Mr. Meem's paper is very valuable in that it presents some unusual phenomena, but many of the conclusions drawn therefrom cannot be accepted without further demonstration. FRANCIS W. PERRY, ASSOC. M. AM. SOC. C. E.--Pressure-gauge observations on a number of pneumatic caissons recently sunk, through various grades of sand, to rock at depths of from 85 to 105 ft. below ground-water, invariably showed working-chamber air-pressures equal, as closely as could be observed, to the hydrostatic pressures computed, for corresponding depths of cutting-edge, as given in Table 2. These observations and computations were made by the speaker in connection with the caisson foundations for the Municipal Building, New York City. TABLE 2.--EQUIVALENT FEET OF DEPTH BELOW WATER PER POUND PRESSURE. Pressure, |Equivalent |Equivalent |Observed | in |feet of |elevation |pressure. | pounds. |depth. |for water | | | |at--6.85. | | |___________|_____________| | | | | | |M.H.W. |Ground-water.| | __________|___________|_____________|______________| | | | | 1 | 2.31 | 9.06 |Practically | 2 | 4.63 | 11.48 |the same as | 3 | 6.94 | 13.79 |computed | 4 | 9.25 | 16.10 |for | 5 | 11.57 | 18.42 |ground-water. | 6 | 13.88 | 20.73 | | 7 | 16.19 | 23.04 | | 8 | 18.50 | 25.35 | | 9 | 20.82 | 27.67 | | 10 | 23.13 | 29.98 | | 11 | 25.44 | 32.29 | | 12 | 27.76 | 34.61 | | 13 | 30.07 | 36.92 | | 14 | 32.38 | 39.23 | | 15 | 34.70 | 41.55 | | 16 | 37.01 | 43.86 | | 17 | 39.32 | 46.17 | | 18 | 41.63 | 48.48 | | 19 | 43.95 | 50.80 | | 20 | 46.26 | 53.11 | | 21 | 48.57 | 55.42 | | 22 | 50.89 | 57.74 | | 23 | 53.20 | 60.05 | | 24 | 55.51 | 62.36 | | 25 | 57.82 | 64.67 | | 26 | 60.14 | 66.99 | | 27 | 62.45 | 69.30 | | 28 | 64.76 | 71.61 | | 29 | 67.08 | 73.93 | | 30 | 69.39 | 76.24 | | 31 | 71.70 | 78.55 | | 32 | 74.01 | 80.86 | |