995 



the capillary of the tliermometer the use of cement is now entirely 

 avoided, in the same way as this was effected in the latest thermo- 

 meter for heliiim-temperatiires, (c.f. Comm. No. 1246). In the previous 

 type of thermometer the cement between the steel cap and the 

 glass had evidently been a constant cause of absorption of gas 

 which showed itself in a change of the zero-pressure. ^) 



With the thermometers constructed as they are at present we 

 have not found any change of the zero-pressure which may not be 

 deemed to fall within the limits of accuracy of the measurements 

 (probable error of 02 mm.). 



At the top above the space where the adjustment is made the tube 

 is finished off hemispherically ((/," figg. 3 and 4) and is blown to a 

 capillary (/j" which in its turn is soldered to a steel capillary connect- 

 ingtube 7%," according to Cailletet's method which is used in the 

 construction of a great many apparatus in the laboratory. -) In order 

 to reduce the "noxious space" as much as possible the small bored 

 out steel adjustment-piece e' of Comm. No. 1246 is now ground into 

 the hemispherical space ^,". ') 



Fig. 2. 



^) In the case dealt witli in Comm. No. 95e tliis change amounted to '61 mm. 

 in 19 months and in another case *18 in 4 months. Ghappuis found in his thermo- 

 meter -1 mm. in 3 months. 



'^) On the platinized extremity of the glass capillary a layer of copper is deposi- 

 ted electrolytically. Over this the copper cap is soldered into which the steel 

 capillary has been previously soldered. 



') The small piece is raised into the adjusting-space from below. The tube 



