Dewar's Method of producing High Vacua. 

 Table VI, 

 Experiment with McLeod Gauge. 

 ^ = -0009 mm. 



509 



t. 





Values of 



P-Po- 





mins. 

 



April 18th. 



April 19th. 



April 20th. 



I Mean. 



•0271 



•0295 



•(-271 



•0279 



5 



•0192 



•0185 



•0179 



•0185 



10 



•0131 



•0131 



•0121 



•0128 



15 



•0100 



•0086 



•0081 



•00S9 



20 



•0069 



•0061 



•0061 



•001)4 



25 



•0053 



•0046 



•0046 



•0048 



30 



•0010 



•0033 



•0040 



•0038 



35 



•0031 



•0026 



•0027 



1 -01)28 



40 



•01)28 



•0022 



(•0022) 



•0024 



45 



•0025 



•0019 



•0018 



•00 JO 



50 





■0016 



•0016 



•0316 



§ 21. The mean values of p—p have been plotted as ordi- 

 nates, with the corresponding values of the time as abscissae 

 in fig. 3, p. 510. It will be seen that the points so obtained fall 

 approximately on a straight line, so that in this case also the 

 relation between the pressure and the time is of the form 

 log (p— Po )=A-\t. 



The value of X in the equation is *0215. 



Table VII. 

 Charcoal Bulb containing 216 gms. of Charcoal. 







Initial 

 Pressure. 



Final 

 Pressure. 



Values of A. 



Baro- 

 meter. 



McLeod. 



April 17th. 



April 18th. 



April 19th. 

 April 20th. 

 April 21st. 

 April 22nd 

 May 8th. 



New bulb attached, strongly 



heated and sealed. 

 Morning 



Afternoon. Exhaust appa- 

 ratus with Meuss pump. 



780-603 mm. 



= 177 mm. 



780-740 mm. 



= 40 mm. 



780-768 mm. 



= 12 mm. 



777-763 mm. 



= 14 mm. 



775— mm. 



=775 mm. 



783-136 mm. 



=647 mm. 



785—155 mm. 



= 630 mm. 



•0095 



•0009 

 •0009 

 •0093 



•0097 



•313 



•220 

 •206 



"1 Mean of 

 [ three 

 [ -0245 



| Ma in of 



y two 



•0216 

 J 



Let in air to atmospheric 

 pressure. 



Apparatus left sealed, since 

 April 22nd. 



