Compressibility of Glass 361 



and of the piezometer indication under H ace computed. 

 Manometer No. 2, when treated simply as a thermometer, 

 showed at atmospheric pressure a rise of one division for a 

 rise of 0-233 C. in temperature. Piezometer K, No. 4, was 

 filled with distilled water, and contained 7-74 cub. centimetres 

 at o and atmospheric pressure. It is made of Ford's glass, 

 though not drawn at the same date as the experimental rod. 

 Dividing the mean apparent contraction of the water in the 

 piezometer by the apparent compressibility of water in glass 

 0-04868, we have for the pressure corresponding to a rise of 

 : divi-ions on manometer No. 2 at 12-5 C. 



H 



0-04868 0-04868 ' 

 = 136-6 atmospheres. 



But this pressure produces a rise of 43-61 divisions on mano- 

 meter No. 2. We have thus for the value of one division on 

 the manometer 



n invert readings of manometer No. 2 into atmo- 

 spheres, \\v have to multiply by 3-132, the difference of the 

 nianuiiu t. i reading under pressure and that at atmosphere 

 pressure, 



In aimtht T series of experiments piezometer K, No. 4. was 

 < >mpared with manometer No. 2, both being at a tempt r.itui. 

 j-5 C., and the foil.. win- r->ult> were obtained as the 

 mean of nineteen ol- OS I 



i rise of manom. j (A) . . 41-35 divisions 



Mean apparent contraction p, i thousand 



ter in piezometer K, No. 4 (H) . . 5*8782 



But from the result- m I d>l. I pressut 



atmospheres 



P - 3-132 x A =3-132x41-35, 

 = 129*5 atmospheres, 



