described as :-uch, since 

 the " band " due to COo extends over a region three times as 

 large, and that of steam over one twenty times as large, as the 

 whole visii)le S|iectrum. — On normal and anomalous changes 

 of phase during the reflection of light by metals, by W. 

 Wernicke. The change of phase pro luced by the reflection of 

 light from a silver film between two transparent media, the 

 anterior one of which has the higher index of refraction, is an 

 acceleration which increases continuously from zero to ^ or | of a 

 wave-length as the thickness of the silver grows from zero to 

 opacity. This is the normal change of phase. An anomalous 

 retardation takes place when there are traces of another 

 substance between the silver and the front medium. It may 

 amount to something between \ and | of a wave-length. — On 

 the proportionality between lowering of freezing point and 

 osmotic pressure, hy S vante Arrhenius. — On a more exact method 

 for the determination of the lowering of freezing points, by E. 

 H. Loomis. The apparatus used was an impr ived form of 

 Beckmann's freezing tube. To avoid the fluctuations of 

 temperature associated with the melting or solidifying of ice in 

 water, sometimes amounung to 01° C, the tube was lengthened 

 so as to remove the substance from the warmer air, and a 

 freezing mixture was in each case employed, which gave a tem- 

 perature only about 0'3° lower than the actual freezing point of 

 the substance experimented upon. 



In the numbers of the fournal of Bjtany for Mirch and 

 April, the articles are almost entirely descriptive. Mr. E. G. 

 Baker has an interesting paper on the section Rkynchypetalmn 

 of Lobelia, in which two new species from Africa are described 

 and figured. 



SOCIETIES AND ACADEMIES. 



London. 



Royal Meteorological Society, March 21. — Mr. R. 

 Inwards, President, in the chair. — Mr. W. H. Dines read a 

 paper on the relation between the mean quarterly temperature 

 and the death-rate. The Registrar-General's Quarterly Re- 

 turns for the whole of EngLin.l since 1862 were taken by the 

 auth'T, and the number of deaths in each quarter expressed as 

 a departure per thousand from that particular quarter'- average ; 

 the value so obtained being placed side by side with the corre- 

 sponding departure of the temperature at Greenwich from its 

 mean value. The rule seems to be that a cold winter is un- 

 healthy, and a mild winter healthy; and that a hot summer is 

 always unhealthy, and a cold summer healthy. Mr. Dines also 



NO. 1275 VOL. 49] 



read a paper on the duration and lateral extent of gusts of wind 

 and the measurement of their intensity. From observations 

 and experiments which he has made with his new anemometer, 

 Mr. Dines is inclined to think that a gust seldom maintains its 

 full force for more than one or two seconds ; and also that the 

 extreme velocity mostly occurs in lines which are roughly 

 parallel to the direction of the wind. — Mr. R. H. Scott, 

 F.R. S., exhibited a diagram showing some remarkable sudden 

 changes of the barometer in the Hebrides on February 23, 

 1894. At 8 a.m. the reading at Stornoway was 29'39 inches, 

 being a fall of 0"7 inch since the previous day, and at 6 p.m. 

 the reading was 28"58 inches. From the trace of the self- 

 recording aneroid it appears that the minimum, 28 '50 inches, 

 occurred about 5.30 p.m., and that the fall during the half-hour 

 preceding the minimum was nearly 0'2 inch, the rise after the 

 minimum being nearly as rapid. — The other paper read was 

 on the calculation of photographic cloud measurements, by Dr. 

 K. G. Olsson. 



Geological Society, March 21. — -Dr. Henry Woodward, 

 F. R.S., President, in the chair. — The following communica- 

 tions were read : — On the origin of certain novaculites and 

 quartzites, by Frank Rutley. The novaculites of Arkansas 

 have already been admirably described by Mr. Griswold 

 in vol. iii. of the Arkansas Survey Report for 1890. One 

 of the characteristic microscopic features in Ouachita stone 

 is there stated to consist in the presence of numerous 

 cavities, often of sharply-defined rhombohedral form, which 

 Mr. Griswold con-aiders to have been originally occupied 

 by crystals of calcite or dol >mite. The author, while 

 admitting that the cavities were no doubt once filled by the 

 latter mineral, differs from Mr. Griswold, and some of the 

 authorities he cites, concerning the origin of the rock. Crystal- 

 line dolomites, when dissolving, become disintegrated into 

 minute but well-formed rhombohedra. As the process of dis- 

 solution proceeds these crystals may become so eroded that the 

 rhombohedral form is no longer to be recognised. The author 

 pointed out that no inconsiderable proportion of the cavities in 

 Ouachita stone present irregular boundaries, such as the moulds 

 of partially eroded rhombohedra would show. He then offered 

 a fresh interpretation of these cavities, so far as the origin of 

 the rock was concerned : (i) He assumed that beds of crystal- 

 line magnesian limestone have been slowly dissolved by ordinary 

 atmospheric agency and the percolatiim of water charged with 

 carbonic acid or other solvent. (2) That, as the limestone was 

 being dissolved, it was at the same time being replaced by silica, 

 which enveloped minute isolated crystals and groups of crystals, 

 some perfect, others in various stages of erosion. (3) That the 

 silica assumed the condition of chalcedony, its specific gravity, 

 as stated by Mr. Griswold and as determined by the author, 

 being low in comparison with that of quartz. (4) The residuum 

 of the original dolomite or dolomitic limestone was removed, 

 leaving the perfect and imperfect rhombohedral cavities. A 

 calciferous, gold-bearing quartzite from the Zuluiand gold-fields 

 was described, and a similar origin ascribed to it, but in this 

 case the original rock appears to have been simply a limestone, 

 not a dolomite. The gold seemed to occur chiefly in the cal- 

 careous portions of the rock. The author also suggested a similar 

 origin for the saddle-reefs of the B^ndigo gold-field. In all of 

 these cases the train of reasoning is based upon the conclusions 

 arrived at in his previous paper, "On the dwindling and dis- 

 appearance of limestones." He indicated that the strati- 

 graphical relations of the Arkansas novaculites, as described in 

 Mr. Griswold's report, were such as to warrant the assumption 

 that limestones once occuneJ in the position now occupied by 

 beds of novaculite. Many collateral matters were dealt with in 

 the paper which cannot be given in abstract; among them was 

 an attempt to classily quartzites. Dr. G. J. Hinde and Prof. 

 Hull discussed some of the conclusions in the paper, and the 

 author briefly replied. — Note on the occurrence of perliiic cracks 

 in quartz, by W. W. Watts. The author of this communication 

 described some Sjiecimens of the porphyritic pitchstone of Sandy 

 Braes in Antrim, which are deposited in the Mu-eum of Science 

 and Art in Dublin, and in that of Practical Geology in Jermyn 

 Street. They exhibit admirable examples of perlitic structure 

 in the brown glassy matrix, and the presence of polygonal, cir- 

 cumferential, and radial cracks is noiiced. The p <rphyritic 

 cry.stals of quartz are traversed by curved fissures of retreat, not 

 so perfect as those found in the glass, but better than those 

 usually produced by the rapid c loling of Canada balsam. The 

 fissures in the quartz are frequently prolonged into the matrix, 



