NA 7 URE 



[March 25, 1909 



which is the telescope for taking the readings, while a 

 series of switches allows of temperature regulation. By 

 means of a handle on the left of the desk, connected by a 

 flexible shaft to the cage carrying the thermometers, the 

 carte can be rotated so as to bring the thermometers 

 successively into the field of view-. 



The bath on the right in the illustration is reserved for 

 the comparison of standards. It is of the same general 

 type as above described, but is being fitted with a telescope 

 carried on a traversing support fixed to the bath itself, 

 giving greater rigidity, and thus allowing the employment 

 of a higher magnification. In addition there are a bath 

 for very long thermometers, oil and nitrate baths for the 

 higher temperatures, zero-point apparatus for ordinary and 

 standard thermometers, and steam-point apparatus. The 



Fig. 2. — Steam Point .Apparatus for Standard Thermometers. 



steam-point apparatus for standard thermometers is of the 

 form designed by Chappuis, and is shown in Fig. 2. The 

 upper part can be turned into a horizontal position, so 

 that observations can be made with the thermometer either 

 horizontal or vertical, as required for determination of 

 pressure coefficients. A second steam bath of similar 

 form, but not arranged to tilt, serves for ordinary work. 



The work of the thermometry division has also included 

 the equipment, for work at very high temperatures, of the 

 new electric furnace room. Much attention has been given 

 to the perfecting of furnaces, and some interesting figures 

 are printed in the report showing the increased efficiency 

 obtained in the ordinary platinum-foil wound type with 

 improved construction and lagging. The power required to 

 maintain a temperature of 1350° C. has been reduced from 



NO. 2056, VOL. 80] 



3300 watts to 1400 watts, the new furnace being at the 

 same time of greater internal capacity than the old. A 

 new type of spiral carbon-tube furnace has been devised, 

 of which a description will be published shortly, and much 

 preliminary work has been done with a view to the greatly 

 needed investigations into the different methods employed 

 in measuring temperatures up to 2000° C. 



The chief item of research work completed during 1908 

 was an investigation, in which Mr. F. P. Sexton assisted^ 

 into the effect of pressure on the boiling point of sulphur. 



In the electrical standards division much time was spent 

 in intercomparison of standards with those of other labora- 

 tories, and the excellent work accomplished by Mr. F. E. 

 Smith was of great value in connection with the Inter- 

 national Conference on Electrical Units, held in London in 

 October. The papers published during 1908 in- 

 clude an account of the secular variations in the 

 laboratory standards of resistance, and of the 

 effect on manganin resistances of atinospheric 

 humidity. Vol. v. of the " Collected Researches " 

 contains also a paper describing an improved 

 procedure for setting up mercury standards of 

 resistance. In addition to this work, good pro- 

 gress has been made in the construction of the 

 Lorenz apparatus for the determination of the 

 ohin in absolute measure, which is being pre- 

 sented to the laboratorv by the Drapers' Com- 

 pany in memory of the late Prof. Viriamu Jones. 

 Mr. Campbell has continued his work on self- 

 and mutual-inductance standards. Of special 

 interest is the method he has devised for the 

 direct comparison of a mutual inductance and a 

 resistance, from which may be made a deter- 

 mination of the ohm in absolute measure. A 

 preliminary account of the method has been pub- 

 lished in the Proceedings of the Royal Society, 

 and it seeins possible that in the further experi- 

 ments to be made a high degree of accuracy in 

 the absolute determination may be attained. 

 Valuable work has also been done in setting up 

 standards for the determination of oscillation fre- 

 quencies in wave telegraphy. 



From the optics department, a paper by Mr. 

 Hunter describing an apparatus for determining 

 the intensity curve for the image of an " edge " 

 formed bv' an optical system was recently 

 read before the Royal Society. Of general 

 interest also is a new apparatus for testing the 

 speeds and efficiencies of photographic shutters, 

 the method consisting in photographing a spot 

 of light reflected from the mirror of one of Mr. 

 Campbell's vibration galvanometers. The time is 

 determined from the known frequency of the 

 galvanometer, and a satisfactory trace is obtain- 

 able even for very high shutter speeds, which can 

 thus be determined with considerable accuracy. 

 Work which has been in progress for some time 

 on the standardisation of oculists' cases of trial 

 lenses was completed during the year, and the 

 testing and certifying of such trial cases is now 

 *^ regularly undertaken by the laboratory. The 

 testing 'of microscope objectives is also under 

 consideration. 



In the electrotechnics building the chief 

 addition to the equipment is a 100,000-volt 

 transformer by the Westinghousc Co., -vyhich 

 was recently installed, and is now working satisfac- 

 torily. This will be employed in the continuation^ of 

 a research on insulating materials, while _ an investiga- 

 tion into the dielectric strength of ebonite of 

 compositions is already in progress. A large 

 of test work on alternating-current instruments \vas 

 dealt with during the year, and the equipment for 

 such work has been greatly improved. A new electro- 

 static wattmeter, constructed in the laboratory workshop, 

 deserves special mention, as well as a series of manganin 

 water-cooled tube resistances with a device for bringing 

 the voltage drop at their terminals into phase with the 

 current passing through them. 



In the photometry section, also, good progress has been 

 made, especially in the ' ' ' '" '""'■ 



various 

 amount 



rangements for life tests on glow 



