March 23, 1905] 



NATURE 



495 



system which would be readily adaptable to all require- 

 ments, visual or spectroscopic. 



The observations of Sirius have been made under varying 

 conditions, instrumental and otherwise, and a better ac- 

 cordance in the individual results might be obtained by 

 making the observations under uniform conditions. The 

 resulting value, obtained from all the plates, gave the 

 velocity of the system of Sirius as —7-36 km. per second. 

 There is a marked progression among the individual values 

 obtained for the velocity of the primary which is attributed 

 to the effect of orbital motion. The sense of this pro- 

 gression indicates that the positive value of i (the inclin- 

 ation of the plane of the orbit) should be used. The above 

 value, whilst disagreeing with others, agrees very well 

 with the value obtained by Profs. Frost and Adams in 

 1901-2. 



The values of- the radial velocities of the centre of the 

 system and of the primary and secondary components are 

 given in a table, with yearly intervals, for a whole re- 

 volution, i.e. from 1870-09 to 1918-09, the time of the 

 apastron passage being 19 18-5 no. 



Constant Errors in Meridian Observations. — In an 

 address delivered to the astronomy section of the St. Louis 

 International Congress of Sciences and Arts, Mr. J. G. 

 Porter discussed the various sources of error to which 

 meridian observations are peculiarly subject, and proposed 

 various methods whereby the constant errors might be 

 eliminated. 



Among other methods for eliminating the magnitude 

 •error which affects right ascension determinations, he re- 

 commends the one proposed by Prof. Turner wherein the 

 transits would be registered on a regularly moving photo- 

 graphic plate, the reticule wires being replaced by spots of 

 light projected on to the plate at regular intervals from a 

 fixed source. 



Regarding declination observations, the error due to vary- 

 ing refraction is the most important, and Mr. Porter 

 suggests that this might be eliminated by having a per- 

 fected system of fundamental stars well distributed over the 

 ■sphere, from observations of which, on any evening, the 

 •deviation of the actual refraction from the assumed law 

 might be determined and used to correct the observations. 

 Another, more costly, method would be to have a number of 

 observatories widely distributed in latitude, so that zenith 

 observations, where refraction is non-effective, of more 

 stars might be made. Mr. Porter considers the solution of 

 this constant error difficulty in meridian observations to be 

 one which is eminently suitable for international coopera- 

 tion (Popular Astronomy, No. 3, vol. xiii.). 



THE NATIONAL PHYSICAL LABORATORY. 

 /^\ Friday last the annual general meeting of the govern- 

 ^^^ ing body of the National Physical Laboratory was 

 lield at that institution, when the report of work done 

 in 1904 was received and the programme of work pro- 

 posed for the forthcoming year approved. A number of 

 guests were invited to meet the members of the general 

 board and inspect the laboratory, .'\mong those present 

 were about thirty Members of Parliament, several colonial 

 agents-general, and a representative gathering of leading 

 physicists and engineers. 



in the 45-page report submitted by the director. 

 Dr. Glazebrook, are found particulars regarding the various 

 researches and tests carried out during the past year, with 

 special reference to the newer developments. The test work 

 at Bushy for the year shows a marked growth, the total 

 number of separate tests made having increased from 1330 

 In 1903 to 1906 in 1904, the increase being spread over 

 almost alj the different departments of the laboratory. 

 These figures are distinct from the work of Kew Ob- 

 servatory, where in all more than 26,000 instruments were 

 ■verified duriiig the year. 



In the engineering department. Dr. Stanton has made 

 considerable progress with the research on the distribution 

 of wind pressure over large areas, which forms a con- 

 tinuation of the important work embodied in his paper read 

 at the Institution of Civil Engineers last session. A steel 

 tower fifty feet high has been erected in the grounds, 



NO. 1847, ^OL. 71] 



carrying large and small pressure plates with the necessary 

 gauges. From the general results of the observations 

 made it would appear that the distribution of pressure on 

 the windward side of a large plate in the open air falls 

 off more rapidly from the centre to the sides than in the 

 case of a small plate, but that the ratio of the pressures 

 on the windward and leeward sides appears to be practic- 

 ally the same in both cases. 



The research on the specific heat of superheated steam 

 by the continuous flow method has been continued by Mr. 

 Jakeman, who has been mainly occupied in contending with 

 certain experimental difficulties, such as the attainment of 

 sufficiently high insulation between the various parts of the 

 electrical superheater, especially at low superheats. Some 

 preliminary figures have been obtained which do not appear 

 to confirm the rapid rise in specific heat shown by the 

 results of some recent observers. 



A testing machine for studying the effect of alternating 

 stresses of varying periodicity on engineering materials has 

 been constructed and w-as described in last month's 

 Engineering by Dr. Stanton. It has already been used on 

 a set of nickel-steel specimens, which are the basis of a 

 research in the metallurgical department. 



A new building has been erected to house the new 

 standard leading-screw machine, which is now at work. 

 Several standard screws have been cut and measured for 

 use in Government arsenals. 



Dr. Chree, at the observatory department, has been 

 occupied with some important investigations on terrestrial 

 magnetism, and the measurement and tabulation of some of 

 the old Kew magnetic records. The men of science of the 

 British Antarctic Expedition have, since their return in 

 September last, had the opportunity of again comparing 

 with recognised standards many of their instruments, and 

 arrangements have been made for cooperation with them in 

 the reduction of the mass of magnetic and meteorological 

 data they brought home w-ith them. 



In the phvsics department numerous researches have been 

 in progress. We have only space for mentiop here of 

 some of the more important. Dr. Harker, in the ther- 

 mometry division, has been occupied with preliminary work 

 on which it is hoped may ultimately be based some new 

 direct electrical method of very high temperature measure- 

 ment. With this object he has undertaken a study of the 

 resistance and thermoelectric properties of solid electrolytic 

 conductors such as are used in Nernst lamps. The exist- 

 ence at high temperatures of large thermoelectromotive 

 forces between rods of the various earths made up as 

 ordinary thermojunctions has been securely established by 

 direct electrometric methods, and a new form of electric 

 furnace has been designed capable of continued use at 

 temperatures above 2000° C. By means of these furnaces 

 and a number of thermojunctions of widely different pro- 

 perties, a careful re-determination of the melting point of 

 platinum was made. More than sixty determinations con- 

 corded in giving a value which differs considerably from 

 that now accepted. The results of this work are embodied 

 in a paper iust sent in to the Royal Society. 



The research on the specific heat of iron, which has 

 been extended to temperatures above 1100° C, is complete, 

 and will shortly be published. 



In the electrical standards department, Mr. Smith has 

 been mainly occupied with work on the standard ampere 

 balance designed by the late Prof. Viriamu Jones and Prof. 

 Ayrton for the British .Association committee on electrical 

 standards. The weighing mechanism was constructed by 

 Mr. Oertling, and the four marble cylinders carrying the 

 coils have been successfully wound and insulated at the 

 laboratory. On each cylinder are two double helices of 

 bare copper wire. Though the air space between the con- 

 secutive turns is less than o-oo6 inch, an insulation resist- 

 ance over 30,000 megohms was finally secured for each 

 of the coils. Many accessories have been constructed, and 

 the outlook for a speedy determination of the absolute unit 

 of current to at least one decimal place further than hitherto 

 attained is very hopeful. 



In electrotechnics, Mr. Paterson has installed large cells 

 for ammeter verification, and for alternate current measure- 

 ments a specially constructed set of Mr. Addenbrooke's in- 

 struments, and a Kelvin voltmeter with circular scale of 

 ■2i metres radius. In photometry have been included in- 



