534 



NATURE 



[September 29, 1898 



unsettled point is the question whether the corona takes part in 

 the sun's rotation. Sir Norman Lockyer explained the con- 

 nection between the spectra of stars and their temperature, and 

 referred to the discovery that the spectrum of the sun's chromo- 

 sphere is similar to that of the principal absorbing layer in 

 7 Cygni, which he characterised as a Rosetta stone of solar 

 and stellar spectroscopy. He showed how the spectra of 

 the various layers of the chromosphere indicate a gradual 

 increase of temperature from without inwards, and announced 

 with reserve, that the Indian photographs suggested that 

 the wave-length of the chief cofonal line required revision. 

 Sir William Crookes suggested the appointment of a joint 

 committee of chemists and physicists to examine quietly the 

 question of solar spectra. Captain E. H. Hills exhibited his 

 photographs of the spectrum of the inner corona. Captain 

 Abney and Prof. Thorpe, who intended to take part in the 

 discussion, were unable to be present at the meeting. 



In meteorology, the Ben Nevis Committee sent a report of ex- 

 tended work, a station having been established at a point half- 

 way up the mountain, and observations taken hourly during a 

 portion of the year. The Committee on Meteorological 

 Photography reported through Mr. Clayden that the work of 

 simultaneously photographing clouds near the sun from two 

 stations in an east and west line had been continued, the results 

 showing that in hot, thundery weather the alto-cumulus and 

 cirro-cumulus clouds attain great heights, sometimes reaching 

 90,000 feet. In order to make observations in the early morning 

 and late afternoon a change of base line to a north and south 

 direction is contemplated. The report of the Seismological 

 Observations Committee deals with many phases of earthquake 

 work, and in introducing it Prof. Milne emphasised the im- 

 portance of securing better accommodation for seismological 

 apparatus. He compared the seismological laboratories of Italy 

 and Japan with the only one of this country, namely his own 

 house at Shide, Isle of Wight. The Sectional Committee has 

 taken steps towards securing the aid of the Government in pro- 

 viding suitable housing for seismological apparatus. The 

 Montreal Meteorological Observatory reports having obtained 

 successfully in McGill University Physical Laboratory records of 

 the temperature on the top of Mount Royal ; the installation of 

 other apparatus recording at a distance is being proceeded with. 

 Prof. Callendar described an application of his platinum ther- 

 mometer as a sunshine recorder, by registering the temperature- 

 difference between a bright and a blackened thermometer. Mr. 

 A. L. Rotch recorded an ascent of the Hargrave kite to a height 

 of 1 1,440 feet at Blue Hill, Mass., U.S.A. Dr. van Rijckevorsel 

 drew attention to a similarity, even in details, between the 

 annual curves of temperature, air-pressure, rainfall, magnetic 

 declination, vertical and horizontal magnetic force. He con- 

 sidered this to be a proof of similarity of origin of magnetic and 

 meteorological phenomena. Mr. Douglas Archibald indicated 

 a classification of weather types in western Europe, lasting for 

 several days, and thus permitting the possibility of extending the 

 present daily forecast. Simultaneous telegraphic reports from a 

 greater number of stations would be necessary. Mr. Hopkinson 

 r«ad a paper on the climate of south-western England. 



Among papers on general physics, Mr. W. N. Shaw exhibited 

 a pneumatic analogue of the potentiometer, in which air-currents 

 set up by gas jets at the lower ends of two tubes take the place 

 of electric currents. The author pointed out its application to 

 some problems of ventilation. Mr. A. W. Warrington described 

 hydrometers of total immersion, which are hydrometers loaded 

 with platinum weights until they are on the point of sinking ; a 

 slight rise of temperature of the liquid then causes them to do 

 so. For liquids, the method is accurate to one part in a million. 

 For solids, a kind of Nicholson hydrometer without tray is used, 

 and the temperature is determined at which the instrument has 

 no weight in water (i) loaded with mercury alone, (2) loaded 

 with the solid and mercury. The results are accurate to one 

 part in 100,000. Mr. W. R. Barker described and exhibited 

 some interesting old weights and measures of Bristol. In 

 sound, if we except Lord Kelvin's communication on the con- 

 tinuity of undulatory theory for sound, elastic-solid and electric 

 waves, the only paper presented was that of Dr. R. J. Lloyd on 

 the articulation and acoustics of the spirate fricative consonants. 

 In this paper the differences between the articulation and 

 resonance of the consonants/, th, h, s, sh and ch are discussed, 

 and the author points out that the first three differ in the length 

 and width of the frictional passage of the throat producing 

 them, whereas the last three require some kind of fore-cavity 



NO. 1509, VOL. 58] 



which modifies and subdues the frictional noises. In the case of 

 s, and sh there is strong resonance from both the fore-cavity and 

 the hinder cavity, the two sounds being differentiated by the 

 second friction against the tips of the lower teeth in producing s. 



We shall take another occasion to refer to the proceedings of 

 the Magetic Conference. 



During the meeting a collection of physical apparatus was 

 exhibited in the physical laboratory of University College by 

 Messrs. J. J. Griffin and Sons. It included an assay balance 

 entirely free from steel, carrying 5 grammes and weighing to 

 0'oooo2 gramme, and a chemical balance weighing to o"oooi 

 gramme, both of which were provided with arrangements for 

 weighing fractions of a gramme without opening the case. 

 Holloway's crucible furnace, Davis' induction coil and X-ray 

 bulbs, were also exhibited, us well as a simple form of apparatus 

 for the measurement of expansion of solids, in which a rod 

 fixed in a water bath between two glass rods is heated and 

 displaces the glass rods ; these pass through the sides of the 

 water bath, and their displacement is measured directly by 

 micrometer screws. The absence of optical devices for measure- 

 ment increases greatly the simplicity of the instrument, which is 

 said to yield fairly good results for lecture purposes. 



MATHEMATICS AT THE BRITISH 

 ASSOC I A TION. 

 C ATURDAY in the British Association week is a holiday for 

 •^ most of the Sections ; the mathematicians and physicists, 

 thus freed from competition, bid for two audiences instead of 

 one, and take papers on mathematics and meteorology in 

 separate rooms. This year the mathematical session, over 

 which Lord Kelvin presided, was very well attended. 



The first paper, read by Colonel Allan Cunningham, was a 

 report on the work of the Committee appointed some years ago, 

 with Lord Kelvin as chairman, for calculating tables of certain 

 mathematical functions. It was explained that a set of tables 

 has been prepared, giving the residues of powers of 2 for all 

 prime moduli less than looo. The plan is much the same as 

 that of Jacobi's Canon Arithmeticus ; but Jacobi uses as base a 

 primitive root of the prime number concerned, which is incon- 

 venient in practical calculations. The tables are now complete 

 in MS., and nothing remains but to print them. It is to be 

 hoped that the Association will see its way to printing them 

 separately in quarto, as their usefulness will be much diminished 

 if they are printed on the smaller page of the Annual Report ; 

 but it seems likely that, partly for financial reasons, they will 

 not be published at all for another year. 



The next paper, "The mathematical representation of 

 statistics," by Prof. Edgeworth, was read in abstract by one of 

 the Secretaries, in the absence of the author ; and the following 

 one, " On the use of logarithmic co-ordinates," by Mr. J. H. 

 Vincent, was taken as read, but is to be published in full in the 

 Annual Report. 



One seldom sees lantern illustrations to a paper read at the 

 mathematical session. But the next two subjects on the list 

 can be treated experimentally as well as mathematically. In 

 the first, " A new method of describing cycloidal and other 

 curves," Prof. Hele-Shaw, of Liverpool, showed a new instru- 

 ment for drawing the curves which can be got by rolling one 

 circle on another. Perhaps its most striking feature is that the 

 radii of the fixed and rolling circles may be as great as we please, 

 their centres not being restricted, as in the ordinary instruments, 

 to the limited range of a drawing board. Thus the radius of the 

 fixed circle may be made infinite, when its circumference be- 

 comes a straight line, and the common cycloid is traced on the 

 paper. 



Another considerable advantage is, that the complete curve 

 required can be drawn in many cases where the ordinary 

 methods would only give a portion of it, or would only give 

 the whole curve after several operations. 



Since an ellipse of any eccentricity may be described by means 

 of a point attached to a circle rolling within another of twice its 

 diameter, it is clear that this instrument can be used for drawing 

 ellipses. It differs from the elliptograph of Messrs. Alexander 

 and Thomson, which depends on the same property, in having 

 two pairs of toothed wheels instead of one ; this improvement 

 gets rid of some of the defects of the older arrangement, with 

 which ellipses can only be got under limited conditions. 



The inventor expressed his opinion that mathematicians would 



