It consists of a three-necked Wolff bottle having provision at one of its necks for exhausting the air from the bottle. The reverse neck is provided with a gauged glass tube dipping into a porcelain crucible containing mercury, thus acting as a manometer. The middle neck is fitted to accommodate two ground glass plates. Both these plates are provided with a central orifice one millimeter in diameter. Between the plates is placed a small section of paint film. The plates may be pressed together or clamped together and placed over the middle neck of the bottle, a close contact being made with Canada balsam. As the air is exhausted from the bottle, the mercury in the tube will rise and continue in its ascent until the film, which is exposed to atmospheric pressure, has offered it maximum resistance, which is shown by the breaking point. This point is observed on the manometer and the result expressed in centimeters of mercury. =Table of Film Testing Results.= By means of the Perry film-testing apparatus, described in the above, interesting results have been obtained, which are embodied in the following table: COMPARATIVE STRENGTHS OF FILMS AS OBTAINED BY THE BREAKING MACHINE ============================+=========+==========+===========+======== |No. Coats| Pressure | Thickness | Stretch ----------------------------+---------+----------+-----------+-------- 1. Zinc oxide | 3 | 33.2 | 0028 | .30 2. Zinc lead | 3 | 32.7 | 0034 | .35 3. Asbestine | 3 | 28.0 | 0045 | .15 4. Sublimed white lead | 3 | 17.9 | 0024 | .38 5. Barytes | 3 | 13.3 | 0042 | .33 6. Lithopone | 3 | 13.1 | 0024 | .49 7. Whiting | 3 | 13.0 | 0033 | .32 8. Quick process white lead| 3 | 11.3 | 0025 | .38 9. Gypsum | 3 | 10.8 | 0039 | .29 10. China clay | 3 | 10.8 | 0035 | .16 11. Silex | 3 | 9.6 | 0032 | .32 12. Blanc fixe | 3 | 8.5 | 0030 | .28 13. Corroded white lead | 3 | 7.3 | 0020 | .33 14. Barium carbonate | 3 | 7.2 | 0028 | .16 ============================+=========+==========+===========+========