522 



NA TURE 



[April 2, i( 



units, for which — in conjunction, as regards some parts 

 of the worlv, with Prof. Ayrton, Mr. Mather, and Dr. 

 Lowry — Mr. F. E. Smith is responsible, and which, with 

 an earlier paper on mercury resistance standards, embody 

 the results of the work of the electrical standards depart- 

 ment from the foundation of the laboratory. We shall, 

 no doubt, have occasion to refer more particularly to these 

 three papers in dealing- with the " Collected Researches " 

 of the laboratory; vols. iii. and iv. of which are now ready 

 for issue. The ampere balance, planned originally by 

 \'iriamu Jones and .Ayrton, the electrical part of which 

 was constructed at the laboratory, with such modifications 

 of the original design as experience showed to be neces- 

 sary, under Mr. Smith's supervision, has given results 

 " far exceeding that secured in any absolute determination 

 of any electrical unit. . . . The balance was intended to 

 give the ampere to i part in 10,000, but about i part in 

 50,000 appears to have been attained. A little uncertainty 

 exists as to the value of g and the axial length of the 

 coils ; the latter uncertainty may shortly be removed " (by 

 the construction of new coils). 



The work on \\v mmparison of various forms of silver 



of insulali 



materials, 



voltameter has led to results of the same order of accuracv. 

 Mr. -Smith has shown that under specified conditions all 

 the different types of voltameter experimented with give 

 identical results for the electrochemical equivalent to 

 within 2 parts in 100,000. In a suggested specification 

 for the international ampere the Rayleigh form is recom- 

 mended as the easiest to erect. 



The paper on the Weston cadmium cell summarises the 

 results of all the observations made at the National 

 Physical Laboratory, and establishes the reproducibility 

 and constancy of the cell. The results of comparisons 

 between American, French, German, and English cells are 

 given in the report, and show that standard cadmium cells 

 <van be set up by different experimenters with different 

 materials to agree within a few parts in 100,000. 



The results obtained, in these researches and in those 

 simultaneously carried on in the standardising institutions 

 at Washington, Paris, and Berlin should make the way 

 clear for the International Conference on Electrical Units 

 to be held in Ixindon probablv this vear. Mr. Smith is 

 to be congratulated on having placed the laboratory in the 



NO. 200s, VOL. 77] 



forefront of the institutions engaged in this work. The 

 construction of the Lorentz apparatus, to be presented to 

 the laboratory by the Drapers' Company, has been already 

 commenced, and may perhaps be completed within the 

 current year. 



The research work of other departments must be dealt 

 with more shortly. Mr. Campbell has published a valu- 

 able series of papers on mutual inductances : construction 

 of standards, and methods of measurement. These latter 

 include the use of a novel form of vibration galvanometer. 

 Dr. Harker's high-temperature work has been delayed by 

 his illness, but a new type of high-temperature furnace 

 has been devised which promises well for the uniform 

 heating of fairly large objects to about 2500° C. In the 

 metrology department much time has been devoted to the 

 development of methods of measurement of screws, and 

 a 4-metre standard bar has been divided and calibrated. 

 Mr. Hunter, in the optical department, has devised a 

 method of considerable interest for the measurement of 

 definition, more especially of photographic lenses. In the 

 electrotechnics department a research on the dielectric 

 undertaken for the 

 Engineering Stand- 

 a r d s Committee, 

 has been delayed by 

 the failure of the 

 ioo,ooo-volt trans- 

 former under con- 

 struction. 



In the engineering 

 department, D r. 



Stanton has com- 

 pleted some import- 

 ;uit researches. The 

 wind-pressure work 

 has established in- 

 teresting results as 

 regards the relative 

 pressures on large 

 and small plates, 

 which receive re- 

 markable confirma- 

 tion from the ex- 

 periments of M. 

 Eiffel. The com- 

 parison of open-air 

 results on large 

 models with those 

 obtained earlier for 

 small models shows 

 that the values for 

 large surfaces in the 

 <ipen can be inferred 

 with accuracy from 

 observations in the 

 1 iboratory. Other 

 researches carried 

 Instill' I. 111. ,11-. ""' ^^^ ■^■'h the 



resistanceof 

 materials under re- 

 peated stresses and blows in four forms of impact testing 

 machine, and the elastic limits of material under alter- 

 nating stress. 



In the new department for metallurgy Mr. Rosenhain 

 has been very active, and at least three researches of 

 first-rate importance were in progress during the year 

 under his direction. The most interesting is perhaps' the 

 investigation of the alloys of aluminium, copper, and 

 manganese, in continuation of the work carried out bv 

 Dr. Carpenter on the aluminium-copper alloys, which 

 appears in vol. iii. of the " Collected Researches." For 

 the purpose of the metallurgical research an ultra-violet 

 microscopic outfit has been installed for obtaining photo- 

 micrographs at magnifications up to 3600 diameters. 



The report is followed by an appendix, which gives 

 some details as to the equipment of the electrotechnical 

 laboratory (including the department for photometry). 

 Much yet remains to be done to complete the equipment 

 of this building, but the arrangements have been planned 

 with the view of meeting the demands which are likely 

 to arise, and the account given is of no little interest and 



