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POPULAR SCIENCE MONTHLY. 



desired to measure, the pressure remaining 

 constant and being that of the atmosphere. 

 As the density of the gas diminishes, the in- 

 terference fringes become displaced. By re- 

 ducing the pressure of the gas in the second 

 or cold tube, the fringes are brought back to 

 their initial position ; and this means that 

 the density is then the same in both tubes. 

 Now, the refraction of a gas is always exactly 

 proportional to its density: the density of 

 the gas in the cold tube is known from its 

 pressure. Hence the density of the hot tube 

 is also known, and from this its temperature 

 is deduced. The method is thought to be 

 well adapted for the measurement of high 

 temperatures, such as those of furnaces, 



• NOTES. 



Abundant testimony is cited by Mr. 

 Walter Hough to the fact that the use of 

 body armor was at one time general if not 

 universal among the North American Indian 

 tribes. The form was usually that of a 

 sleeveless jacket, coat, or wide band, going 

 around the trunk, suspended from the shoul- 

 ders. At the period of its disuse, six types 

 of armor were found on this continent and 

 in contiguous regions — viz., rows of overlap- 

 pmg plates, perforated and lashed ; wooden 

 slats twined together ; wooden rods twined 

 together; bands of skin arranged in tele- 

 scope fashion ; coats of hardened hide ; and 

 cotton-padded armor. 



Prof. Marshall Ward has found from 

 his experimental work of the past few years 

 that the appearance of colonies of the same 

 bacterium, when grown under different con- 

 ditions, are often very unlike. Distinctions 

 of species, therefore, should not be based 

 only upon the appearance of the colony, but 

 should be drawn after study of all the con- 

 ditions of the medium. 



Dr. Treub, director of the botanical gar- 

 dens of Buitenzorg, Java, gave an account, 

 in the British Association, of the formation 

 of hydrocyanic acid in the pangia tree (Fan- 

 ffium edule), and especially of the relation 

 of the acid to the formation of nitrogenous 

 material in plants. He considers that it 

 is, in pangium at least, the first detectable 

 nitrogenous material, and suggested, as an 

 inference, that it is possibly very widely dis- 

 tributed in the vegetable kingdom as a transi- 

 tory substance which becomes rapidly trans- 

 formed into more complex substances. 



The agitation of a proposition to rename 

 one of the boulevards of Paris after Pasteur 

 has developed the fact that besides there 

 being already a rue Pasteur, twenty-one 

 streets in Paris are named after chemists. 

 Among the men thus remembered are Chev- 



reul, Gay-Lussac, Lavoisier, Raspail, Davy, 

 and Berzelius. Seven botanists are thus 

 honored, one alchemist — Nicholas Flannel, 

 of the fourteenth century — and twenty-nine 

 doctors and surgeons. 



We gather from an article in Science 

 that the Conseil Superieur de V Instruction 

 Publique has issued a decree, removing the 

 restrictions upon the admission of American 

 and other foreign students to the French 

 universities, and giving them a status sub- 

 stantially similar to that accorded by the 

 German univergities. 



The gold medal of the Royal Astronom- 

 ical Society has this year been awarded to 

 Dr. S. C. Chandler, of Boston. Dr. Chand- 

 ler's astronomical labors have been exceed- 

 ingly numerous ; but that which has attracted 

 most attention is an investigation showing 

 the probabihty that some small fluctuations 

 of latitude, which had been noticed in par- 

 ticular places, were due to a motion of the 

 earth's axis causing the poles to describe 

 circles, thirty feet in radius, round a center, 

 the period of this motion being about four- 

 teen months. 



A RECENT improvement in the simple 

 pendulum for purposes of measurement is 

 reported as having been made by G. Gugliel- 

 mo. The simple pendulum oscillates about 

 its point of suspension in all directions. The 

 compound pendulum rests on a knife edge, 

 or essentially on two points some distance 

 apart, and therefore oscillates always in 

 the same plane. A bob suspended by two 

 threads will do the same. But for some pur- 

 poses it is highly desirable to have a body 

 oscillating in the same plane and parallel to 

 itself. Sgr. Guglielmo has accomplished this 

 by taking two such bifilar pendulums and 

 joining them by a horizontal rod placed in 

 their plane of vibration. A very useful ap- 

 plication of it is an anemometer designed on 

 this plan. 



The average weekly earnings of laboring 

 men in the United Kingdom are computed 

 in the latest Blue Book to be 27s. 7(/., or 

 £64 ($320) a year. But while this is the 

 average, it is made up by balancing the wages 

 of those who earn more and those who earn 

 less ; and it further appears that twenty-four 

 per cent of the laboring men of the country 

 have less than £1, or $5, per week. 



LuDwiG RiJTiMEYER, the distinguished 

 naturalist, who died on the 26th of last No- 

 vember, was born at Biglen, in the Canton 

 Bern, in 1825. His father was the parish 

 clergyman, and the son intended to follow in 

 his father's footsteps ; but he was from his 

 youth more interested in natural history 

 than in theology. In 1848 he began the 

 study of medicine, and for the rest of his 

 life devoted himself to the study of compara- 

 tive anatomy. 



