36 flfiPoRt— 1903. 



Thus, td sdnl Up this part of the Report, it may ba stated that I — 



(a) The original B.A. unit and the stcandard ohm based on it (NoS, 

 3 and 5 of the units concerned) can be recovered from the wire coils 

 of the Association. 



(6) The Board of Trade unit (N^o. i) is now less than the Laboratory 

 unit (No. 5) by -006 per ceiit. 



(c) The Laboratory unit (No. 5) is less tlian the international ohm 

 (No. 2) by -009 per cent. 



(d) The Board of Trade unit is less than the international ohm by 

 •015 per cent. 



(e) The mercury tubes made at the National Physical Laboratory to 

 represent the international ohm are less than those made at the Reichs- 

 anstalt by "0015 per cent. 



This last result must be considered as provisional pending the comple- 

 tion of Mr. Smith's work, but it is clearly highly satisfactory. 



Mr. Smith has also made progress during the year with his investiga- 

 tions into certain of the anomalies shown by Clark cells, but the results of 

 that inquiry are not yet ready for publication. 



The standard condensers of the Association have been frequently in 

 use during the year ; about fifteen condensers have been compared with 

 them. They retain their value in a satisfactory manner, and are conve- 

 i.ient to work with, though possibly some improvement in tlie insulation 

 jaight be desirable. 



A chronograph, purchased with part of the grant made last year, will 

 enable tlie time measurements required in the measurement of capacity 

 to be made with greater accuracy, and hence will permit of greater rigidity 

 in the inquiry as to the permanence of the standards. 



The platinum thermometers made from the stock of wire purchased 

 from Messrs. Johnson and Matthey, which at the time of the last Report 

 Were in course of construction, have been completed, and the behaviour of 

 some of them investigated tliroughout the past year. The resistance-box 

 available was tlie old Callendar-Griffiths box used in the work of Dr. 

 Chree at Kew Observatory, having coils of platinum-silver on the binary 

 system. The contacts are an old form of the Cambridge Instrument 

 Company's type of plug-contact, the cheeks being made of a special white 

 alloy held in round Doulton-ware cups. In measurements with this box 

 not much significance attaches to the third figure of decimals representing 

 hundred-thousandths of an ohm, though the settings could be made to this 

 amount at the lower temperatures. The box resistance-coils were intended 

 for use with platinum thermometers of 1 ohm fundamental interval only, 

 and therefore the two high-resistance thermometers, of 5 ohms funda- 

 mental interval, could not be measured at the sulphur-point ; their 

 systematic investigation has therefore been temporarily postponed. The 

 want of a better box for this work is seriously felt. 



Of the original six thermometers made in August 1902, Nos. 1 to 4 

 aie of 1 ohm fundamental interval, Nos. 1 and 2 being in porcelain and 

 3 and 4 in specially thin Jena glass tubes of internal diameter 8 to 9 mm. 

 and 38 to 40 cm. long. Nos. 5 and 6 are of 5 ohms fundamental interval, 



