MK. F. E. SMITH OX TIIK COXSTKUCTIOX OF 



connectors could be made of almost any material ; but ebonite was finally 

 chosen as most suitable, owing to the small-grinding action of ebonite with glass. 



The connector designed and adopted is in three parts, and is depicted with two 

 tnl>es clamped together in fig. (5. Very little explanation is required. Through each 



Fig 6. 



of the ebonite collars, A and B, three ebonite screws pass and grip the glass tubes by 

 passing into the grooves previously ground. The collar A is flanged, while B is cut 

 outwardly with a thread for about three-quarters of its length. The connecting 

 piece C rotates freely about the flange of A, so that after the two tubes have been 

 pulled together, the one may be rotated independently of the other. Four large 

 circular holes are also drilled in C, enabling the junction of the tubes to be observed. 

 P is a thin piece of platinum foil serving as a potential point for the mercury 

 column. 



For each standard a special pair of such connectors was made. The outer 

 diameters of the tubes varying somewhat, a good fit in the collars A and B was 

 otherwise impossible. 



With a piece of perforated platinum foil in position as shown, and the tubes well 

 gripped together, such a junction answered the following test. Direct exhaustion 

 with a filter pump through the union reduced the internal pressure to a few 

 centimetres of mercury, a column of mercury 72 centims. high being raised in a glass 

 tube when the barometric height was 74 centims. On severing the connection 

 between the filter pump and junction, the mercury gradually sank, so that at the 

 end of an hour it stood at 60 centims. Possibly some leakage took place through the 

 nihl)er connections. 



The foil employed for the platinum potential points was 0'002 centim. in thickness, 

 and was cut into strips 3 centims. long and about 3 millims. wide. In the centre of 

 each strip, however, the width was greater than this, the foil being cut in the pattern 



