MU. \V N SHAW ON HTGROMKTRIC METHODS. 

 TABLE V. 



These six observations gave results agreeing very closely, the mean difference 

 between the tabular saturation pressure and the pressure as deduced from the chemical 

 method being '06 mm only. It will be observed that the same degree of accuracy of 

 agreement is given by the observations in Table IV., which are free from the difficulty 

 of the deposit on the leading tube, the mean of the differences for the first five 

 observations in that table being "056 mm. 



As the temperature readings could not be relied upon to an accuracy much beyond 

 0'l C., it seemed unnecessary to endeavour to press the comparison of the saturator 

 and the chemical method further. 



11. I concluded that I then knew enough about the methods to be justified in 

 expecting the results of the chemical method to agree with the tabular result obtained 

 from the temperature of the saturator within O'l mm., and in regarding the air under 

 those circumstances as being in a known state, and in using it in the investigation of 

 the action of the dew-point instruments. It was, however, necessary to determine 

 whether or not the presence of these instruments affected the air by leakage or other- 

 wise : so that for the succeeding observations I always determined the pressure by the 

 chemical method. First, the REQNAULT was replaced : the result appeared to be 

 disastrous, as the first two observations gave differences between the saturator and 

 chemical method results of 1'OG and '37 respectively, but an investigation disclosed 

 a deposit of moisture in the tube above the tap. The rest of the observations taken 

 are all given in the following table, and notes are appended in cases where some 



disturbing cause was acting. 



TABLE VI. 



