October 4, 1900J 



NATURE 



563 



bulb open to the air and containing a little mercury. When a 

 reading is required, the instrument is inverted so that a column 

 of mercury runs down the tube towards the first bulb and com- 

 presses the air in it. From the position taken up by the end 

 of this column, when the compressed gas has cooled to its 

 original temperature, the original pressure of the gas can, if 

 the gas is dry, be found. In the instrument this pressure is 

 read off on a scale alongside the tube. The air enclosed is dried 

 by passage through a plug containing calcium chloride. The 

 instrument is very compact and portable. 



Mr. A. L. Rotch contributed a note on the use of kites for 

 meteorological observations at Blue Hill Observatory, Mass. 

 Observations with kites have been made up to l6,ooo feet above 

 sea level, and have been reduced and published in abstract in 

 Nature, July 12 and August 9. 



Captain Campbell Hepworth exhibited and discussed some 

 charts illustrating the weather of the North Atlantic Ocean 

 during the winter of 1898-9. At sea this period was one of 

 violent storms, while the weather in America was exceptionally 

 cold, and in Europe very mild. Some of the cyclones crossed 

 quickly from the American coast to the British Isles, while 

 others — in particular the worst one in February — made slow 

 progress. Much damage was done to shipping, and even powerful 

 vessels, like the Lucania and the Fiirst Bismarck, were unable 

 to make headway, and arrived at their destinations several days late. 

 Mr. J. W. Thomas, in a communication on the physical 

 effects of wind in towns and their influence upon ventilation, 

 pointed out that the well-known effect of currents of air in 

 diminishing the air pressure in vessels across the openings of 

 which they passed, was generally neglected by writers on ventil- 

 ation. A gusty wind, during its period of maximum velocity, 

 reduces the air pressure in a room by the withdrawal of air 

 through the chimney. When the wind lulls, the air passes down 

 the chimney into the room, and the chimney "smokes." 



Mr. J. Ilopkinson gave an account of the rainfall of the 

 northern counties of England. The means for the ten years 

 ending 1890 are : — 



Cumberland, 57*9; Westmoreland, 55*9; Derbyshire, 40*2 ; 

 Lancashire, 383; Yorkshire, 33-4 ; Cheshire, 31*3; North- 

 umberland, 31 "o; Durham, 28" i ; Nottinghamshire, 24*4 ; Lin- 

 colnshire, 24*3 inches per annum. These numbers show dis- 

 tinctly the effect of highlands in increasing the average rainfall. 

 Mr. G. E. Petavel described the apparatus he is using in his 

 experiments on the explosive pressures of gases. He measures 

 the maximum pressure attained in his explosion vessel by means 

 of a piston which is forced out and makes a telephone contact 

 if the pressure exceeds a certain value. By means of the com- 

 pression of a cylinder he measures also the rate of change of the 

 pressure. He finds that in the case of hydrogen and oxygen 

 the maximum is about ten times the initial pressure, and that 

 inert gases delay but do not greatly diminish the maximum 

 pressure. 



Mr. J. W, Gifford gave an account of a quartz- calcite lens he 

 had designed, having the same focal length for wave-lengths 

 5607 and 2761, which he considers may be taken as the centres 

 of the visual and photographic portions of the spectrum 

 respectively. 



Messrs. A. Dufton and W. M. Gardner exhibited at the 

 Technical College an arrangement they had devised for the pro- 

 duction of an artificial light of the same character as daylight. 

 Such an artificial light has been much wanted by those engaged 

 in dealing with coloured stuffs, and the practical demonstration 

 given by the authors showed that they have successfully supplied 

 this want. They use an enclosed arc lamp, and surround the 

 translucent bulb of the lamp by a tank containing a solution of 

 copper sulphate of the proper strength, or by a box with sides 

 of glass of the same colour and the requisite thickness. 



Mr. H. Ramage described his method of investigating corre- 

 spondences between spectra. He takes wave frequency as 

 abscissae, and atomic weights of the elements whose spectra are 

 to be compared as ordinales, and joins by lines the "corre- 

 sponding " points of the various spectra. These lines are in 

 general curved, and in the case of the components of a doublet 

 their distance apart increases with the atomic weight. If the 

 squares of the atomic weights are taken as ordinates, they 

 become straight lines intersecting on the axis of wave frequency. 

 He proposes, therefore, to introduce a term aW^, where a is a 

 constant, and W the atomic weight, into Rydberg's formula 



which will thus become « = «o-aW'^ 



NO. 1614, VOL. 62] 



_ No _ 

 (in - ixf 



Mr. G. J. Burch exhibited an experiment on simultaneous 

 contrast. One half of the slide of a stereoscope consists of blue 

 and the other of red glass. By means of diffraction gratings in 

 the eyepiece of the stereoscope, two spectra are produced which 

 appear to cover two patches of black paper on the two glasses. 

 Under these circumstances, that seen by the eye which looks at 

 the red glass appears to lack red, the eye being partially blinded 

 for red, the other for a similar reason lacks blue. In Mr. Burch's 

 opinion these facts confirm the views of Thomas Young on 

 colour contrast. 



The Committee for improving the method of determining 

 Magnetic Force on Board Ship reported that an instrument had 

 been constructed according to the designs of Captain Creak, 

 which gave promise of overcoming many of the difficulties met 

 with in using Fox's circle. 



The work of the Committee on Radiation in a Magnetic Field 

 had been interrupted by the death of Mr. Preston, but the com- 

 mittee now proposed to issue copies of Preston's photographs 

 showing how the various types of lines are affected by the 

 magnetic field. 



The Electrica 1 Standards Committee reported that the standai ds 

 had been removed to Kew, where an outbuilding had been fitted 

 up for the temporary use of the committee of the National 

 Physical Laboratory. The sub-committee on platinum thermo- 

 metry has decided that platinum thermometers shall be con- 

 structed of a selected sample of platinum wire, and be used as 

 standards for high temperature measurements. The selection of 

 wire is still under the consideration of the committee. Arrange- 

 ments have been made for the construction of a mercury resist- 

 ance standard and an ampere balance. The Committee approves 

 of the adoption of the names Gauss and Maxwell for the C.G.S. 

 units of magnetic field and flux respectively. 



Mr. R, S. Whipple gave an account of his improved standard 

 resistance coils. Alongside the platinum-silver wire of the 

 standard coil a second wire of platinum is wound. The differ- 

 ence of resistance of the two coils depends on their tempera- 

 ture, which may therefore be regulated to have any required 

 value. Dr. R. T. Glazebrook pointed out that the method had 

 been used by Messrs. Crompton in constructing their standard 

 resistances. 



Mr. E. H. Griffiths described the form of Wheatstone bridge 

 he has devised for determining the freezing-points of dilute 

 solutions by platinum thermometry. A platinum thermometer 

 of about 18 ohms resistance placed in the solution, and another 

 similar one in ice, form two of the arms of a Wheatstone bridge. 

 The rest of the bridge is of platinum. The galvanometer is 

 connected to the bridge by means of two sliders, each of which 

 moves along a pair of platinum wires, one of the pair forming 

 part of the bridge, and the other connected permanently to the 

 galvanometer. The readings of these sliders for a balance 

 determine the difference of temperature of the two thermo- 

 meters. Using a Paschen galvanometer giving a deflection of 

 I mm. on a scale i metre distant for a current of io~^- ampere, Mr. 

 Griffiths can determine temperature to one-millionth of a degree 

 centigrade. Mr. R. Threlfall pointed out that although the 

 temperature of the platinum wire of the thermometer could be 

 determined to this degree of accuracy, the temperature of the 

 solution could not. In reply to Dr. Glazebrook, Mr. Griffiths 

 stated that the mercury contacts in Carey Foster's method 

 introduced changes which prevented this high degree of accuracy 

 being attained with it. 



Prof. F. G. Baily described a lecture-room form of volt and 

 ammeter which he had devised. By means of a series of resist- 

 ance coils all contained in a small box, the deflections of a 

 galvanometer of the d'Arsonval type are made to correspond to 

 simple multiples or submultiples of a volt or an ampere. 



Prof. W. B. Morton communicated some results he had ob- 

 tained by applying J. J. Thomson's and Sommerfeld's solution 

 of the propagation of an electric wave along a single wire, to the 

 approximate solution of cases of several parallel wires, some of 

 which may be returns, when the square of the ratio of the radii 

 of the wires to their distances apart may be neglected. His 

 results agree with the more complete investigations given by 

 Mie in the June number of the Annakn der Physik. 



A communication from Mr. S. H. Burbury on the vector 

 potential of electric currents in a field where disturbances are 

 propagated with finite velocity, was, in the absence of the author, 

 taken as read. There are difficulties in the way of the usual 

 definition of the vector potential due to electric currents when 

 these currents are changing. These difficulties Mr. Burbury 



