98 



DISPLACEMENT INTERFEROMETRY APPLIED TO 



correction ; and it is probably not all that a region of fairly constant temper- 

 ature (thermostat) is able to warrant. At the individual observations or 

 kinks, the irregularity still exceeds o. i per cent and there has not been much 

 advance in precision. 



TABLE 4. Behavior of divers B'" and F'", inverted pycnometers. MB = 15.648 grams; 



Mr = 16.399 grams; h a = 12 cm; h r = 9.1 cm. 



However, one possible improvement is yet available, and that consists in 

 diminishing the area of contact (a and b, fig. 114) between the air and water, 

 within the diver. Such alteration would diminish the opportunity for solution 

 and consequent transportation. The probability of a material advantage to be 

 gained in this way is sustained by the data of the next paragraph, in which a 

 diffusion or solutional coefficient is nearly eliminated. 



81. The diffusion of air through water in the lapse of years. In 1912, I 

 put up a U-tube of the form shown in figure 117, containing a charge of water 

 w w' below the air-chambers a, a', both at nearly atmospheric pressure. The 

 tubes were sealed by fusion cautiously to avoid the presence of flame gases in 

 aa'. They were then put away in a dark vault of nearly constant temperature 

 (for short-time ranges) to be examined from time to time as to the displacement 



