5S2 



NA TURE 



[OCTOBEK 11,1 894 



of enlarging the displacement of the mercury column in the 

 manometer or barometer by means of a capillary filled with 

 oil, or containing an air-bubble, the new method is based 

 upon the principle of readjusting the level to a fixed mark by 

 the addition or subtraction of mercury, the quantity added or 

 subtracted being weighed or measured with a burette. If the 

 sectional area of the burette \i one-hundredth of that of the 

 manometer tube, a displacement in the former of i mm. will 

 indicate a difference of pressure of o'oi mm. To make the 

 method sensitive t is best to use water as the manometer liquid, 

 and to add or subtract mercury, which is more easily measured. 

 The chief ilesideratum is a simple method of adding or sub- 

 tracting, which is best done by attaching a sucking-tube to the 

 top of the burette. A pointer is fixed inside the manometer 

 tube opposite the centre of the meniscus. By observing the 

 reflection of the pointer in the surface, and the depressions or 

 elevations produced by the pointer, the observer is able to fix 

 upon the mark to within O'ooi mm. If mercury is used, an 

 electric contact is desirable. For barometer readings, pointers 

 can be mounted in both branches of the tube, and measure- 

 ments taken for both. Signor Guglielmo has also constructed 

 an absolute electrometer based upon this principle, in which 

 the level of mercury in a flat dish communicating with another 

 is disturbed by a charged disc, and readjusted by adding or 

 subtracting mercury. 



We have received from Dr. Luigi Palazzo, of the Meteorologi- 

 cal Office at Rome, an account of a small portable unifilar mag- 

 netometer which he has designed, and which is being employed 

 in the study of local magnetic disturbances in Italy. Signor 

 Palazzo does not claim any si)ecial novelty in the general de- 

 sign, which in many respects resembles the Kew form of port- 

 able unifilar. The instrument is designed for observing the 

 declination and horizontal force at strings of stations at one of 

 which the elements have been determined by means of one of 

 the more accurate and cumbersome forms of instrument. For 

 the purpose in view it was of importance to have an ins;ru- 

 ment which should combine extreme lightness with portability, 

 so that the different sets of observations along a line of 

 stations might be quickly taken, and thus, to a certain ex- 

 tent, the effects of disturbances minimised, since there does not 

 seem to be a self-recording magnetograph in the district 

 under investigation, from the photographic records of which 

 the disturbances could be eliminated. The azimuth circle 

 has a diameter of 8 cm. and carries the graduations on the rim, a 

 method of graduating the circle which, unless the tripod is very 

 high, and therefore un>lable, renders the reading of the verniers 

 a matter of difficulty. The magnet employed is a hollow 

 cylinder, as in the Kew instrument, carrying a photographic 

 scale at one end and a lens at the other. The mirror which is 

 used for illuminating the scale, as well as for reflecting the r.iys 

 of the sun when determining the geographical meridian, is com- 

 posed of a piece of parallel-sided plane unsilvcred glass mounted 

 on trunnions which are carried in V's of the ordinary form. The 

 whole insliumcnt packs into a box 28 x 12 x 18 cm. and only 

 weighs four kilograms. The author does not say with what 

 accuracy the horizontal component can be measured, but from 

 some figures given it would appear that the declination can be 

 determined to within about three minutes of arc ; which, con- 

 sidering ihc small size of the instrument, is remarkably good. 

 In order to facilitate the measurement of the bearing of land- 

 marks, ihc telescope is supportcrl on horizontal trunnions, so 

 that it can lie tilted in a vertical plane about 10 on either side 

 of the horizontal. 



Thr " ProctcdingJ of the Royal Physical Society of Edin- 

 burgh," Session l8<J3-94, is now ready, and may be purchased 

 at the Society's rooms, George-street, Edinburgh. 

 NO. 130?. VOL. 50] 



Prof. J. Shield Nicholson's lecture on " Historical Pro- 

 gress and Ideal Socialism," delivered at the Oxford meeting of 

 the British Association, has been published in handy volume 

 form by Messrs. A. and C. Black. 



We learn from the journal of Botany that the monograph 

 of the Mycetozoa, on which Mr. .\rthur Lister has been 

 engaged for some years, founded on the collection in the 

 herbarium of the British Museum, will shortly be published. 



Under the title " Xomenclator Coleopterologicus," H. 

 Bechhold, of Frankfort-on-Maine, has published, for Herr S. 

 Schlenkling, an etymological index, together with a list of species 

 and their varieties, of the beetles of German districts. The 

 book should be extremely useful to students of Coleoptera. 



Mr. Bernard Quaritch, Piccadilly, h.is issued a list of 

 choice and valuable books he has for sale, including the library 

 of the late Warren De la Rue. Many important works on 

 physics, chemistry, astronomy, electricity, mathematics, photo- 

 graphy, and microscopy are contained in the catalogue. 



We have received from the Skandinavisk Antiquariat, 

 Copenhagen, a catalogue of books, ancient and modern, of 

 Iceland and Scandinavia, which they have for sale. The cata. 

 logue, which will be sent free to all applicants, contains parti- 

 culars of books relating to bibliography, periodical literature, the 

 languages of the north, runology, mythology, archeology, 

 topography, &C. 



Chill October has come, and with it a new number of " The 

 Country Month by Month," in which Mrs. Owen and Prof. 

 Boulger describe the characteristics of the plant-world and 

 bird life during tlie month. The entomologiil's main occupa- 

 tion in October is digging up subterranean pup.-e, so the authors 

 give a brief account of insect metamorphosis. The chapter on 

 bird-life deals with the autumnal migration of our birds in a very 

 interesting manner. 



The Zoological Society of Germany has conferred a great 

 boon upon students of n.itural history by editing a reprint of 

 the tenth edition of Linn.-eus' " Systema Natura;." The first 

 volume, dealing with the animal kingdom, has lately been pub- 

 lished by Wilhelm Engelmann, Leipzig. It is well printed, 

 and will be very acceptable to those who ate not the fortunate 

 p issessors of a copy of the original ten ih and standard edition 

 of Linnaus' work. 



The sixteenth edition of their "Catalogue of Minerals and 

 Mineralogical Subjects " has been issued by Messrs. G. L. 

 English and Co., New York. The illustrations are all new, 

 and a complete revision of all Messrs. English's systematic col- 

 lections has been made. The species are classified according 

 to Dana's new "System of Mineralogy " (1892). The index 

 to the catalogue is jiarticularly valuable, for it enumerates all 

 species, and refers to the proper species all important synonyms 

 and varieties. 



A REMARK/MILE new Substance, obtained by the action of 

 ordinary alcohol upon peroxide of sodium, is described by 

 Prof. Tafel in the current licrichte. When alcohol is poured 

 upon sodium peroxide, about h.ill of the latter disappears to 

 form a strongly alkaline solution which contains practically no 

 active oxygen, while the remaining half undergoes a complete 

 c'lange. The pale yello*' colour of the commercial peroxide 

 becomes changed to pure white, and the substance assumes the 

 nature of a fine granular powder, loLilly different from peroxide 

 of sodium. This substance is soluble in water, but with much 

 less rise of temperature than the peroxide. While the hitter 

 compound is stable up to a high temperature, evolving no 

 oxygen when pure below redhcal, the new substance evolves 

 large quantities of oxygen upon gently warming, and if rapidly 



