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NA TURE 



[July 20, 189; 



tioned that only last September a circular was addressed by the 

 German Government to the commanders of cavalry, ordering the 

 injectionof" malleine " into the horses of those regiments where 

 cases of glanders were proved to have occurred. 



The fact that some micro-organisms may stimulate or depress 

 the vitality or virulence of others has been taken advantage of 

 by both Sanarelli and Chantemesse and Widal in their recent 

 researches on immunity and typhoid (evsr (Annates de I'lnslitut 

 Pasteur, 1892). The typhoid bacillus very rapidly loses its 

 pathogenic properties when cultivated for any length of time 

 outside the living body. Its virulence may, however, be 

 revived by introducing it into an animal along with sterilised 

 cultures of some special organisms. Sanarelli used sterilised 

 cultures of the B. coli communis, beginning with 10-12 cc, and 

 gradually diminishing the dose, until the typhoid bacillus, as 

 taken from the last animal, proved virulent without any addi- 

 tion. Sterilised cultures of the Proteus vulgaris may, according 

 to Sanarelli, be also used. Chantemesse and Widal obtained 

 the same results by employing sterilised cultures of the Strepto- 

 coccus pyogenes, it having been found by Vincent that in the 

 most serious cases of typhoid fever which he examined the 

 latter was present along with the typhoid bacillus. 



The true origin ot contrast colours is still a much-debated 

 question among physicists. The Young-Helmholtz hypothesis 

 of colour sensation assumes that the perception of a contrast 

 colour by which, for instance, a shadow cast by a candle in day- 

 light appears blue, is due to an error of judgment brought about 

 by falsely taking the candle as representing white light and 

 "dividing the difference of tint between the various portions 

 of the surface equally between them." Mr. Alfred M. Mayer, 

 in the American Journal of Science, attempts to show by a 

 series of experiments that the perception of contrast-colour is 

 due to purely physiological, and not to psychical causes. Some 

 careful chronograph experiments showed that the perception of 

 a contrast colour did certainly not require more than one-fif- 

 teenth of a second. A spark from a Holtz machine, lasting a 

 millionth of a second and 8cm. long, made a grey ring on an 

 emerald green ground appear a bright pink. The spark was 

 also passed between brass knobs placed in front of a piece of 

 silvered mirror half covered with a piece of green glass. The 

 path of the spark presented a remarkable appearance. The 

 portion reflected from the mirror only was white, while the 

 other portion consisted of two images reflected by the green 

 glass and the mirror respectively. The former appeared red 

 by contrast, and the latter was coloured green by transmission 

 through the glass. Thus a white source appeared both white 

 and red at the same instant. The hypothesis of a knowledge 

 of the real whiteness of the surface illuminated partly by a 

 candle and partly by daylight influencing the perception of con- 

 trast colours was refuted by arranging such a surface behind a 

 screen and letting two independent observers view it through a 

 tube showing two semi-circles in juxtaposition. They were 

 misled as to what to expect, but they both immediately described 

 the patches as yellow and sky-blue respectively. These experi- 

 ments tend to confirm Hering's hypothesis, which assumes that 

 when a portion of the retina is stimulated, adjoining portions 

 are affected by a sort of inductive action producing comple- 

 mentary perceptions. 



An interesting note on the variation of the earth's magnetism 

 in the neighbourhood of a hill containing magnetic rocks, by 

 Messrs. Oddone andTranchi, has appeared in the Annali dell' 

 Ufficio Centrale di Meteorologia e Geodinamica (vol. xii. part l). 

 The hill was composed of serpentine, and had, roughly speaking, 

 a lenticular shape, being 1500 m. long and 500 m. broad, with 

 its greatest length north-west and south-east. The declination 

 is the only element up to now observed, and the variation of . 

 NO. 1238. VOL. 48] 



this element along certain lines has been determined by means 

 of a large compass, to which a telescope, moving in a vertical 

 plane, was attached. The needle, about 16 cm. long, had a 

 fine pointer attached, and its position was read by means of a 

 scale engraved on looking-glass. A preliminary series of 

 observations, made on ground where there was no disturbance, 

 showed that this instrument could be depended on to within 

 one or two minutes of arc. The method of observing followed 

 was to set up the instrument, and, looking through the tele- 

 scope, note a series of points, all in a straight line with some 

 distant object, then to clamp the horizontal scale to the tele- 

 scope support, and read the ends of the needle. The instru- 

 ment was then transported to the points which had been noted, 

 and the telescope directed to the distant mark. Then the 

 differences in the readings for the needle gave the differences 

 in the declination at the stations along the line. As an example 

 of the magnitude of the deviations obtained we may give the 

 following set of readings (corrected for diurnal variation), 

 along a line running north-cast from the hill. At the out-crop 

 of the serpentine the reading for the needle was 11° 20'; about 

 100 m. away, 10° 35' ; about 500 m. away 9° 56' 30"; while at 

 a distance of 700 m. it was 9° 50' 30' . In every case they 

 obtained an attraction of the north pointing pole of the needle 

 towards the serpentine, thus indicating that the mass of rock 

 was magnetised with its upper end a south pole. 



M. Felix Leconte has invented a simple form of automatic 

 cut-out, consisting of a cylindrical metal vessel containing mer- 

 cury and closed at the bottom by a plate of iron held up by 

 springs. A copper rod dips into the mercury and forms one 

 terminal, the current passing through the mercury to the metal 

 cylinder, which forms the other terminal. Beneath the piece 

 of iron an electro-magnet is placed, which is connected with an 

 electric battery, whose circuit is closed at any pre-arranged 

 time by a contact fixed to a clock. When this contact is made, 

 the electro-magnet attracts the iron, allows the mercury to 

 escape, and thus breaks the main current. 



A MEMOIR on prehistoric naval architecture of the north of 

 Europe, by Mr. George H. Boehmer, has been issued by the 

 U.S. National Museum, 'Tis "a tale of the times of old, ' and 

 therefore full of interest to the student of history. Further- 

 more, it is written with technical knowledge, and bristles with 

 references, and therefore commands the respect of the scientific- 

 ally-cultured mind. In the memoir the build of thirty ships, 

 discovered in various places, is explained by text and illustra- 

 tion. And the whole discussion indicates that the maritime 

 explorations of the people of the south, the Phoenicians, influenced 

 the character of the naval structures of the ancient inhabitants 

 of Scandinavia. Of all the boats that have been excavated 

 none seem to excel in beauty that found at Gokstad, Norway, 

 in iSSo, and now in the Archaeological Museum of the Royal 

 Frederichs University at Christiania. In the opinion of experts 

 this boat is a masterpiece of its kind, not to be surpassed by 

 aught which the shipbuilding craft of the present age could 

 produce. 



We have received the first number of The Physical Review, a , 

 journal of experimental and theoretical physics conducted by 

 Mr. G. L. Nichols and Mr. E. Merritt, and published for Cor- 

 nell University by Messrs. Macmillan and Co. The new pub- 

 lication is on much the same lines as the Philosophical Magazine. 

 It contains five papers on physical subjects, a few notes, and 

 critical articles on several new books. Mr. Nichols writes on 

 the transmission spectra of certain substances in the infra-red, 

 and Mr. B. W. Snow on the infra-red spectra of the alkalies. 

 The relation between the lengths of the yard and the metre 

 form the subject of a paper by Mr. W. A. Rogers. Messrs. S. 

 Sheldon and G. M. Downing write on the critical current 



